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Claudio FONTANESI

Professore Associato
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2024 - Chiral Recognition: A Spin‐Driven Process in Chiral Oligothiophene. A Chiral‐Induced Spin Selectivity (CISS) Effect Manifestation [Articolo su rivista]
Stefani, Andrea; Salzillo, Tommaso; Mussini, Patrizia Romana; Benincori, Tiziana; Innocenti, Massimo; Pasquali, Luca; Jones, Andrew C.; Mishra, Suryakant; Fontanesi, Claudio
abstract

In this paper it is experimentally demonstrated that the electron-spin/molecular-handedness interaction plays a fundamental role in the chiral recognition process. This conclusion is inferred comparing current versus potential (I-V) curves recorded using chiral electrode surfaces, which are obtained via chemisorption of an enantiopure thiophene derivative: 3,3 & PRIME;-bibenzothiophene core functionalized with 2,2 & PRIME;-bithiophene wings (BT2T4). The chiral recognition capability of these chiral-electrodes is probed via cyclic voltammetry measurements, where, Ag nanoparticles (AgNPs) capped with enantiopure BT2T4 (BT2T4@AgNP) are used as the chiral redox probe. Then, the interface handedness is explored by recording spin-polarized I-V curves in spin-dependent electrochemistry (SDE) and magnetic-conductive atomic force microscopy (mc-AFM) experiments. The quality of the interfaces is thoroughly cross-checked using X-ray photoemission spectroscopy, Raman, electrodesorption measurements, which further substantiate the metal(electrode)-sulfur(thiophene) central role in the chemisorption process. Spin-polarization values of about 15% and 30% are obtained in the case of SDE and mc-AFM experiments, respectively.It is demonstrated that probing the handedness of a chiral system (here a chiral-electrode-surface/solution interface) by using a spin-polarized current, allows for chiral recognition. This conclusion is inferred by tight comparison with cyclic voltammetry results, where the handedness of the "chiral-electrode-surface/solution interface" is recognized by using an enantiopure chiral redox couple.image

2024 - Electrochemical growth of PAH-dendrimers supramolecular films. An integrated experimental-theoretical approach [Articolo su rivista]
Bonechi, M.; Marchetti, A.; Giurlani, W.; Vanossi, D.; Pasquali, L.; Campidelli, S.; Fontanesi, C.; Innocenti, M.
abstract

The electrochemical oxidation of a polyphenylene-based dendrimer containing 96 sp2 carbon atoms (PPD) allows obtaining a more extended conjugated carbon framework, polymer PPD (pPPD), starting from the parent fused- benzene-based PPD. The structure and electronic properties of the polymeric thin film obtained by electrochemical oxidation have been characterized by Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy. Structural properties of the thin film formed upon electrochemical oxidation of PPD, are characterized by Matrix-Assisted Laser Desorption/Ionization (MALDI-TOF) and Gel-Permeation Chromatography (GPC) measurements. The degree of order of the layers as well as the virtual, and occupied, electronic states are addressed and exploited to obtain information on conjugation and oligomer size within the polymeric pPPD film. The experimental results are compared with DFT, B3LYP/6–31G(d), calculations. The overall results suggest that the thin film formed on the electrode surface is mainly formed by PPD dimer and trimer upon electrochemical oxidation.

2023 - Analytic procedure for the evaluation of copper intermetallic diffusion in electroplated gold coatings with energy dispersive X-ray microanalysis [Articolo su rivista]
Giurlani, W.; Biffoli, F.; Fei, L.; Pizzetti, F.; Bonechi, M.; Fontanesi, C.; Innocenti, M.
abstract

2023 - Challenges in the Direct Detection of Chirality-induced Spin Selectivity: Investigation of Foldamer-based Donor-Acceptor Dyads [Articolo su rivista]
Privitera, Alberto; Faccio, Davide; Giuri, Demetra; Latawiec, Elisabeth I.; Genovese, Damiano; Tassinari, Francesco; Mummolo, Liviana; Chiesa, Mario; Fontanesi, Claudio; Salvadori, Enrico; Cornia, Andrea; Wasielewski, Michael R.; Tomasini, Claudia; Sessoli, Roberta
abstract

Over the past two decades, the chirality-induced spin selectivity (CISS) effect was reported in several experiments disclosing a unique connection between chirality and electron spin. Recent theoretical works highlighted time-resolved Electron Paramagnetic Resonance (trEPR) as a powerful tool to directly detect the spin polarization resulting from CISS. Here, we report a first attempt to detect CISS at the molecular level by linking the pyrene electron donor to the fullerene acceptor with chiral peptide bridges of different lengths and electric dipole moment. The dyads are investigated by an array of techniques, including cyclic voltammetry, steady-state and transient optical spectroscopies, and trEPR. Despite the promising energy alignment of the electronic levels, our multi-technique analysis reveals no evidence of electron transfer (ET), highlighting the challenges of spectroscopic detection of CISS. However, the analysis allows the formulation of guidelines for the design of chiral organic model systems suitable to directly probe CISS-polarized ET.

2023 - Effect of Anesthesia Gases on the Oxygen Reduction Reaction [Articolo su rivista]
Gupta, Anu; Sang, Yutao; Fontanesi, Claudio; Turin, Luca; Naaman, Ron
abstract

: The oxygen reduction reaction (ORR) is of high importance, among others, because of its role in cellular respiration and in the operation of fuel cells. Recently, a possible relation between respiration and general anesthesia has been found. This work aims to explore whether anesthesia related gases affect the ORR. In ORR, oxygen which is in its triplet ground state is reduced to form products that are all in the singlet state. While this process is "in principle" forbidden because of spin conservation, it is known that if the electrons transferred in the ORR are spin-polarized, the reaction occurs efficiently. Here we show, in electrochemical experiments, that the efficiency of the oxygen reduction is reduced by the presence of general anesthetics in solution. We suggest that a spin-orbit coupling to the anesthetics depolarizes the spins. This causes both a reduction in reaction efficiency and a change in the reaction products. The findings may point to a possible relation between ORR efficiency and anesthetic action.

2023 - Growth Dynamics of Ultrathin Films of Benzo[1,2-b:4,5-b']dithiophene Derivatives on Au(111): A Photoelectron Spectroscopy Investigation [Articolo su rivista]
Stummo, Angelo; Montecchi, Monica; Parenti, Francesca; Vanossi, Davide; Fontanesi, Claudio; Capelli, Raffaella; Pasquali, Luca
abstract

: Ultrathin films of a stereoisomeric mixture of benzo[1,2-b:4,5-b']dithiophene derivatives were grown by thermal evaporation in vacuum on Au(111), and they were studied in situ by photoelectron spectroscopy. X-ray photons from a non-monochromatic Mg Kα conventional X-ray source and UV photons from a He I discharge lamp equipped with a linear polarizer were used. He I photoemission results were compared with density functional theory (DFT) calculations: density of states (DOS) and 3D molecular orbital density distribution. Au 4f, C 1s, O 1s, and S 2p core-level components suggest a surface rearrangement as a function of film nominal thickness, with the variation of the molecular orientation, from flat-laying at the initial deposition to tilted toward the surface normal at coverages exceeding 2 nm. Eventually, the DFT results were exploited in assigning of the valence band experimental structures. Moreover, polarization-dependent photoemission confirmed the tilted arrangement of the molecules, starting at 2 nm. A variation of the work function of 1.4 eV with respect to the clean substrate was measured, together with a valence band offset of 1.3 eV between the organic layer and gold.

2023 - Spin-dependent charge transmission through chiral 2T3N self-assembled monolayer on Au [Articolo su rivista]
Stefani, Andrea; Innocenti, Massimo; Giurlani, Walter; Calisi, Nicola; Pedio, Maddalena; Felici, Roberto; Favaretto, Laura; Melucci, Manuela; Zanardi, Chiara; Jones, Andrew C; Mishra, Suryakant; Zema, Nicola; Fontanesi, Claudio
abstract

: A gold surface is functionalized by chemisorption of the enantiopure N,N'-bis-[2,2';5',2″]tert-thiophene-5-yl methylcyclohexane-1,2-diamine (2T3N), a chiral oligothiophene derivative, via overnight incubation in a 2T3N ethanol solution. The Au|2T3N interface is characterized by x-ray photoelectron circular dichroism and comparing x-ray photoemission spectroscopy and electro-desorption results. Charge transmission at the Au|2T3N| solution interface is characterized by recording the cyclic voltammetry of the Fe(III)/Fe(II) reversible redox couple, finding a charge transfer rate constant, k°, variation from 1 × 10-1 to 3.3 × 10-2 cm s-1, when comparing the bare Au and the Au|2T3N interfaces, respectively. The "anomalous" high value of k° found for the chiral Au|2T3N interface can be rationalized on the basis of the chiral-induced spin selectivity effect, as further proved by magnetic-conductive atomic force microscopy measurements at room temperature. A spin polarization of about 30% is found.

2023 - Spin-dependent electrochemistry and electrochemical enantioselective recognition with chiral methylated bis(ethylenedithio)-tetrathiafulvalenes [Articolo su rivista]
Stefani, A.; Bogdan, A.; Pop, F.; Tassinari, F.; Pasquali, L.; Fontanesi, C.; Avarvari, N.
abstract

: Enantio-discrimination and spin-dependent electrochemistry (SDE), as a manifestation of the chirality-induced spin selectivity (CISS) effect, are important phenomena that can be probed by "chiral" electrochemistry. Here, we prepared chiralized surfaces of gold and nickel, to serve as working electrodes, through effective chemisorption of enantiopure dimethyl-bis(ethylenedithio)-tetrathiafulvalene (DM-BEDT-TTF) 1, tetramethyl-bis(ethylenedithio)-tetrathiafulvalene (TM-BEDT-TTF) 2, and their capped silver nanoparticle (AgNPs) aggregate by simple incubation of the metallic substrates. The effective chemisorption was checked by means of ultrahigh vacuum x-ray photoelectron spectroscopy (XPS) and by electro-desorption experiments, i.e., cyclic voltammetry (CV) scans showing a first electro-desorption peak at about -1.0 V. The Au|1 and Au|2 chiral electrodes were successfully used in CV experiments exploiting chiral redox probes. Finally, the hybrid interfaces Ni|enantiopure 1 or 2|AgNPs served as working electrodes in SDE experiments. In particular, the hybrid chiral interfaces Ni|(R)-2|AgNPs and Ni|(S)-2|AgNPs exhibited a significant spin-filtering ability, as a manifestation of the CISS effect, with average spin polarization values of 15%.

2022 - Charge transfer modulation in charge transfer co-crystals driven by crystal structure morphology [Articolo su rivista]
Solano, F.; Inaudi, P.; Abollino, O.; Giacomino, A.; Chiesa, M.; Salvadori, E.; Kociok-Kohn, G.; da Como, E.; Salzillo, T.; Fontanesi, C.
abstract

The electronic properties of a charge-transfer (donor-acceptor) semiconducting organic co-crystal, Perylene:F4-TCNQ (PE:F4) (the donor, D, is PE and the acceptor, A, is 2,3,5,6-tetrafluoro-7,7,8,8 tetracyanoquinodimethane (F4)) in its 3 : 2 stoichiometry, are experimentally and theoretically studied. This is performed by means of electron paramagnetic resonance (EPR) and solid state electrochemical techniques, such as cyclic voltammetry (CV) measurements on single crystals. In particular, solid state electrochemistry proves to be an effective tool to probe, on a macroscopic scale, the electronic characteristics of the co-crystal. However, EPR highlights the presence of spin ½ radicals localized on F4 molecules, possibly linked to defects. The experimental findings are discussed on the basis of density functional theory (DFT) based calculations, carried out using both the projector augmented wave (PAW), with “periodic boundary conditions” (pbc), method and the localized orbitals, molecular cluster, approach. In particular, a satisfying agreement is found between the experimental, 0.336 eV (electrochemical), and theoretical, 0.303 eV (PAW), band gaps. Differences with the reported optical bandgap are discussed considering excitonic effects.

2022 - Chirality enhances oxygen reduction [Articolo su rivista]
Sang, Y.; Tassinari, F.; Santra, K.; Zhang, W.; Fontanesi, C.; Bloom, B. P.; Waldeck, D. H.; Fransson, J.; Naaman, R.
abstract

Controlled reduction of oxygen is important for developing clean energy technologies, such as fuel cells, and is vital to the existence of aerobic organisms. The process starts with oxygen in a triplet ground state and ends with products that are all in singlet states. Hence, spin constraints in the oxygen reduction must be considered. Here, we show that the electron transfer efficiency from chiral electrodes to oxygen (oxygen reduction reaction) is enhanced over that from achiral electrodes. We demonstrate lower overpotentials and higher current densities for chiral catalysts versus achiral ones. This finding holds even for electrodes composed of heavy metals with large spin-orbit coupling. The effect results from the spin selectivity conferred on the electron current by the chiral assemblies, the chiral-induced spin selectivity effect.

2022 - Cyanide-free silver electrodeposition with polyethyleneimine and 5,5-dimethylhydantoin as organic additives for an environmentally friendly formulation [Articolo su rivista]
Pizzetti, F.; Salvietti, E.; Giurlani, W.; Emanuele, R.; Fontanesi, C.; Innocenti, M.
abstract

The influence of polyethyleneimine (PEI) as additive for cyanide-free silver bath, in combination with 5,5-dimethylhydantoin (DMH) as complexing agent, is studied. Cyclic voltammetry (CV) measurements are used to characterize the electrochemical behaviour of the Ag/DMH complex. The Ag electrodeposition from the cyanide-free silver-plating bath is analysed by CVs and the process is optimized varying the PEI concentration. Chronoamperometry is then used to investigate the electrodeposition mechanism, which is found to be a three-dimensional diffusion-controlled nucleation and growth mechanism, according to the Scharifker–Mostany's model. Smoother, brighter and blue coloured silver deposits are obtained in the presence of PEI in a Hull's cell test, at low density current. Eventually, the influence of nitrate anion is also investigated. The presence of nitrate increases the range of current density allowing for an effective Ag deposition.

2022 - Ethanol electro-oxidation reaction on the Pd(111) surface in alkaline media: insights from quantum and molecular mechanics [Articolo su rivista]
Campeggio, J.; Volkov, V.; Innocenti, M.; Giurlani, W.; Fontanesi, C.; Zerbetto, M.; Pagliai, M.; Lavacchi, A.; Chelli, R.
abstract

The ethanol electro-oxidation catalyzed by Pd in an alkaline environment involves several intermediate reaction steps promoted by the hydroxyl radical, OH. In this work, we report on the dynamical paths of the first step of this oxidation reaction, namely the hydrogen atom abstraction CH3CH2OH + OH → CH3CHOH + H2O, occurring at the Pd(111) surface and address the thermodynamic stability of the adsorbed reactants by means of quantum and molecular mechanics calculations, with special focus on the effect of the solvent. We have found that the impact of the solvent is significant for both ethanol and OH, contributing to a decrease in their adsorption free energies by a few dozen kcal mol−1 with respect to the adsorption energy under vacuum. Furthermore, we observe that hydrogen atom abstraction is enhanced for those simulation paths featuring large surface-reactant distances, namely, when the reactants weakly interact with the catalyst. The picture emerging from our study is therefore that of a catalyst whose coverage in an aqueous environment is largely dominated by OH with respect to ethanol. Nevertheless, only a small amount of them, specifically those weakly bound to the catalyst, is really active in the ethanol electro-oxidation reaction. These results open the idea of a rational design of co-catalysts based on the tuning of surface chemical properties to eventually enhance exchange current density.

2022 - Low-Cost Potentiometric Sensor for Chloride Measurement in Continuous Industrial Process Control [Articolo su rivista]
Vizza, M.; Marcantelli, P.; Giovani, C.; Giurlani, W.; Giusti, P.; Fontanesi, C.; Innocenti, M.
abstract

Recently, the new updates in legislation about drinking water control and human health have increased the demand for novel electrochemical low-cost sensors, such as potentiometric ones. Nowadays, the determination of chloride ion in aqueous solutions has attracted great attention in several fields, from industrial processes to drinking water control. Indeed, chloride plays a crucial role in corrosion, also influencing the final taste of beverages, especially coffee. The main goal is to obtain devices suitable for continuous and real-time analysis. For these reasons, we investigated the possibility to develop an easy, low-cost potentiometric chloride sensor, able to perform analysis in aqueous mediums for long immersion time and reducing the need of periodic calibration. We realized a chloride ion selective electrode made of Ag/AgCl sintered pellet and we tested its response in model solutions compatible with drinking water. The sensor was able to produce a stable, reproducible, and accurate quantification of chloride in 900 s, without the need for a preliminary calibration test. This opens the route to potential applications of this sensor in continuous, in situ, and real time measurement of chloride ions in industrial processes, with a reduced need for periodic maintenance.

2022 - Magnetic Field Effect on the Handedness of Electrodeposited Heusler Alloy [Articolo su rivista]
Giurlani, Walter; Vizza, Martina; Pizzetti, Federico; Bonechi, Marco; Savastano, Matteo; Sorace, Lorenzo; Stefani, Andrea; Fontanesi, Claudio; Innocenti, Massimo
abstract

Magneto-electrochemistry (MEC) experiments were carried out in the electrodeposition of a ferromagnetic Heusler alloy. The electrodeposition was carried out in the absence (as a reference) and in the presence of a magnetic field that was applied perpendicularly to the electrode–solution interface. The obtained metallic deposit was characterized by SEM-EDS, XRF, and XRD techniques. The ferromagnetic properties are assessed on the basis of SQUID measurements. The experimental results indicate that the influence of the presence of the magnetic field induces differences in the electrochemical measurements and a macroscopic handedness (chirality) in the deposit, which is a function of magnet orientation. Eventually, the coercivity of the Heusler alloy that was obtained in the presence of the magnetic field was larger compared to that of the deposit that was obtained without a magnetic field.

2022 - Molecular electrochemistry. An overview of a cross-field: Electrochemistry/spectroscopic/theoretical integrated approach [Articolo su rivista]
Salzillo, T.; Marchetti, A.; Vejpravova, J.; Fanjul Bolado, P.; Fontanesi, C.
abstract

This work summarizes state-of-the-art results achieved by combining, in a synergetic approach, the outcome obtained by electrochemical, spectroscopic and theoretical methods. A number of selected case-studies are reported, where such a synergetic approach enables to draw a complete picture of complex experimental systems. Finally, the relevance of the combined experimental and theoretical approach in solid-state electrochemistry, a territory amidst novel concepts in solid-state electronics, is recapped.

2022 - On the Dynamics of the Carbon–Bromine Bond Dissociation in the 1-Bromo-2-Methylnaphthalene Radical Anion [Articolo su rivista]
Bonechi, M.; Giurlani, W.; Innocenti, M.; Pasini, D.; Mishra, S.; Giovanardi, R.; Fontanesi, C.
abstract

This paper studies the mechanism of electrochemically induced carbon–bromine dissociation in 1-Br-2-methylnaphalene in the reduction regime. In particular, the bond dissociation of the relevant radical anion is disassembled at a molecular level, exploiting quantum mechanical calculations including steady-state, equilibrium and dissociation dynamics via dynamic reaction coordinate (DRC) calculations. DRC is a molecular-dynamic-based calculation relying on an ab initio potential surface. This is to achieve a detailed picture of the dissociation process in an elementary molecular detail. From a thermodynamic point of view, all the reaction paths examined are energetically feasible. The obtained results suggest that the carbon halogen bond dissociates following the first electron uptake follow a stepwise mechanism. Indeed, the formation of the bromide anion and an organic radical occurs. The latter reacts to form a binaphthalene intrinsically chiral dimer. This paper is respectfully dedicated to Professors Anny Jutand and Christian Amatore for their outstanding contribution in the field of electrochemical catalysis and electrosynthesis.

2022 - Optimisation of Thiourea Concentration in a Decorative Copper Plating Acid Bath Based on Methanesulfonic Electrolyte [Articolo su rivista]
Fabbri, L.; Giurlani, W.; Mencherini, G.; De Luca, A.; Passaponti, M.; Piciollo, E.; Fontanesi, C.; Caneschi, A.; Innocenti, M.
abstract

The role of thiourea as an organic additive in the nucleation and growth mechanism was studied for copper deposition and its application in the decorative electroplating and fashion accessory industries. The bath was designed to reduce the environmental and ecological impacts using methanesulfonic acid as electrolyte as an alternative to alkaline cyanide baths. We evaluated the nucleation and growth mechanism of copper exploiting voltametric and chronoamperometric measurements with a brightener concentration ranging from 0 to 90 ppm. We used the Scharifker– Hills model to estimate the type of nucleation mechanism after progressive addition of thiourea. Scanning electron microscope was employed for surface analysis and morphological characterisation of the nuclei. We verified that progressive nucleation is a key step in the obtainment of a shiny and homogeneous copper film, but an excess of thiourea could cause parasitic adsorption reactions on the surface of the substrate. X-ray fluorescence spectroscopy was used for the thickness determination of the copper deposits and the electrodeposition efficiency correlated to thiourea concentration. Finally, the optimal concentration of thiourea was assessed to be 60 ppm for the used formulation of copper plating.

2022 - PANI-Based Stacked Ferromagnetic Systems: Electrochemical Preparation and Characterization [Articolo su rivista]
Stefani, A; Fonollosa, Nt; Giurlani, W; Giovanardi, R; Fontanesi, C
abstract

In this work, the electropolymerization of polyaniline (PANI) is explored for its action as either a suitable coating or as a substrate for Nickel (Ni) and Magnetite (Fe3O4) surfaces. PANI electropolymerization has been achieved through cyclic voltammetry (CV), potentiostatic and galvanostatic electrochemical methods. The interaction between the obtained surfaces and the ferromagnetic layers (Ni and Fe3O4) has been investigated as a function of the pH of the electrolytic PANI solution, and also a variety of experimental parameters have been optimized in order to achieve the synthesis of PANI coatings (solvent, substrate, concentrations, and cell set-up). Thus, we obtained stable and consistent PANI thick films at the interface of both the nickel and the magnetite ferromagnetic materials.

2022 - Resorcinol electropolymerization process obtained via electrochemical oxidation [Articolo su rivista]
Bonechi, M.; Giurlani, W.; Stefani, A.; Marchetti, A.; Innocenti, M.; Fontanesi, C.
abstract

The electrochemical oxidation of resorcinol is experimentally studied on platinum, palladium and glassy carbon (GC) electrodes. The results of an exhaustive electrochemical characterization are presented, and integrated with the outcome of complementary chromatographic analytical techniques: LC-DAD and LC-MS. We demonstrate that upon electrochemical oxidation resorcinol polymerizes following an efficient and facile process, and once the electropolymerization is triggered a polymer film can be easily grown. The latter film features also good adhesion on the electrode surface.

2022 - The Importance of Electrical Impedance Spectroscopy and Equivalent Circuit Analysis on Nanoscale Molecular Electronic Devices [Articolo su rivista]
Jash, P.; Parashar, R. K.; Fontanesi, C.; Mondal, P. C.
abstract

To understand the electrical and charge transport phenomena in either single or large-scale molecular junctions, direct current (DC) measurements are mainly utilized. The current–voltage data obtained from DC measurements on molecular junctions (MJs) are employed to infer charge transport parameters, including barrier height, contact resistance, attenuation factor (β), and underlying transport mechanisms. However, DC measurements can not separate the individual electrical components, as it produces a total current that flows in the molecular junctions. Contact resistance obtained from the DC measurements by extrapolating plot of resistance versus chain length can not make exact value. In addition, defected SAMs-based MJs or junctions having a protective layer, DC measurements alone can predict neither proper electrical values nor the correct transport mechanisms and it lacks frequency response. Electrical impedance spectroscopy (EIS) along with the circuit model enables the identification of individual electrical components of the molecular junctions and faultless contact resistance values that facilitate the model of actual transport mechanisms. In this Review, the working principle of electrical impedance spectroscopy and circuit modeling to digitize the experimental results on various molecular junctions, is discussed. Overall, the EIS technique can serve as an excellent analytical tool for the proper electrical characterization that is highly desirable for molecular electronics.

2021 - A robust and cost-effective protocol to fabricate calibration standards for the thickness determination of metal coatings by XRF [Articolo su rivista]
Martinuzzi, S.; Giovani, C.; Giurlani, W.; Galvanetto, E.; Calisi, N.; Casale, M.; Fontanesi, C.; Ciattini, S.; Innocenti, M.
abstract

The XRF analysis is the most widespread in the industry setting to determine the thickness of metallic coatings, thanks to its ease of use, robustness, and non-destructive nature. However, accurate measurement requires primary standards that are expensive, not always available, and must be periodically replaced due to a limited shelf-life. In this context, we propose a versatile and cost-effective way for measuring the thickness of metallic coatings. Our method relies on a calibration curve based upon self-produced standards made through electroplating process and measured by a cross-sectional microscopy observation, either by SEM or light microscope. Thickness distribution was sufficiently homogeneous to be consistent with certified standard specifications: 5% of thickness variation in the central portion of the coatings (1 cm2) could be achieved for cathode length starting from 5 cm. Moreover, thickness distribution can be quantitatively predicted, relying only on primary current simulations, almost on simple shaped objects. The self-produced standard fit the calibration curve with a R2 > 0.999. Comparing different XRF quantitative methods with Student's t-test, we demonstrated that the proposed protocol is as effective as certified standards-based methods in terms of accuracy but at significantly lower costs.

2021 - Electrodeposition of Cu on PEDOT for a Hybrid Solid-State Electronic Device [Articolo su rivista]
Vizza, Martina; Pappaianni, Giulio; Giurlani, Walter; Stefani, Andrea; Giovanardi, Roberto; Innocenti, Massimo; Fontanesi, Claudio
abstract

Conductive polymers are nowadays attracting great attention for their peculiar mechanical, electrical and optical proprieties. In particular, PEDOT can be used in a wide range of innovative applications, from electroluminescent devices to photovoltaics. In this work, the electrochemical deposition of 3,4 ethylenedioxythiophene (EDOT) was performed on various substrates (ITO, thin films of gold and palladium on silicon wafers) by means of both potentiostatic and potentiodynamic techniques. This was intended to further expand the applications of electrochemically deposited PEDOT, particularly regarding the preparation of thin films in tight contact with electrode surfaces. This allows one to obtain systems prone to be used as electrodes in stacked devices. Chronoamperometric experiments were performed to study the nucleation and growth process of PEDOT. SEM, ESEM and AFM analysis allowed the characterization of the morphology of the polymeric films obtained. Raman and visible spectroscopy confirmed the high-quality of the coatings on the different substrates. Then, the PEDOT films were used as the base material for the further electrodeposition of a copper layer. In this way, a hybrid electronic device was obtained, by using electrochemical methods only. The high conductivity and ohmic behavior of the device were confirmed over a wide range of frequencies with electrical impedance spectroscopy analysis.

2021 - Exploiting the combination of displacement and chemical plating for a tailored electroless deposition of palladium films on copper [Articolo su rivista]
Fabbri, L.; Giurlani, W.; Biffoli, F.; Bellini, M.; Miller, H.; Fontanesi, C.; Vizza, F.; Innocenti, M.
abstract

Various formulations for electroless deposition, to obtain continuous nanometre-sized and micrometre-sized films of palladium on copper, were compared. We deposited ultrathin films using displacement plating formulations. We obtained continuous films with an equivalent thickness between 6 and 22 nm, measured by exploiting the K-ratio method with SEM-EDS of Pd layers. The Pd films obtained in this step of the work represent a cost-effective catalytic substrate. As a second step, we selected chemical plating as the procedure to obtain palladium films with a thickness in the micrometre range. An ammonia-based Pd chemical plating bath represent one of the most effective chemical plating formulations. To prevent copper substrates from being damaged by ammonia, displacement plating with palladium was also applied as a pre-treatment to make the use of these plating baths a viable way to obtain thicker palladium coatings. Palladium films showing good adherence, compact morphology, and a thickness over 1.5 µm were obtained, proving that the combination of two different electroless techniques was the key to develop a sustainable procedure for micrometre-sized palladium coatings, which could substitute electroplating of Pd in galvanic industry for decorative applications.

2021 - Influence of magnetic field on the electrodeposition and capacitive performances of MnO2 [Articolo su rivista]
Girimonte, A.; Stefani, A.; Innocenti, M.; Fontanesi, C.; Giovanardi, R.
abstract

This study focuses on the influence of an applied external magnetic field on the elec-trodeposition process and capacitive performances of MnO2, as pseudo-capacitive active material for supercapacitors electrodes. MnO2 was electrochemically deposited on Si/Au substrates in the presence and in the absence of a 0.5 T magnet, and its capacitive performance was tested via electrochemical characterization. The samples obtained in the presence of the magnetic field show a positive influence on the deposition process: the increase in deposition efficiency leads to more compact and uniform MnO2 coatings, with a decrease in capacitance values for the samples produced with the magnetic field.

2021 - On the Savéant's Concerted/Stepwise Model. The Electroreduction of Halogenated Naphthalene Derivatives as a Case Study [Articolo su rivista]
Stefani, Andrea; Giurlani, Walter; Bonechi, Marco; Marchetti, Andrea; Preda, Giovanni; Pasini, Dario; Innocenti, Massimo; Fontanesi, Claudio
abstract

The electroreduction of 1-Br-2-naphthol is shown to be a not-additive process with respect to the results obtained with two structurally related chiral [1,1′-Binaphthalene]-2,2′-diol, 6,6′-dibromo and 1,1′-Binaphthalene,6,6′-dibromo-2,2′-dimethoxy compounds. The 1-Br-2-naphtol reduction is accompanied by the carbon bromine dissociation, eventually producing a film due to a fast radical-radical cross reaction. The film formation is not observed in the BINOL-like chiral halogen-derivatives.

2021 - On the oxygen reduction reaction mechanism catalyzed by pd complexes on 2d carbon. A theoretical study [Articolo su rivista]
Bonechi, M.; Giurlani, W.; Vizza, M.; Savastano, M.; Stefani, A.; Bianchi, A.; Fontanesi, C.; Innocenti, M.
abstract

Oxygen Reduction Reaction (ORR) is the bottle-neck strategic reaction ruling the fuel cell efficiency process. The slow kinetics of the reaction require highly effective electrocatalysts for proper boosting. In this field, composite catalysts formed by carbon nanotubes functionalized with palladium(II) complexes showed surprising catalytic activity comparable to those of a commercial Pt electrode, but the catalytic mechanisms of these materials still remain open to discussion. In this paper, we propose the combination of experimental and theoretical results to unfold the elementary reaction steps underlying the ORR catalysis.

2021 - Spin Multiplicity and Solid-State Electrochemical Behavior in Charge-Transfer Co-crystals of DBTTF/F4TCNQ [Articolo su rivista]
Solano, F.; Inaudi, P.; Chiesa, M.; Kociok-Kohn, G.; Salvadori, E.; Da Como, E.; Vanossi, D.; Malandrino, M.; Carmieli, R.; Giacomino, A.; Fontanesi, C.
abstract

Charge-transfer crystals exhibit unique electronic and magnetic properties with interesting applications. The charge-transfer single crystal formed by dibenzotetrathiafulvalene (DBTTF) together with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) presents a long-range ordered supramolecular structure of segregated stacks, with a unitary degree of charge transfer. Thus, the crystal structure is composed of dimerized radical molecules with unpaired electrons. The energy levels and the spin degrees of freedom of this material were investigated by solid-state electrochemistry and electron paramagnetic resonance (EPR) spectroscopy. The electrochemical data, supported by density functional theory calculations, show how this organic Mott insulator has an electronic gap in the range of hundreds of meV. EPR experiments show the presence of a ground-state S = 1 triplet spin state along with localized S = 1/2 spins. The calculations also predict a ground-state triplet configuration, with the singlet configuration at 170 meV higher energy. DBTTF/F4TCNQ seems to be a candidate material for organic electronic and spintronic applications.

2021 - Spin control using chiral templated nickel [Articolo su rivista]
Mishra, Suryakant; Pasquali, Luca; Fontanesi, Claudio
abstract

This Letter reports an original spin valve device that is based on a chiral templated nickel material. Chirality in Ni is induced by exploiting co-electrodeposition of an organic chiral template. In this specific case, the chiral templating is enantiopure tartaric acid (TA). Facile electrodeposition (co-deposition) in ambient conditions produces a nickel chiral-templated material. Z-shaped magnetoresistance curves, switching sign as a function of TA handedness, prove the peculiar ferromagnetic character induced by the presence of a chiral compound. Synchrotron measurements using circular polarized light, x-ray natural circular dichroism, confirm the chirality of the Ni in the TA/Ni composite. Density functional theory calculation proves the existence of a strong electronic delocalization involving the tartaric acid and Ni. The significant finding of this Letter is that chiral templated Ni paves the way for future spin valve, which will be able to control the spin without an external magnetic field (as indeed foreseen within the chiral induced spin selectivity-effect framework).

2021 - The Fundamental and Underrated Role of the Base Electrolyte in the Polymerization Mechanism. The Resorcinol Case Study [Articolo su rivista]
Bonechi, M.; Innocenti, M.; Vanossi, D.; Fontanesi, C.
abstract

The Kane-Maguire polymerization mechanism is disassembled at a molecular level by using DFT-based quantum mechanical calculations. Resorcinol electropolymerization is selected as a case study. Stationary points (transition states and intermediate species) leading to the formation of the dimer are found on the potential energy surface (PES), and elementary reactions involved in the dimer formation are characterized. The latter allow to further propagate the polymerization chain reaction, when applied recursively. In this paper, the fundamental role of the sulfate anion (a typical base electrolyte) is addressed. Investigation of the PES in terms of both stationary-state properties and of ab initio molecular dynamics results (dynamic reaction coordinate) allows the appreciation in detail of the critical role of the base electrolyte anion in making the proton dissociation from the initial radical ion, a feasible (downhill in energy) process.

2021 - Wavy graphene sheets from electrochemical sewing of corannulene [Articolo su rivista]
Bruno, Carlo; Ussano, Eleonora; Barucca, Gianni; Vanossi, Davide; Valenti, Giovanni; Jackson, Edward A.; Goldoni, Andrea; Litti, Lucio; Fermani, Simona; Pasquali, Luca; Meneghetti, Moreno; Fontanesi, Claudio; Scott, Lawrence T.; Paolucci, Francesco; Marcaccio, Massimo
abstract

The presence of non-hexagonal rings in the honeycomb carbon arrangement of graphene produces rippled graphene layers with valuable chemical and physical properties. In principle, a bottom-up approach to introducing distortion from planarity of a graphene sheet can be achieved by careful insertion of curved polyaromatic hydrocarbons during the growth of the lattice. Corannulene, the archetype of such non-planar polyaromatic hydrocarbons, can act as an ideal wrinkling motif in 2D carbon nanostructures. Herein we report an electrochemical bottom-up method to obtain egg-box shaped nanographene structures through a polycondensation of corannulene that produces a new conducting layered material. Characterization of this new polymeric material by electrochemistry, spectroscopy, electron microscopy (SEM and TEM), scanning probe microscopy, and laser desorption-ionization time of flight mass spectrometry provides strong evidence that the anodic polymerization of corannulene, combined with electrochemically induced oxidative cyclodehydrogenations (Scholl reactions), leads to polycorannulene with a wavy graphene-like structure.

2020 - Asymmetric reactions induced by electron spin polarization [Articolo su rivista]
Bloom, B. P.; Lu, Y.; Metzger, T.; Yochelis, S.; Paltiel, Y.; Fontanesi, C.; Mishra, S.; Tassinari, F.; Naaman, R.; Waldeck, D. H.
abstract

Essential aspects of the chiral induced spin selectivity (CISS) effect and their implications for spin-controlled chemistry and asymmetric electrochemical reactions are described. The generation of oxygen through electrolysis is discussed as an example in which chirality-based spin-filtering and spin selection rules can be used to improve the reaction's efficiency and selectivity. Next the discussion shifts to illustrate how the spin selectivity of chiral molecules (CISS properties) allows one to use the electron spin as a chiral bias for inducing asymmetric reactions and promoting enantiospecific processes. Two enantioselective electrochemical reactions that have used polarized electron spins as a chiral reagent are described; enantioselective electroreduction to resolve an enantiomer from a racemic mixture and an oxidative electropolymerization to generate a chiral polymer from achiral monomers. A complementary approach that has used spin-polarized, but otherwise achiral, molecular films to enantiospecifically associate with one enantiomer from a racemic mixture is also discussed. Each of these reaction types use magnetized films to generate the spin polarized electrons and the enantiospecificity can be selected by choice of the magnetization direction, North pole versus South pole. Possible paths for future research in this area and its compatibility with existing methods based on chiral electrodes are discussed.

2020 - Exchange Interactions Drive Supramolecular Chiral Induction in Polyaniline [Articolo su rivista]
Mishra, S.; Kumar, A.; Venkatesan, M.; Pigani, L.; Pasquali, L.; Fontanesi, C.
abstract

The focus of this paper is on the intermolecular interaction active between polyaniline (PANI) and 10-camphorsulfonic acid (10CSA). Enantiopure 10CSA, present in the electropolymerization solution, promotes chiral induction in the supramolecular polyaniline polymer (cPANI). Tight integration of experimental data (circular dichroism, CD, near edge X-ray absorption spectra, NEXAFS, conductive probe atomic force microscopy, CP-AFM) and theoretical [density functional theory, (DFT)] results allows to unfold the nature of the electronic interaction between PANI and 10CSA and to shed light on the physical interactions inducing the chiral character to bulk pristine non-chiral PANI: eventually yielding cPANI. The electropolymerization follows a “wet chemistry” method: electrochemical polymerization of aniline in the co-presence in bulk solution of enantiopure 10-camphorsulfonic acid (10CSA). The latter is exploited as chirality inductor. The method of integration between experimental results with ab-initio theoretical calculations, strongly suggests that the chiral induction exerted by the CSA stems from exchange interaction between CSA and PANI.

2020 - Influence of Chiral Compounds on the Oxygen Evolution Reaction (OER) in the Water Splitting Process [Articolo su rivista]
Gazzotti, M.; Stefani, A.; Bonechi, M.; Giurlani, W.; Innocenti, M.; Fontanesi, C.
abstract

Results are presented concerning the influence on the water splitting process of enantiopure tartaric acid present in bulk solution. Stainless steel and electrodeposited nickel are used as working electrode (WE) surface. The latter is obtained by electrodeposition on the two poles of a magnet. The influence and role played by the chiral compound in solution has been assessed by comparing the current values, in cyclic voltammetry (CV) experiments, recorded in the potential range at which oxygen evolution reaction (OER) occurs. In the case of tartaric acid and nickel WE a spin polarization of about 4% is found. The use of the chiral environment (bulk solution) and ferromagnetic chiral Ni electrode allows for observing the OER at a more favorable potential: About 50 mV (i.e., a cathodic, less positive, shift of the potential at which the oxygen evolution is observed).

2020 - Modelling of the Elementary Steps Involved in the Aluminum Electrochemical Deposition from Ionic Liquid Based Solution: The BMImCl/AlCl3 System [Articolo su rivista]
Innocenti, M; Giaccherini, A; Chelli, R; Martinuzzi, S; Giurlani, W; Passaponti, M; Lavacchi, A; Fontanesi, C
abstract

The energy hierarchy, of the main chemical species involved in the reaction mechanism relevant to the electrodeposition of aluminum in 1-Butyl-3-methylimidazolium chloride/aluminum trichloride solution (BMImCl/AlCl3), is studied by using ab-initio based theoretical calculations. Eventually, a reasonable theoretical estimate of energies, involved in the principal reactions ruling the aluminum electrodeposition from BMImCl ionic liquid solutions, is obtained. For screening purposes (geometry optimization and Hessian calculations) the CAMB3LYP density functional, DFT, has been used. Then single point (exploiting CAMB3LYP optimized geometries) energy data are obtained at the Moller-Plesset (MP2) level of the theory. They are used to cross-check DFT results. A reaction mechanism emerges in which, although the species AlCl4- is formed with very high efficiency from the neutral species AlCl3, the competing reaction AlCl4- + AlCl3 (sic) Al2Cl7- points to an almost complete conversion of aluminum to the dimeric form into bulk solution. This is observed in the absence and, most importantly, in the presence of a coordinating BMIm(+) cation. In this respect, the presence of BMIm(+) does not seem to affect significantly the equilibrium between the monomeric and dimeric forms of aluminum. This outcome is very interesting because the dimeric species is directly reduced to yield the metal aluminum. Indeed, a larger concentration of Al2Cl7- gives due reason for a more effective electrodeposition process, as it is experimentally observed in the ionic liquid medium. (C) The Author(s) 2019. Published by ECS.

2020 - Optimisation Study of Co Deposition on Chars from MAP of Waste Tyres as Green Electrodes in ORR for Alkaline Fuel Cells [Articolo su rivista]
Passaponti, M.; Lari, L.; Bonechi, M.; Bruni, F.; Giurlani, W.; Sciortino, G.; Rosi, L.; Fabbri, L.; Vizza, M.; Lazarov, V. K.; Fontanesi, C.; Innocenti, M.
abstract

Oxygen Reduction Reaction (ORR) catalysts, from waste automobile tyres obtained from Microwave assisted pyrolysis (MAP), were enriched with Co and Cu using the simple treatments sonochemical and electrochemical deposition. Catalytic activity was evaluated through onset potential and number of exchanged electrons measurements. Electrochemical data demonstrate an improvement in catalytic activity of the electrochemical modified char with Co. Char electrodes enriched with Co show a maximum positive shift of 40 mV with respect to raw char electrodes with a number of exchanged electrons per O2 molecule close to 4 (as for Pt) for the best sample. This corresponds to a reduction of the production of unwanted oxygen peroxide from 23% for raw char to 1%. Sample structure evolution before and after electrochemical deposition and electro-catalysis was investigated by scanning transmission electron microscopy and XPS. Such electrochemical treatments open new possibilities of refining waste chars and finding an economic alternative to noble metals-based catalysts for alkaline fuel cells.

2020 - Spin dependent electrochemistry: Focus on chiral vs achiral charge transmission through 2D SAMs adsorbed on gold [Articolo su rivista]
Innocenti, Massimo; Passaponti, Maurizio; Giurlani, Walter; Giacomino, Agnese; Pasquali, Luca; Giovanardi, Roberto; Fontanesi, Claudio
abstract

The efficiency of charge transmission in chiral compared to achiral molecular systems, of structurally related compounds, is probed via cyclic voltammetry measurements. For such a purpose five different thiols have been selected two achiral (i.e. 3-mercaptopropionic acid (MPA) and 8-mercapto-1-octanol (M8O)) and three chiral (i.e. L- and D-cysteine (Lcys, Dcys) and D-penicillamine (Dpen)). These compounds are used to form 2D self-assembled monolayers (SAM) on gold. Cyclic voltammetry (CV) measurements, by using the potassium hexacyanoferrate(III)/potassium hexacyanoferrate(II) redox couple (Fe3Fe2), are exploited to probe the charge transfer ability of the electrode|SAM|solution interface. In particular, MPA, Lcys and Dpen compounds are se- lected due to their quite similar structural and geometrical characteristics (virtually the same molecular length and terminal groups). M8O is a longer SAM forming thiol, which was selected as a reference blocking electrode compound. The comparison of the cyclic voltammetry data shows that a better ability in the charge transmission is obtained when chiral SAM are used; namely in the case of L-cysteine and D-penicillamine. This result can be related to the spin filtering ability of chiral compounds: chiral induced spin selectivity (CISS) effect. As rational- ized on the basis of theoretical values of optical rotation (OR), calculated at the CAMB3LYP/6-31G(d,p) level of the theory.

2020 - The electron spin as a chiral reagent [Articolo su rivista]
Naaman, Ron; Metzger, Tzuriel S; Mishra, Suryakant; Bloom, Brian P; Goren, Naama; Neubauer, Avner; Shmul, Guy; Wei, Jimeng; Yochelis, Shira; Tassinari, Francesco; Fontanesi, Claudio; Waldeck, David H; Paltiel, Yossi
abstract

In contrast to the notion that enantiospecific chemical reactions require a chiral reagent molecule or catalyst, this work shows that enantioselective chemical transformations can be induced by the electron spin itself. As electrons are injected from a magnetized electrode into an adsorbed molecule, they have a distinct spin orientation relative to their velocity; i.e., they have a well-defined helicity. Thus, it is possible to replace a conventional enantiopure chemical reagent by spin-polarized electrons that provide the chiral bias for enantioselective reactions. Three examples of enantioselective chemistry, resulting from electron spin polarization, are presented. The first example demonstrates enantioselective association of a chiral molecule with an achiral self-assembled monolayer film that is spin-polarized. The other two studies show that the chiral bias provided by the electron helicity can drive both reduction and oxidation enantiospecific electrochemical reactions. In each case, the enantioselectivity does not result from enantiospecific interaction of the molecule with the ferromagnetic electrode, but rather it arises from the polarized spin that crosses the interface between the substrate and the molecule. In all three cases, the direction of the electron spin polarization defines the sense (left-handed versus right-handed) of the enantioselectivity. This work demonstrates a new mechanism for realizing enantioselective chemistry.

2020 - Underpotential‐Assisted Electrodeposition of Highly Crystalline and Smooth Thin Film of Bismuth [Articolo su rivista]
Giurlani, Walter; Cavallini, Massimiliano; Picca, Rosaria Anna; Cioffi, Nicola; Passaponti, Maurizio; Fontanesi, Claudio; Lavacchi, Alessandro; Innocenti, Massimo
abstract

2019 - A SYSTEM AND METHOD FOR PROMOTING CHEMICAL REACTIONS [Brevetto]
Naaman, Ron; Fontanesi, Claudio; Tassinari, Francesco; Mishra, Suryakant; Capua, Eyal; Paltiel, Yossef; Yochelis, Shira; Metzger, Tzuriel
abstract

A system and method for use in synthesis and promoting interactions of chiral molecules. The system comprising: a container configured for containing fluid mixture comprising one or more reactant molecules, and at least one surface comprising ferromagnetic or paramagnetic material, located to be in at least partial contact with reactants in said container. The ferromagnetic of paramagnetic material is magnetized with magnetization direction perpendicular to said at least one surface, thereby providing chiral selective synthesis from said one or more reactant molecules. The technique enables selective interactions of enantiomers of selected handedness of chiral molecules or formation of selected enantiomers from achiral molecule reactants.

2019 - Chirality and its role in the electronic properties of peptides: spin filtering and spin polarization [Articolo su rivista]
Naaman, R.; Fontanesi, C.; Waldeck, D. H.
abstract

Abstract non presente

2019 - Combined effect of organic-inorganic heterostructure to enhance electrochemical capacitance [Articolo su rivista]
Mishra, Suryakant; Fontanesi, Claudio
abstract

An original hybrid, organic/inorganic, composite material with a unique shape nanostructures (NSs) are prepared and characterized. Nanopetals of nickel oxide (NiO-NPs) substrate is used to grow polyaniline (PANI) via electrochemical polymerization, allowing to obtain a quite peculiar nanohemispheres morphology (PANI-NHs). A unique combination of different hydrothermal and electrochemical techniques are used to grow these complex architectures at nanoscale. Electron microscopies (SEM and TEM) are used for the morphology analysis. XPS, PMIRRAS and Raman measurements were used for surface characterization. Along the experimental study, IR spectra are calculated for oligomers of leucoemeraldine and pernigraniline. By the present combination of chemical and physical characteristics at the nanoscale, the overall surface area of our hybrid composite material is greatly increased, thus enhancing the electrochemical activity of the single constituent's composition. Note that, the specific capacitance of the present NiO-NPs/PANI-NHs composite material is ~545F/g, which is higher than that of the individual starting materials. Thus, a dramatic improvement is obtained in the performance of energy storage with respect to the parental materials, as a nanoscale effect.

2019 - Effect of Oxidative Damage on Charge and Spin Transport in DNA [Articolo su rivista]
Mishra, S.; Poonia, V. S.; Fontanesi, C.; Naaman, R.; Fleming, A. M.; Burrows, C. J.
abstract

A Hall device was used for measuring spin polarization on electrons that are either reorganized within the molecules or transmitted through the self-assembled monolayers of DNA adsorbed on the device surface. We were able to observe spin-dependent charge polarization and charge transport through double-stranded DNA of various lengths and through double-stranded DNA containing oxidative damage. We found enhancement in the spin-dependent transport through oxidatively damaged DNA. This phenomenon can be rationalized either by assuming that the damaged DNA is characterized by a higher barrier for conduction or by charge transfer through the DNA being conducted through at least two channels, one involves the bases and is highly conductive but less spin selective, while the other pathway is mainly through the ribophosphate backbone and it is the minor one in terms of charge transmission efficiency, but it is highly spin selective.

2019 - Enantioseparation by crystallization using magnetic substrates [Articolo su rivista]
Tassinari, F.; Steidel, J.; Paltiel, S.; Fontanesi, C.; Lahav, M.; Paltiel, Y.; Naaman, R.
abstract

Enantiospecific crystallization of the three amino acids asparagine (Asn), glutamic acid hydrochloride (Glu·HCl) and threonine (Thr), induced by ferromagnetic (FM) substrates, is reported. The FM substrates were prepared by evaporating nickel capped with a thin gold layer on standard silicon wafers. Magnets were positioned underneath the substrate with either their North (N) or South (S) poles pointing up. Asymmetric induction, controlled by the magnetic substrates, was demonstrated for the crystallization of the pure enantiomers and was then extended for the racemic mixtures of Asn and Glu·HCl. In the case of the solution of the pure enantiomers, the l enantiomer was crystallized preferentially at one pole of the magnet and the d enantiomer at the other. Consequently, the racemates of Asn and Glu·HCl undergo separation under the influence of the magnetic substrate. With Thr, however, despite the enantiospecific interactions of the pure enantiomers with the FM, no separation of the emerging crystals could be achieved with the racemates, although they crystallize as conglomerates, implying differences taking place in the crystallization step. The results reported here are not directly related to the magnetic field, but rather to the aligned spins within the ferromagnets. The findings provide a novel method for resolving enantiomers by crystallization and offer a new perspective for a possible role played by magnetic substrates regarding the origin of chirality in nature.

2019 - Highlighting spin selectivity properties of chiral electrode surfaces from redox potential modulation of an achiral probe under an applied magnetic field [Articolo su rivista]
Benincori, T.; Arnaboldi, S.; Magni, M.; Grecchi, S.; Cirilli, R.; Fontanesi, C.; Mussini, P. R.
abstract

Impressive spin-related effects are observed in cyclic voltammetry (CV) experiments performed under an applied magnetic field on a non-ferromagnetic electrode modified with a thin electroactive oligothiophene film, either “inherently chiral” or featuring chiral pendants with stereogenic centres. When flipping the magnet's north/south orientation, the CV peaks of two achiral, chemically reversible Fe(iii)/Fe(ii) redox couples in aqueous or organic solution undergo impressive potential shifts (up to nearly 0.5 V depending on protocol conditions), specularly by changing the film's (R)- or (S)-configuration. The magnitude of the potential shift decreases upon increasing both the polymer film thickness and the distance between the permanent magnet and the electrode surface. Such unprecedented spin-related redox potential modulation, obtained in the absence of a magnetic electrode acting as a spin injector, provides striking evidence (as well as an attractive evaluation criterion) of the spin selectivity properties of chiral thin films.

2019 - Quantitative resonant soft x-ray reflectivity from an organic semiconductor single crystal [Articolo su rivista]
Capelli, R.; Da Como, E.; Kociok-Köhn, G.; Fontanesi, C.; Verna, A.; Pasquali, L.
abstract

Resonant soft X-ray reflectivity at the carbon K-edge was applied to a trigonal tetracene single crystal. The angular resolved reflectivity was quantitatively simulated describing the tetracene crystal in terms of its dielectric tensor, which was derived from the anisotropic absorption cross section of the single molecule, as calculated by density functional theory. A good agreement was found between the experimental and theoretically predicted reflectivity. This allows us to assess the anisotropic optical constants of the organic material, probed at the carbon K-edge, in relation to the bulk/surface structural and electronic properties of the crystal, through empty energy levels.

2019 - Redox-Active Ferrocene grafted on H-Terminated Si(111): Electrochemical Characterization of the Charge Transport Mechanism and Dynamics [Articolo su rivista]
Fontanesi, C.; Como, E. D.; Vanossi, D.; Montecchi, M.; Cannio, M.; Mondal, P. C.; Giurlani, W.; Innocenti, M.; Pasquali, L.
abstract

Electroactive self-assembled monolayers (SAMs) bearing a ferrocene (Fc) redox couple were chemically assembled on H-terminated semiconducting degenerate-doped n-type Si(111) substrate. This allows to create a Si(111)|organic-spacer|Fc hybrid interface, where the ferrocene moiety is covalently immobilized on the silicon, via two alkyl molecular spacers of different length. Organic monolayer formation was probed by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) and X-ray photoelectron spectroscopy (XPS) measurements, which were also used to estimate thickness and surface assembled monolayer (SAM) surface coverage. Atomic force microscopy (AFM) measurements allowed to ascertain surface morphology and roughness. The single electron transfer process, between the ferrocene redox probe and the Si electrode surface, was probed by cyclic voltammetry (CV) measurements. CVs recorded at different scan rates, in the 10 to 500 mV s−1 range, allowed to determine peak-to-peak separation, half-wave potential, and charge-transfer rate constant (KET). The experimental findings suggest that the electron transfer is a one electron quasi-reversible process. The present demonstration of surface engineering of functional redox-active organometallic molecule can be efficient in the field of molecular electronics, surface-base redox chemistry, opto-electronic applications.

2019 - Synthesis and Characterization of Semiconductor Polymer Doped with FeCl3 and I2 [Articolo su rivista]
Bouabdallah, Daho; Fontanesi, C.; Messori, M.; Dehbi, A.; Belfedal, A.
abstract

Abstract: The conductive polymer-based applications combine low cost, simple manufacturing procedure, flexibility and other properties. However, the low viscosity and solubility of these polymers make it difficult to produce layers by using industrial techniques. Among the most commonly used conjugated conductive organic polymers we can mention polyacetylene, polythiophene, polypyrrole, polyaniline, etc. In order to test them in further applications, new copolymers of thiophene and p-methoxybenzaldehyde were synthesized. The copolymers obtained will be characterized by several techniques (NMR, UV, CV, ATG, and electrical characterization). The study of the optical properties after doping is performed according to oxidation-reduction reactions by FeCl3, I2, in order to apprehend the redox behavior of this copolymer. The calculated value of energy gap Egcv of the studied polymers shows a decrease with the oxidation agent doping according to their oxidation potential, from 2.48 eV for the no doped copolymer passing by 2.22 eV for the copolymer doped with I2 and up to 1.5 eV for the copolymer doped with FeCl3. The decrease of the energy gap with the doping (FeCl3 and I2) corresponds to the increase of the conductivity with doping from 2.85 × 10–5 S m–1 for no doped polymer to 7.86 × 10–5 S m–1 for copolymer doped with I2 and 1.55 × 10–4 S m–1 for copolymer doped with FeCl3.

2018 - Chiral Magneto-Electrochemistry [Articolo su rivista]
Kumar, Anup; Mondal, Prakash; Fontanesi, Claudio
abstract

Magneto-electrochemistry (MEC) is a unique paradigm in science, where electrochemical experiments are carried out as a function of an applied magnetic field, creating a new horizon of potential scientific interest and technological applications. Over time, detailed understanding of this research domain was developed to identify and rationalize the possible effects exerted by a magnetic field on the various microscopic processes occurring in an electrochemical system. Notably, until a few years ago, the role of spin was not taken into account in the field of magneto-electrochemistry. Remarkably, recent experimental studies reveal that electron transmission through chiral molecules is spin selective and this effect has been referred to as the chiral-induced spin selectivity (CISS) effect. Spin-dependent electrochemistry originates from the implementation of the CISS effect in electrochemistry, where the magnetic field is used to obtain spin-polarized currents (using ferromagnetic electrodes) or, conversely, a magnetic field is obtained as the result of spin accumulation.

2018 - Chiro-Spintronics: Spin-Dependent Electrochemistry and Water Splitting Using Chiral Molecular Films [Articolo su rivista]
Mondal, Prakash Chandra; Mtangi, Wilbert; Fontanesi, Claudio
abstract

Molecular spintronics or spin‐based electronics, which utilizes both the spin degrees of freedom and electron charge, has become a hot topic in modern science. Since the introduction of spintronics in 1988, many efforts have been devoted to controlling spin‐polarized current using an external magnetic field, leading to the implementation of commercial solid‐state devices based on the giant magnetoresistance effect. In molecular spintronics, much progress has been achieved with organic molecules, but the role played by chiral molecules is yet to be explored in detail, while it promises to play a role in the future. It has been proved that the interaction of electrons with chiral molecules is spin specific, as supported by several experimental tools, and by theoretical studies. This effect is named “chiral‐induced spin selectivity” (CISS). CISS is based on the fact that chiral molecules exhibit spin‐specific transport properties, and hence can be used as a substitute for ferromagnetic materials. Here, recent spin‐dependent electrochemistry results are highlighted, where chiral molecules are immobilized on a ferromagnetic electrode. Practical applications of the CISS effect, for spin control of charge transport in complex molecular architectures, and in the water‐splitting process are also reviewed.

2018 - Electrochemistry of Metalloproteins Attached through Functional Self-Assembled Monolayers on Gold and Ferromagnetic Electrodes [Articolo su rivista]
Mondal, Prakash Chandra; Fontanesi, Claudio
abstract

We report the experimental results of a study of the electron-transfer processes of redox-active metalloproteins bound to mixed self-assembled monolayers (SAMs) on magnetic (nickel or ultrathin gold-coated nickel) or nonmagnetic (gold) electrodes. Metalloproteins, such as hemoglobin (Hb), CytochromeC (CytC), and CytC oxidase, are attached through electrostatic interactions to the free carboxylate or imidazole groups present in the mixed SAMs. The formation of both mixed SAMs and SAM/metalloprotein heterostructures were confirmed by using advanced surface analysis techniques, such as polarization modulation infrared reflection absorption spectroscopy and aqueous contact angle measurements. Electrochemical measurements indicated a stronger electronic coupling between Hb and CytC oxidase and the mixed-SAM-coated gold or gold-coated-nickel electrodes, whereas a weaker coupling was found between the protein and the pure nickel electrode. Surface coverage and the electron-transfer rate constant were estimated from the cyclic voltammetry data.

2018 - Injection of Spin-Polarized Electrons into a AlGaN/GaN Device from an Electrochemical Cell: Evidence for an Extremely Long Spin Lifetime [Articolo su rivista]
Kumar, A.; Capua, E.; Fontanesi, C.; Carmieli, R.; Naaman, R.
abstract

Spin-polarized electrons are injected from an electrochemical cell through a chiral self-assembled organic monolayer into a AlGaN/GaN device in which a shallow two-dimensional electron gas (2DEG) layer is formed. The injection is monitored by a microwave signal that indicates a coherent spin lifetime that exceeds 10 ms at room temperature. The signal was found to be magnetic field independent; however, it depends on the current of the injected electrons, on the length of the chiral molecules, and on the existence of 2DEG.

2018 - Spin-Dependent Processes Measured without a Permanent Magnet [Articolo su rivista]
Fontanesi, C.; Capua, E.; Paltiel, Y.; Waldeck, D. H.; Naaman, R.
abstract

A novel Hall circuit design that can be incorporated into a working electrode, which is used to probe spin-selective charge transfer and charge displacement processes, is reviewed herein. The general design of a Hall circuit based on a semiconductor heterostructure, which forms a shallow 2D electron gas and is used as an electrode, is described. Three different types of spin-selective processes have been studied with this device in the past: i) photoinduced charge exchange between quantum dots and the working electrode through chiral molecules is associated with spin polarization that creates a local magnetization and generates a Hall voltage; ii) charge polarization of chiral molecules by an applied voltage is accompanied by a spin polarization that generates a Hall voltage; and iii) cyclic voltammetry (current–voltage) measurements of electrochemical redox reactions that can be spin-analyzed by the Hall circuit to provide a third dimension (spin) in addition to the well-known current and voltage dimensions. The three studies reviewed open new doors into understanding both the spin current and the charge current in electronic materials and electrochemical processes.

2018 - Spin-controlled electrochemistry using chiral electrodes: Effects on water electrolysis [Abstract in Atti di Convegno]
Tassinari, F; Mtangi, W; Banerjee-Ghosh, K; Adelizzi, B; Parenti, F; Vankayala, K; Palmans, A; Jentzsch, Av; Fontanesi, C; Mucci, A; Meijer, E; Naaman, R
abstract

Hydrogen is the ecologically ideal energy vector. Efficient photo-electrochemical production of hydrogen from water could be the optimal solution to the energy storage problems related to renewable sources. However, in the water splitting reaction the electric potential required to initiate the process significantly exceeds the thermodynamic limit. By controlling the spins of the electrons that are transferred from the solution to the anode, and ensuring that they are coaligned, the threshold voltage for the process can in theory be decreased to that of the thermodynamic voltage. In the present study, by using TiO2 anodes coated with chiral materials, we explore what are the effects of having a spin-polarized current on water electrolysis. The spin-polarization arises from exploiting what is known as Chiral Induced Spin Selectivity effect by using chiral molecules as spin filters. When using chiral molecules instead of a non-chiral analogue, the hydrogen production from water is enhanced, the threshold voltage is reduced and the by-product formation of hydrogen peroxide is suppressed.

2018 - Spin-controlled electrochemistry using chiral electrodes: Effects on water electrolysis [Poster]
Tassinari, F.; Mtangi, W.; Banerjee-Ghosh, K.; Adelizzi, B.; Parenti, F.; Vankayala, K.; Palmans, A.; Jentzsch, A. V.; Fontanesi, C.; Mucci, A.; Meijer, E. W.; Naaman, R
abstract

Hydrogen is the ecologically ideal energy vector. Efficient photo-electrochemical production of hydrogen from water could be the optimal solution to the energy storage problems related to renewable sources. However, in the water splitting reaction the electric potential required to initiate the process significantly exceeds the thermodynamic limit. By controlling the spins of the electrons that are transferred from the solution to the anode, and ensuring that they are coaligned, the threshold voltage for the process can in theory be decreased to that of the thermodynamic voltage. In the present study, by using TiO2 anodes coated with chiral materials, we explore what are the effects of having a spin-polarized current on water electrolysis. The spin-polarization arises from exploiting what is known as Chiral Induced Spin Selectivity effect by using chiral molecules as spin filters. When using chiral molecules instead of a non-chiral analogue, the hydrogen production from water is enhanced, the threshold voltage is reduced and the by-product formation of hydrogen peroxide is suppressed. Figure: control of hydrogen peroxide production. UV-vis spectra from the titration of the used electrolyte (Na2SO4) with o-tolidine of bare TiO2 and TiO2 electrodes coated with (A) self-assembled Zn-porphyrins of either achiral (A-Zn) or chiral (S-Zn) and (B) TPyA molecules. (C) When the electrons transfer to the anodes is non spin specific the spins of the unpaired electrons on the two radicals are aligned antiparallel, hence the interaction is on a singlet surface that correlates with the production of hydrogen peroxide (H2O2). (D) When the electron transfer to the anode is spin specific, the spins of the two electrons are aligned parallel to each other, hence the two radicals interact on a triplet surface that forbids the formation of H2O2 and facilitates the production of oxygen in its ground state.

2018 - Spin-dependent electrochemistry: A novel paradigm [Articolo su rivista]
Fontanesi, Claudio
abstract

Here is reported a concise outline of a new paradigm we recently developed: spin-dependent electrochemistry (SDE). The main idea underlying the development of SDE relies on the implementation in an electrochemical system of the spin filtering effect of chiral systems (chiral induced spin selectivity, CISS effect). Results are illustrated in detail for two selected examples where spin polarized currents are observed and controlled in electrochemical-based experiments. All in all, the spin-dependent electrochemistry paradigm can be considered somehow equivalent to the spintronics concept, but transferred in the field of electrochemistry. Present perspectives and possible future developments relying on SDE potentiality are also addressed.

2018 - Spin-dependent electrochemistry: Enantio-selectivity driven by chiral-induced spin selectivity effect [Articolo su rivista]
Gazzotti, Mirko; Arnaboldi, Serena; Grecchi, Sara; Giovanardi, Roberto; Cannio, Maria; Pasquali, Luca; Giacomino, Agnese; Abollino, Ornella; Fontanesi, Claudio
abstract

Spin-Dependent Electrochemistry (SDE) is a new paradigm in electrochemistry where the electrochemical response of a chiral electrode|solution interface is studied as a function of spin-polarized current. In this work, the SDE concept is further developed exploring the use of the “chiral imprinting” concept, which is implemented in two different, complementary, ways i) a chiral compound in bulk solution to obtain chiral-induced spin selectivity effect at the ferromagnetic (FM) electrode surface ii) conversely, a chiral-ferromagnetic (CFM) hybrid working electrode is produced: nickel is electrochemically co-deposited with a chiral compound, L-ta or D-(−)-tartaric acid, which is added to the electrodeposition bath; this allows to obtain a chiral co-deposited nickel-tartaric acid (Ni-LTA or Ni-DTA) working electrode. As a further innovation, the ferromagnetic working electrode is prepared by direct Ni electrodeposition on the north, or south, pole of a permanent magnet. The electrochemical response of these two chiral imprinted systems is studied by comparing cyclic voltammetry (CV) curves. The latter are recorded in the potential range relevant to the Ni(III)/Ni(II) electrochemical equilibrium, and also in the presence of glucose in bulk solution. An impressive variation in peak potentials is found when comparing CVs recorded on the north, versus south, pole of the magnet (in particular, when the co-deposited CFM working electrode is used). These results are properly rationalized within the Chiral-Induced Spin Selectivity (CISS) effect.

2017 - An Integrated Theoretical/Experimental Study of Quinolinic-Isoquinolinic Derivatives Acting as Reversible Electrochromes [Articolo su rivista]
Sassi, Mauro; Salamone, Matteo M; Beverina, Luca; Longoni, Gianluca; Fontanesi, Claudio; Vanossi, Davide; Cigarini, Luigi; Ruffo, Riccardo
abstract

A series of compounds, featuring an ethenylic bridge and quinoline and isoquinoline end capping units possessing systematically varied substitution patterns, were prepared as molecular materials for electrochromic applications. The different structures were optimized in order to maximize the electrochromic contrast in the visible region, mostly by achieving a completely UV-absorbing oxidized state. Density functional theory (DFT) calculations are exploited in order to rationalize the correlation between the molecular structure, the functional groups' electronic properties, and the electrochemical behavior. It is shown that the molecular planarity (i.e. ring/ring pi conjugation) plays a major role in defining the mechanism of the electrochemical charge transfer reaction, while the substituent's nature has an influence on the LUMO energy. Among the compounds here studied, the (E)-10-methyl-9-(2-(2-methylisoquinolinium1- yl)-vinyl)-1,2,3,4-tetrahydroacri-dinium trifluoromethanesulfonate derivative shows the most interesting properties as an electrochromophore.

2017 - Control of Electrons' Spin Eliminates Hydrogen Peroxide Formation during Water Splitting [Articolo su rivista]
Mtangi, Wilbert; Tassinari, Francesco; Vankayala, Kiran; Vargas Jentzsch, Andreas; Adelizzi, Beatrice; Palmans, Anja R. A.; Fontanesi, Claudio; Meijer, E. W; Naaman, Ron
abstract

The production of hydrogen through water splitting in a photoelectrochemical cell suffers from an overpotential that limits the efficiencies. In addition, hydrogen-peroxide formation is identified as a competing process affecting the oxidative stability of photoelectrodes. We impose spin-selectivity by coating the anode with chiral organic semiconductors from helically aggregated dyes as sensitizers; Zn-porphyrins and triarylamines. Hydrogen peroxide formation is dramatically suppressed, while the overall current through the cell, correlating with the water splitting process, is enhanced. Evidence for a strong spin-selection in the chiral semiconductors is presented by magnetic conducting (mc-)AFM measurements, in which chiral and achiral Zn-porphyrins are compared. These findings contribute to our understanding of the underlying mechanism of spin selectivity in multiple electron-transfer reactions and pave the way toward better chiral dye-sensitized photoelectrochemical cells.

2017 - Displacement of polarons by vibrational modes in doped conjugated polymers [Articolo su rivista]
Anderson, M.; Ramanan, C.; Fontanesi, C.; Frick, A.; Surana, S.; Cheyns, D.; Furno, M.; Keller, T.; Allard, S.; Scherf, U.; Beljonne, D.; D’Avino, G.; von Hauff, E.; Da Como, E.
abstract

Organic pi-conjugated polymers are deemed to be soft materials with strong electron-phonon coupling, which results in the formation of polarons, i.e., charge carriers dressed by self-localized distortion of the nuclei. Universal signatures for polarons are optical resonances below the band gap and intense vibrational modes (IVMs), both found in the infrared (IR) spectral region. Here, we study p-doped conjugated homo-and copolymers by combining first-principles modelling and optical spectroscopy from the far-IR to the visible. Polaronic IVMs are found to feature absorption intensities comparable to purely electronic transitions and, most remarkably, show only loose resemblance to the Raman or IR-active modes of the neutral polymer. The IVM frequency is dramatically scaled down (up to 50%) compared to the backbone carbon-stretching modes in the pristine polymers. The very large intensity of IVMs is associated with displacement of the excess positive charge along the backbone driven by specific vibrational modes. We propose a quantitative picture for the identification of these polaron shifting modes that solely based on structural information, directly correlates with their IR intensity. This finding finally discloses the elusive microscopic mechanism behind the huge IR intensity of IVMs in doped polymeric semiconductors.

2017 - Ferrocene Molecular Architectures Grafted on Si(111): A Theoretical Calculation of the Standard Oxidation Potentials and Electron Transfer Rate Constant [Articolo su rivista]
Fontanesi, Claudio; Innocenti, Massimo; Vanossi, Davide; Da Como, Enrico
abstract

The standard oxidation potential and the electron transfer (ET) rate constants of two silicon-based hybrid interfaces, Si(111)/organic-spacer/Ferrocene, are theoretically calculated and assessed. The dynamics of the electrochemical driven ET process is modeled in terms of the classical donor/acceptor scheme within the framework of Marcus theory. The ET rate constants, k(ET), are determined following calculation of the electron transfer matrix element, V-RP, together with the knowledge of the energy of the neutral and charge separated systems. The recently introduced Constrained Density Functional Theory (CDFT) method is exploited to optimize the structure and determine the energy of the charge separated species. Calculated ET rate constants are k(ET) = 77.8s(-1) and k(ET) = 1.3 x 10(-9) s(-1), in the case of the short and long organic-spacer, respectively.

2017 - Magnetless Device for Conducting Three-Dimensional Spin-Specific Electrochemistry [Articolo su rivista]
Kumar, Anup; Capua, Eyal; Vankayala, Kiran; Fontanesi, Claudio; Naaman, Ron
abstract

Electron spin states play an important role in many chemical processes. Most spin-state studies require the application of a magnetic field. Recently it was found that the transport of electrons through chiral molecules also depends on their spin states and may also play a role in enantiorecognition. Electrochemistry is an important tool for studying spin-specific processes and enantioseparation of chiral molecules. A new device is presented, which serves as the working electrode in electrochemical cells and is capable of providing information on the correlation of spin selectivity and the electrochemical process. The device is based on the Hall effect and it eliminates the need to apply an external magnetic field. Spin-selective electron transfer through chiral molecules can be monitored and the relationship between the enantiorecognition process and the spin of electrons elucidated.

2016 - An Integrated Experimental/Theoretical Study of Structurally Related Poly-Thiophenes Used in Photovoltaic Systems [Articolo su rivista]
Vanossi, Davide; Cigarini, Luigi; Giaccherini, Andrea; da Como, Enrico; Fontanesi, Claudio
abstract

In this work, a series of eight thiophene-based polymers (exploited as “donors” in bulk heterojunction photovoltaics cells), whose structures were designed to be suitably tuned with the electronic characteristics of the [6,6]-Phenyl C61 butyric acid methyl ester (PCBM), is considered,. The electronic properties of the mono-, di-, trimeric oligomers are reckoned (at the Hartree-Fock and DFT level of the theory) and compared to experimental spectroscopic and electrochemical results. Indeed, electrochemical and spectroscopic results show a systematic difference whose physical nature is assessed and related to the exciton (electron-hole) binding energy (Je,h). The critical comparison of the experimental and theoretical band gaps, i.e., the HOMO-LUMO energy difference, suggests that electrochemical and DFT values are the most suited to being used in the design of a polythiophene-based p-n junction for photovoltaics.

2016 - An unforeseen polymorph of coronene by the application of magnetic fields during crystal growth [Articolo su rivista]
Potticary, Jason; Terry, Lui R.; Bell, Christopher; Papanikolopoulos, Alexandros N.; Christianen, Peter C. M.; Engelkamp, Hans; Collins, Andrew M.; Fontanesi, Claudio; Kociok Köhn, Gabriele; Crampin, Simon; Da Como, Enrico; Hall, Simon R.
abstract

The continued development of novel drugs, proteins, and advanced materials strongly rely on our ability to self-assemble molecules in solids with the most suitable structure (polymorph) in order to exhibit desired functionalities. The search for new polymorphs remains a scientific challenge, that is at the core of crystal engineering and there has been a lack of effective solutions to this problem. Here we show that by crystallizing the polyaromatic hydrocarbon coronene in the presence of a magnetic field, a polymorph is formed in a β-herringbone structure instead of the ubiquitous 3-herringbone structure, with a decrease of 35° in the herringbone nearest neighbour angle. The β-herringbone polymorph is stable, preserves its structure under ambient conditions and as a result of the altered molecular packing of the crystals, exhibits significant changes to the optical and mechanical properties of the crystal.

2016 - Dimensional changes in automotive Pouch Li-Ion Cells: A Combined Thermo-Mechanical/electrochemical study [Articolo su rivista]
Gibellini, Erica; Lanciotti, Claudio; Giovanardi, Roberto; Bononi, Massimiliano; Davolio, Giovanni; Marchetti, Andrea; Fontanesi, Claudio
abstract

In this work it is proposed an integrated measurement system able to measure simultaneously mechanical properties, dimensional variations and Young modulus, of a pouch lithium-ion battery under operative conditions. At the same time, the designed integrated system allows also the measurement of both electrochemical main quantities (current and potentials) and temperature distribution. The complex testing capabilities system was implemented in an owner-lab-made apparatus. Experimental data collected both under normal operational conditions, as well as on abused batteries, allow to establish safer operational limits and to determine proper operation conditions to prevent the battery malfunctioning.

2016 - Polymers for application in organic solar cells: Bithiophene can work better than thienothiophene when coupled to benzodithiophene [Articolo su rivista]
Parenti, Francesca; Ricciardi, Rosa; Diana, Rosita; Morvillo, Pasquale; Fontanesi, Claudio; Tassinari, Francesco; Schenetti, Luisa; Minarini, Carla; Mucci, Adele
abstract

The synthesis and characterization of two low band gap copolymers (P1 and P2) incorporating benzo[1,2-b:4,5- b’]dithiophene unit substituted with octylsulfanylthienyl groups (OSBT) are here reported. These materials, designed to be employed in polymer solar cells (PSCs), were obtained from alternating OSBT and bithiophene (P1) or thienothiophene (P2) units. Their structural electrochemical and photophysical properties were investigated. They are thermally stable and soluble in organic solvents from which they easily form films. They also form p-stacks in solution, in film and display a moderate solvatochromism. These polymers were tested with [70]PCBM in bulk-heterojunction (BHJ) PSCs where they act as donor materials and [70]PCBM is the electron acceptor. The best device, obtained using a 1:3 weight ratio for the P1:[70]PCBM blend, shows a PCE around 1.5%. A broad response from 350 to 700 nm is also observed in the external quantum efficiency (EQE) curves, wider for P1 with respect to P2.

2016 - Spin-Dependent Transport through Chiral Molecules Studied by Spin-Dependent Electrochemistry [Articolo su rivista]
Mondal, Prakash Chandra; Fontanesi, Claudio; Waldeck, David H.; Naaman, Ron
abstract

Molecular spintronics (spin + electronics), which aims to exploit both the spin degree of freedom and the electron charge in molecular devices, has recently received massive attention. Our recent experiments on molecular spintronics employ chiral molecules which have the unexpected property of acting as spin filters, by way of an effect we call "chiral-induced spin selectivity" (CISS). In this Account, we discuss new types of spin-dependent electrochemistry measurements and their use to probe the spin-dependent charge transport properties of nonmagnetic chiral conductive polymers and biomolecules, such as oligopeptides, L/D cysteine, cytochrome c, bacteriorhodopsin (bR), and oligopeptide-CdSe nanoparticles (NPs) hybrid structures. Spin-dependent electrochemical measurements were carried out by employing ferromagnetic electrodes modified with chiral molecules used as the working electrode. Redox probes were used either in solution or when directly attached to the ferromagnetic electrodes. During the electrochemical measurements, the ferromagnetic electrode was magnetized either with its magnetic moment pointing "UP" or "DOWN" using a permanent magnet (H = 0.5 T), placed underneath the chemically modified ferromagnetic electrodes. The spin polarization of the current was found to be in the range of 5-30%, even in the case of small chiral molecules. Chiral films of the l- and d-cysteine tethered with a redox-active dye, toludin blue O, show spin polarizarion that depends on the chirality. Because the nickel electrodes are susceptible to corrosion, we explored the effect of coating them with a thin gold overlayer. The effect of the gold layer on the spin polarization of the electrons ejected from the electrode was investigated. In addition, the role of the structure of the protein on the spin selective transport was also studied as a function of bias voltage and the effect of protein denaturation was revealed. In addition to "dark" measurements, we also describe photoelectrochemical measurements in which light is used to affect the spin selective electron transport through the chiral molecules. We describe how the excitation of a chromophore (such as CdSe nanoparticles), which is attached to a chiral working electrode, can flip the preferred spin orientation of the photocurrent, when measured under the identical conditions. Thus, chirality-induced spin polarization, when combined with light and magnetic field effects, opens new avenues for the study of the spin transport properties of chiral molecules and biomolecules and for creating new types of spintronic devices in which light and molecular chirality provide new functions and properties.

2016 - Structure, Stoichiometry, and Charge Transfer in Cocrystals of Perylene with TCNQ-Fx [Articolo su rivista]
Salzillo, Tommaso; Masino, Matteo; Kociok Köhn, Gabriele; Di Nuzzo, Daniele; Venuti, Elisabetta; Della Valle, Raffaele Guido; Vanossi, Davide; Fontanesi, Claudio; Girlando, Alberto; Brillante, Aldo; Da Como, Enrico
abstract

Semiconductor charge transfer (CT) cocrystals are an emerging class of molecular materials which combines the characteristics of the constituent molecules in order to tune physical properties. Cocrystals can exhibit polymorphism, but different stoichiometries of the donor-acceptor (DA) pair can also give different structures. In addition, the structures of the donor and acceptor as pristine compounds can influence the resulting cocrystal forms. We report a structural study on several CT cocrystals obtained by combining the polyaromatic hydrocarbon perylene with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and its fluorinated derivatives having increasing electronegativity. This is achieved by varying the amount of fluorine substitution on the aromatic ring, with TCNQ-F2 and TCNQ-F4. We find structures with different stoichiometries. Namely, the system perylene:TCNQ-F0 is found with ratios 1:1 and 3:1, while the systems perylene:TCNQ-Fx (x = 2, 4) are found with ratios 1:1 and 3:2. We discuss the structures on the basis of the polymorphism of perylene as pure compound, and show that by a judicious choice of growth temperature the crystal structure can be in principle designed a priori. We also analyze the structural motifs taking into account the degree of charge transfer between the perylene donor and the TCNQ-Fx acceptors and the optical gap determined from infrared (IR) spectroscopy. This family of materials exhibits tunable optical gaps in the near-IR (NIR), promising applications in organic optoelectronics.

2015 - A novel synthetic strategy for magnetite-type compounds. A combined experimental and DFT-computational study [Articolo su rivista]
Cigarini, Luigi; Vanossi, Davide; Bondioli, Federica; Fontanesi, Claudio
abstract

The dynamics of the early stage reaction between benzyl alcohol and Fe(acetylacetonate)3 is studied by exploiting the Dynamic Reaction Coordinate (DRC) approach, at the PBE0/6-31G* level of theory. Analysis of the DRC trajectory provides a detailed molecular insight into the catalytic effect observed in the acidic reaction environment, compared to the neutral one. The presence of an additional proton in the reaction system, meant to simulate an acidic reaction environment, dramatically affects the reaction path: both by decreasing the activation energy of the complex dissociation and leading to the formation of acetone.

2015 - Characterization of Conducting Polymers for Organic Solar Cells [Abstract in Atti di Convegno]
Parenti, Francesca; Tassinari, Francesco; Fontanesi, Claudio; Schenetti, Luisa; Morvillo, P.; Ricciardi, R.; Diana, R.; Minarini, C.; Lanzi, M.; Mucci, Adele
abstract

Thiophene based copolymers are widely studied as the donor active layer in bulk hetero junction polymer solar cells (PSCs). These copolymers, in some cases formed by an alternating structure of donor/acceptor units, can be fine tuned in their electronic energy levels in order to achieve better power conversion efficiencies values.1 The characterization of organic polymers for application in PSCs, or organic electronics in general, is multidisciplinary in nature, for it requires expertise within different branches of chemistry and at the border among chemistry, physics and engineering.2 As organic chemists, we have to check the structure and properties of these polymers and this is not always trivial. This contribution will be mainly focussed on the NMR characterization of polymers in solution and to the problems arising when aggregation occurs. This is particularly observed when benzodithiophene and thienothiophene (that are among the most popular units) are present in the backbone. NMR findings appear to be strongly correlated to solvatochromism or morphological properties

2015 - Chiral Conductive Polymers as Spin Filters [Articolo su rivista]
Mondal, Prakash Chandra; Kantor Uriel, Nirit; Mathew, Shinto P.; Tassinari, Francesco; Fontanesi, Claudio; Naaman, Ron
abstract

Conductive organic polymers are used in organic electronic devices and specifically in organic-based light-emitting diodes (OLEDs). It is expected that by controlling the spin of the electrons that are injected from and into these devices, their energy efficiency will increase significantly. However, it is commonly thought that this would require introducing ferromagnets into the device, which represents a technological challenge. We present data indicating that electron transport through a chiral conductive polymer is highly spin dependent; hence, the polymers themselves can serve as a spin filter and in principle, this may allow the operation of spin-OLED without any magnetic component.

2015 - Chiral conductive polymers as spin filters [Abstract in Atti di Convegno]
Tassinari, Francesco; Parenti, Francesca; Mondal, P. C.; Kantor ­‐Uriel, N.; Mathew, S. P.; Naaman, R.; Fontanesi, Claudio; Schenetti, Luisa; Mucci, Adele
abstract

We investigated spin-selective electron transport through poly{[methyl N -(tert-butoxycarbonyl)-S-3- thienyl- L -cysteinate]-cothiophene} (PCT-L)5. Measurements were performed in two configurations: in an electrochemical cell at room temperature or in a solid state device at various temperatures.

2015 - Field and chirality effects on electrochemical charge transfer rates: Spin dependent electrochemistry [Articolo su rivista]
Mondal, Prakash Chandra; Fontanesi, Claudio; Waldeck, David H.; Naaman, Ron
abstract

This work examines whether electrochemical redox reactions are sensitive to the electron spin orientation by examining the effects of magnetic field and molecular chirality on the charge transfer process. The working electrode is either a ferromagnetic nickel film or a nickel film that is coated with an ultrathin (5–30 nm) gold overlayer. The electrode is coated with a self-assembled monolayer that immobilizes a redox couple containing chiral molecular units, either the redox active dye toluidine blue O with a chiral cysteine linking unit or cytochrome c. By varying the direction of magnetization of the nickel, toward or away from the adsorbed layer, we demonstrate that the electrochemical current depends on the orientation of the electrons’ spin. In the case of cytochrome c, the spin selectivity of the reduction is extremely high, namely, the reduction occurs mainly with electrons having their spin-aligned antiparallel to their velocity.

2015 - How intermolecular geometrical disorder affects the molecular doping of donor-acceptor copolymers [Articolo su rivista]
Di Nuzzo, Daniele; Fontanesi, Claudio; Jones, Rebecca; Allard, Sybille; Dumsch, Ines; Scherf, Ullrich; Von Hauff, Elizabeth; Schumacher, Stefan; Da Como, Enrico
abstract

Molecular doping of conjugated polymers represents an important strategy for improving organic electronic devices. However, the widely reported low efficiency of doping remains a crucial limitation to obtain high performance. Here we investigate how charge transfer between dopant and donor–acceptor copolymers is affected by the spatial arrangement of the dopant molecule with respect to the copolymer repeat unit. We p-dope a donor–acceptor copolymer and probe its charge-sensitive molecular vibrations in films by infrared spectroscopy. We find that, compared with a related homopolymer, a four times higher dopant/polymer molar ratio is needed to observe signatures of charges. By DFT methods, we simulate the vibrational spectra, moving the dopant along the copolymer backbone and finding that efficient charge transfer occurs only when the dopant is close to the donor moiety. Our results show that the donor–acceptor structure poses an obstacle to efficient doping, with the acceptor moiety being inactive for p-type doping.

2015 - New one-step thiol functionalization procedure for Ni by self-assembled monolayers [Articolo su rivista]
Fontanesi, Claudio; Tassinari, Francesco; Parenti, Francesca; Cohen, Hagai; Mondal, Prakash Chandra; Kiran, Vankayala; Giglia, Angelo; Pasquali, Luca; Naaman, Ron
abstract

This article reports on a facile and fast strategy for the self-assembled monolayer (SAM) functionalization of nickel surfaces, employing cyclic voltammetry (CV) cycling of a suitable tailored solution containing the species to be adsorbed. Results are presented for ultrathin films formed on Ni by 1-hexadecanethiol (C16), L-cysteine (L-cys), and the polymethyl (2R)-3-(2,2'-bithiophen-4-ylsulfanyl)-2-[(tert-butoxycarbonyl)amino]propanoate (PCT-L) thiophene-based chiral polymer. The effective formation of high-quality ultrathin organic films on the nickel was verified both electrochemically and by exploiting typical surface characterization techniques such as contact angle, ellipsometry, atomic force microscopy (AFM), polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS).

2015 - Spin Filtering in Electron Transport Through Chiral Oligopeptides [Articolo su rivista]
Kettner, M.; Göhler, B.; Zacharias, H.; Mishra, D.; Kiran, V.; Naaman, R; Fontanesi, Claudio; Waldeck, David H.; Sek, Slawomir; Pawowski, Jan; Juhaniewicz, Joanna
abstract

We report on the observation of chirality induced spin selectivity for electrons transmitted through monolayers of oligopeptides, both for energies above the vacuum level as well as for bound electrons and for electrons conducted through a single molecule. The dependence of the spin selectivity on the molecular length is measured in an electrochemical cell for bound electrons and in a photoemission spectrometer for photoelectrons. The length dependence and the absolute spin polarization are similar for both energy regimes. Single molecule conductance studies provide an effective charge transport barrier between the two spin channels and it is found to be on the order of 0.5 eV.

2015 - The Role of the Electron Spin Polarization in Water Splitting [Articolo su rivista]
Mtangi, Wilbert; Kiran, Vankayala; Fontanesi, Claudio; Naaman, Ron
abstract

In this paper we show that in an electrochemical cell in which the photoanode is coated with chiral molecules, the over-potential required for hydrogen production drops remarkably, as compared with cells containing achiral molecules. The hydrogen evolution efficiency is studied comparing seven different organic molecules, three chiral and four achiral. We propose that the spin specificity of electrons transferred through chiral molecules is the origin of a more efficient oxidation process in which oxygen is formed in its triplet ground state. The new observations are consistent with recent theoretical works pointing to the importance of spin alignment in the water-splitting process.

2014 - A DFT COMPUTATIONAL STUDY OF STRUCTURALLY RELATED POLY-THIOPHENES USED IN PHOTOVOLTAIC SYSTEMS [Abstract in Atti di Convegno]
Fontanesi, Claudio; Vanossi, Davide; L., Cigarini; Mucci, Adele; E., Da Como
abstract

The electric properties of a large number of different complex composed systems (with particular focus on interfacial systems) are rationalized within a “Lego-like sum approach” of the electronic properties of the single components. Such a general modelistic approach span extremely different worlds: from Mott-Schottky barrier to Tafel plots in electrochemical systems [1,2]. In particular, in the field of organic semiconductors exploited to assemble photovoltaic devices, the open circuit potential is rationalized on the basis of the reciprocal HOMO LUMO energy differences between the donor and the acceptor partners [3]. Although such an approach seems by far too much crude in its strategy, the straight comparison of HOMO LUMO MOs energy levels, of the donor and acceptor building blocks, is yet the most widespread tools exploited in the modelization of photovoltaic organic based system [4]. In this work a series of seven thiophene based polymers (donors) are considered, whose structure was designed (both by introduction of ring structures of various chemical nature in the polymeric backbone structure – heteropolymers – and also by various lateral alkyl chains) so to suitably tune the electronic properties of the [6,6]-Phenyl C61 butyric acid methyl ester, often addressed as PCBM, (acceptor) and obtained a satisfactory solubility. Examples of the polymers structure are shown in Chart 1. The electronic properties of the mono-, di-, tri-meric oligomer species are reckoned and compared to experimental spectroscopic and electrochemical results.

2014 - Effect of the Electric Field on the Structure of a Chiral Conductive Polymer Thin Film [Abstract in Atti di Convegno]
Tassinari, Francesco; Mathew, S. P.; Fontanesi, Claudio; Schenetti, Luisa; Mucci, Adele; Naaman, R.
abstract

The chemical-physical properties of conductive polymer thin films are strictly related to the structure and conformations of the chains in the polymer lattice. Crystallinity, chain length, substituents, doping level are just some of the many variables that play a role in the final properties of the polymer films. Another key factor is the orientation of the chains inside the thin film. A polymer chain is anisotropic, and so are its properties. However, a lattice where the chains are randomly arranged will have the same properties no matter which direction we measure them, whereas an oriented lattice will show different properties related to the preferential order of the macromolecular structure. We used different electric fields to align the macromolecules of a chiral conductive polymer (CCP), capable of self-organizing in chiral helixes in the solid state, and we studied its effect on the anisotropy of the obtained thin films, on the structure of the aggregates and on the conductive properties of the polymer by means of different instrumental techniques. All the measurements showed a preferential alignment of the polymer chains after the process under applied electric field. Circular dichroism was used to probe the chirality of the polymer aggregates, and it was found that the field strongly influences the helical superstructures of the CCP. The use of the electric field to fine tune the helical structures of this chiral polymer stands out as an interesting possibility which we are currently investigating.

2014 - Electric Field-Driven Alignment of Chiral Conductive Polymer Thin Films [Articolo su rivista]
Tassinari, Francesco; Mathew, Shinto P.; Fontanesi, Claudio; Schenetti, Luisa; Naaman, Ron
abstract

We investigated the effect of an electric field on the alignment and structural properties of thin films of a chiral polybithiophene-based conductive polymer, functionalized with a protected l-cysteine amino acid. Thin films were obtained by exploiting both drop-casting and spin-coating procedures. The electric properties, the polarized Raman spectrum, the UV–vis spectrum, and the CD spectra were measured as a function of the electric field intensity applied during film formation. It was found that beyond the enhancement of the conductivity observed when the electric field aligns the polymer, the electric field significantly affects the chiral properties and the effect depends on the method of deposition.

2014 - Energy-Based Assessment of Optimal Operating Parameters for Coupled Biochar and Syngas Production in Stratified Downdraft Gasifiers [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; LA CAVA, Emma; Orlandi, Michele; Hanuskova, Miriam; Fontanesi, Claudio; Tartarini, Paolo
abstract

Biochar represents a valuable solution for carbon sequestration. Infact, it has aroused the interest of the scientific community due to its resistance to the degradation and its potential of soil improving. Stratified downdraft gasifier reactors are characterized by extreme design simplicity and it was proved that are able to operate with non-homogeneous feedstock. On the other hand, stratified reactors dispose a higher amount of char when compared to other downdraft gasifier. This work is aimed at characterizing the char produced through downdraft stratified reactors. Particular conditions which maximize both the quality and the amount of syngas and biochar was investigated. The whole system was evaluated through a composed coefficient Ip (performance index) which takes into account the energy content in the gas stream and the characteristics of the char produced. A lab-scale reactor, able to operate under different conditions, was designed considering the requirements of this work. It was implemented with a sophisticated heating system which allow us to control the reactor surface temperatures independently zone to zone. Results shown the capability of stratified gasifiers to be used for biochar disposal. Results outlined the Ip trend as function of the SV of the gasifier. and tar production was considered to find the more suitable condition.

2014 - Low band gap polymers for application in solar cells: synthesis and characterization of thienothiophene-thiophene copolymers [Articolo su rivista]
P., Morvillo; R., Diana; Fontanesi, Claudio; R., Ricciardi; M., Lanzi; Mucci, Adele; Tassinari, Francesco; Schenetti, Luisa; C., Minarini; Parenti, Francesca
abstract

In this paper we present the synthesis and characterization of two novel copolymers obtained from a bithiophene unit carrying octylsulfanyl side chains and thienothiophene units substituted with keto (PK) or ester (PE) groups. Their structural, electrochemical and photophysical properties were investigated by gel permeation chromatography (GPC), thermogravimetric analysis (TGA), NMR, UV-visible-NIR spectroscopy, cyclic voltammetry (CV) and atomic force microscopy (AFM). They possess good solubility in common organic solvents, filmability, proneness to form π-stacks, moderate solvatochromism, good thermal stability and low band gap energy. They were tested as donor materials in combination with [70]PCBM (electron acceptor) in bulk-heterojunction polymer solar cells. The geometry of the devices are: glass/ITO/PEDOT:PSS/ copolymer:[70]PCBM/Ca/Al. The external quantum efficiency curve of the best device, realized using a blend of PK:[70]PCBM, 1:2 weight ratio, shows a broad response from 350 to 1000 nm. The power conversion efficiency under 100 mW/cm2 AM 1.5G illumination is greater than 1%.

2014 - Polymer Solar Cells based on Benzodithiophene copolymers [Abstract in Atti di Convegno]
Parenti, Francesca; Diana, R.; Fontanesi, Claudio; Minarini, C.; Morvillo, P.; Ricciardi, R.; Schenetti, Luisa; Tassinari, Francesco; Mucci, Adele
abstract

Polymer solar cells are widely seen as the promise to a cheap alternative to the silicon-based ones. In addition to their low costs, they also have other advantages such as light weight, easy processability and compatibility with large scale flexible substrates, which make them suitable for a wide range of applications. However, the efficiency of photovoltaic energy conversion for these plastic devices is still low and this is limiting their commercial use. The efficiency of these polymeric photovoltaic cells got a significative increase when the bulk heterojunction (BHJ) configuration was introduced: it consists in an interpenetrating network of electron donor and acceptor materials that largely increases the active area and diminishes the distance that charge carriers have to travel. Recently, benzodithiophene (BDT) based polymers (Fig.1) have been used as electron donors in polymer solar cells showing very promising properties such as an increased charge transport and a red shift on the absorption spectra. In this work, the synthesis of different regioregular copolymers having substituted BDT as one of the monomers are described. The obtained polymers are characterized by spectroscopic and electrochemical techniques. Energy conversion measurements of BHJ solar cells produced with these polymers were conducted, and the electrical performances were compared in order to study the influence of the different comonomers on the overall efficiency of the devices.

2014 - Synthesis of low bandgap Thiophene-Based Copolymers: new donor material candidates in organic solar cells [Abstract in Atti di Convegno]
Parenti, Francesca; P., Morvillo; R., Diana; R., Ricciardi; C., Minarini; Fontanesi, Claudio; Mucci, Adele; A., Copelli; Schenetti, Luisa; Tassinari, Francesco
abstract

Polymer solar cells (PSCs) are emerging as promising alternatives to silicon-based solar cells [1] thanks to light weight, mechanical flexibility, processability and low costs. One of the common polymers used in PSCs are 3-alkyl substituted polythiophenes, but a low band gap alternative is needed in order to reach better cell performances [2]. Copolymers bearing thienothiophene (TT) and benzodithiophene (BDT) alternating units are widely studied as donor material in Bulk Heterojunction Cells [3]. In this poster communication we report on the synthesis and spectroscopic electrochemical, photovoltaic characterization of two thiophene based copolymers bearing thienyl substituted-BDT units alternating with bithiophene and TT-units respectively.

2013 - Editorial for the special issue on journal of electroanalytical chemistry [Articolo su rivista]
Marcaccio, M.; Fontanesi, C.; Paolucci, F.
abstract

2013 - Electrochemically assisted grafting of asymmetric alkynyl(aryl)iodonium salts on glassy carbon with focus on the alkynyl/aryl grafting ratio [Articolo su rivista]
Florini, Nicola; M., Michelazzi; Parenti, Francesca; Mucci, Adele; Sola, Marco; C., Baratti; De Renzi, Valentina; K., Daasbjerg; S. U., Pedersen; Fontanesi, Claudio
abstract

Glassy carbon (GC) surfaces are functionalized exploiting the electrochemical reduction of asymmetric iodonium salts of the general formula [4-Zsingle bondC6H4single bondI+single bondCtriple bond; length of mdashC(CH2)4Cl, Z = NO2, Br, F, H, or CH3]. The range of Z groups was selected aiming to examine the Carylsingle bondI bond energy as a function of the “electron withdrawing/electron donating” ability of the Z-group, with the ultimate purpose of controlling the alkynyl/aryl grafting ratio. The electroreduction mechanism and the characteristics of the grafted surface are studied by means of cyclic voltammetry and X-ray photoelectron spectroscopy. It is shown that the alkynyl/aryl grafting ratio decreases with the increasing electron withdrawing nature of Z, which induces a weakening of the Carylsingle bondI bond. Ab initio DFT vertical electron affinities (EAv) allowed to rationalize the electroreduction potentials of both the bulk and surface functionalised redox couples. Moreover, the alkynyl/aryl grafting ratio is assessed, at a molecular level, on the basis of ab initio DFT potential energy surfaces.

2013 - Electropolymerization of ortho-phenylenediamine. Structural characterisation of the resulting polymer film and its interfacial capacitive behaviour [Articolo su rivista]
Vanossi, Davide; Pigani, Laura; Seeber, Renato; Paolo, Ferrarini; Baraldi, Pietro; Fontanesi, Claudio
abstract

The physico-chemical characteristics of thin poly-(orth o-phenylenediamine) (PPD) films, obtained by electrochemical oxidation of the relevant monomer, are investigated using electrochemical, morpholog-ical and spectroscopic techniques. In particular, cyclic voltammetry and electroche mical impedance spec-troscopy (EIS) techniques are used to collect information concerning the redox, conductivity and double layer capacitance properties of the PPD film. AFM imaging and Raman spectroscopy results are exploited to characterize the film structure. In this respect, Raman spectra of two possible PPD oligomers are cal-culated at the B3LYP/6-311G level of the theory.

2013 - On the co-adsorption process of sodium dodecyl sulfate and sodium dodecylbenzenesulfonate on a 1-decanethiol-functionalized Au electrode, as a corrosion inhibiting mimic process [Articolo su rivista]
Fontanesi, Claudio; Camurri, Giulio; Tassinari, Francesco
abstract

The co-adsorption of sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS), on the 1-decanethiol self-assembled monolayer (SAM)-functionalized polycrystalline gold surface, is investigated by electrochemical techniques. The peak current (cyclic voltammetry) and charge transfer resistance (impedance spectra) variations are measured, concerning the [Fe(CN)6]3−/[Fe(CN)6]4− couple redox process. SDBS is found to yield a more efficient inhibiting barrier (towards the charge transfer process), when compared to the SDS one. Thus, it is suggesting that a higher tendency of SDBS to be co-adsorbed within the 1-decanethiol SAM with respect to SDS.

2013 - Regiochemistry in the electrochemical assisted grafting of glassy carbon. With focus on sterical hindrance of lateral chains in the electroreduction process of multi-functionalized bithiophene [Articolo su rivista]
Tassinari, Francesco; Vanossi, Davide; Mucci, Adele; Parenti, Francesca; Fontanesi, Claudio
abstract

The electrochemically assisted grafting process of glassy carbon (GC) surfaces is pursued by using the 7-[(5,50-diiodo-2,20-bithiophen-4-yl)sulfanyl]heptanenitrile (DIBHN). Which is an ad hoc synthesized bithiophene derivative: the DIBHN features two non-equivalent iodine substituents in the 5 (which is under the sterical hindrance of the sulfanylheptanenitrile group) and 50 positions. CV measurements show the occurrence of two reduction processes, the second, more cathodic one, induces the grafting. This result is in qualitative agreement with theoretical calculations (B3LYP/6-311G level of the theory) concerning the comparison of the optimized structures of the DIBHN neutral and radical anion species (first electroreduction process): the C–I bond length of the iodine in the 5 position varies from 2.098 (neutral) to 2.835 Å (radical anion), while the C–I bond length of the iodine in the 50 position remains virtually unchanged when comparing the geometries of the neutral and radical anion structures. Raman spectra are recorded for various polymer film thicknesses; the comparison with theoretical calculated Raman spectra further support the effective grafting of the glassy carbon surface.

2013 - Spin-dependent electron transmission through bacteriorhodopsin embedded in purple membrane [Articolo su rivista]
Mishra, Debabrata; Markus, Tal Z; Naaman, Ron; Kettner, Matthias; Göhler, Benjamin; Zacharias, Helmut; Friedman, Noga; Sheves, Mordechai; Fontanesi, Claudio
abstract

Spin-dependent photoelectron transmission and spin-dependent electrochemical studies were conducted on purple membrane containing bacteriorhodopsin (bR) deposited on gold, aluminum/aluminum-oxide, and nickel substrates. The result indicates spin selectivity in electron transmission through the membrane. Although the chiral bR occupies only about 10% of the volume of the membrane, the spin polarization found is on the order of 15%. The electrochemical studies indicate a strong dependence of the conduction on the protein's structure. Denaturation of the protein causes a sharp drop in the conduction through the membrane.

2013 - Synthesis and properties of new bio-functionalized polythiophenes [Altro]
Tassinari, Francesco; Fontanesi, Claudio; Mucci, Adele; Schenetti, Luisa
abstract

Polythiophenes are part of the family of conductive polymers. They are extremely popular nowadays for their promising applications in the organic solar cells. Their reactivity is very well established, and a large number of reaction for their modification is available in the literature. The possibility of tailoring these polythiophenes with a large library of different functional groups opens the door to a great number of possible applications. We synthesized two bio-functionalized polythiophenes, one bearing a cysteine aminoacid[1], the other an aniline ring acting as a linker for a laccase enzyme. The presence of the cysteine aminoacid in the side-chain of the polymer backbone gives to the polythiophene a very large circular dichroism activity, and the sign of the effect is related to the chirality of the attached aminoacid. The wavelenght of the CD effect is in the absorption zone of the thiophene rings, which is a strong proof to the presence of helicoidal arrangement of the polymer backbone in the polymer aggregates. The helicoidal structure is promoted by the side-chain aminoacid, and the chirality of the substituent influence the direction of the helix. This chiral conductive polymer and the helical structures that are present in its solid state are a perfect material to study the spin-conduction inside organic molecules (such as the Chiral Induced Spin Selectivity effect). The aniline substituted polymer has been designed to be used for bio-sensing applications. The thiophene substituted monomer is electropolymerized directly on the electrode surface, and the presence of the aniline allows the direct linking of the laccase enzyme to the electrode surface. The laccase enzyme catalyses the oxidation of phenols and polyphenols, and the product of the oxidation can be reduced at the electrode surface to give a signal proportional to the analyte concentration[2]. The same approach can be used for a large range of enzymes, giving this kind of polythiophene-based sensor engineering a wide applicability.

2012 - A novel copolymer from benzodithiophene and alkylsulfanyl-bithiophene: Synthesis, characterization and application in polymer solar cells [Articolo su rivista]
P., Morvillo; Parenti, Francesca; R., Diana; Fontanesi, Claudio; Mucci, Adele; Tassinari, Francesco; Schenetti, Luisa
abstract

In this paper we present the synthesis and characterization of a novel copolymer from thienothiophene and bithiophene units carrying nonanoyl and octylsulfanyl side chains, poly[1-(thieno[3,4-b]thien-2-yl)nonan-1-one-alt-4,4’-bis(octylsulfanyl)-2,2’-bithiophene] (PolyH). The structural, electrochemical and photophysical properties of PolyH were investigated by gel permeation chromatography (GPC), thermogravimetric analysis (TGA), NMR, UV-VIS-NIR spectroscopy and cyclic voltammetry (CV). PolyH possesses good solubility in common organic solvents, filmability, a proneness to form π-stacks and a moderate solvatochromism. PolyH was tested as donor material in combination with [70]PCBM (electron acceptor) in bulk-heterojunction polymer solar cells. The geometry of the device is: glass/ITO/PEDOT:PSS/ PolyH:[70]PCBM/Ca/Al. The external quantum efficiency curve of the best device (realized using a blend of PolyH:[70]PCBM, 1:2 weight ratio) shows a broad response from 350 to 1000 nm. The power conversion efficiency under 100 mW/cm2 AM 1.5G illumination is greater than 1%.

2012 - Functionalization of glassy carbon surface by means of aliphatic and aromatic amino acids. An experimental and theoretical integrated approach [Articolo su rivista]
Vanossi, Davide; Benassi, Rois; Parenti, Francesca; Tassinari, Francesco; Giovanardi, Roberto; Florini, Nicola; DE RENZI, Valentina; Arnaud, Gaelle Francoise; Fontanesi, Claudio
abstract

Glassy Carbon (GC) electrode surfaces are functionalized through electrochemical assisted grafting, in oxidation regime, of six amino acids (AA): -Alanine (-Ala), L-Aspartic acid (Asp), 11-aminoundecanoic acid (UA), 4-Aminobenzoic acid (PABA), 4-(4-Amino-phenyl)-butyric acid (PFB), 3-(4-Amino-phenyl)-propionic acid (PFP). Thus, a GC/AA interface is produced featuring carboxylic groups facing the solution. Electrochemical (cyclic voltammetry and electrochemical impedance spectroscopy) and XPS techniques are used to experimentally characterize the grafting process and the surface state. The theoretical results are compared with the experimental evidence to determine, at a molecular level, the overall grafting mechanism. Ionization Potentials, Standard Oxidation Potentials, HOMO and electron spin distributions are calculated at the CCD/6-31G* level of the theory. The comparison of experimental and theoretical data suggests that the main electroactive species is the “zwitterionic” form for the three aliphatic amino acids, while the amino acids featuring the amino group bound to the phenyl aromatic moiety show a different behaviour. The comparison between experimental and theoretical results suggests that both the neutral and zwitterionic forms are present in the acetonitrile solution in the case of 4-(4-Amino-phenyl)-butyric acid (PFB) and 3-(4-Amino-phenyl)-propionic acid.

2012 - Low band gap thienothiophene-thiophene copolymer: synthesis, characterization and application in polymer solar cells [Abstract in Atti di Convegno]
P., Morvillo; Parenti, Francesca; R., Diana; Fontanesi, Claudio; M., Lanzi; Mucci, Adele; Tassinari, Francesco; Schenetti, Luisa
abstract

Polymer solar cells (PSCs) have recently attracted considerable attention due to their advantages of low cost, light weight, processability and compatibility with large scale flexible substrates. The most efficient device architecture of polymer solar cells is based on the bulk heterojunction concept in which the active layer, sandwiched between two electrodes with different work functions, consists of a blend of electron donating material, e.g. a p-type conjugated polymer, and an electron accepting material (n-type), such as fullerene derivatives.Polythiophenes are quite interesting materials for this purpose, combining the above described advantages with an enhanced photochemical stability, compared with poly(p-phenylene vinylene) and poly p-phenylene. In this work the synthesis, the spectroscopic and photovoltaic characterization of a thienothiophene-thiophene copolymer are reported. Poly[2-nonanoylthieno[3,4-b]thiophene-4,6-diyl-alt-4,4’-bis(octylsulfanyl)-2,2’-bithiophene]) was obtained by Stille coupling between the dibromo derivative of 2-nonanoylthienothiophene and a distannyl derivative of bis(octylsulfanyl)bithiophene.Bulk heterojunction solar cells using these polymers as donor materials blended with PCBM as acceptor were prepared and investigated. The geometry of the device is: glass/ITO/PEDOT:PSS/Polymer:PCBM/Ca/Al. An efficient charge transfer between the donor and PCBM takes place and the best device obtained has and efficiency of 1% under simulated light (AM1.5G). Further improvement of the efficiency using different acceptors, optimizing layer thickness and lowering polymer impurities can be envisaged.

2012 - On the Hybrid Glassy Carbon Electrode/OligoThiophene/Ag(NP) Interface [Articolo su rivista]
Tassinari, Francesco; Tancini, Erik; Massimo, Innocenti; Schenetti, Luisa; Fontanesi, Claudio
abstract

GC/OligoThiophene/Ag(NP) hybrid interfaces are synthesized and characterized: GC is the glassy carbon surface; OligoThiophene stands for both an ultrathin bithiophene grafted film and a 4-Br-Bithiophene grafted polymer; Ag(NP) stands for silver nanoparticles. The hybrid interface preparation involves different steps: first, the electrode surface is functionalized through a combination of electrochemically assisted grafting (under reduction regime) and polymerization (under oxidation regime); then, silver nanoparticles are chemisorbed by dipping. In particular, an ultrathin film of grafted bithiophene can be obtained by applying one cyclic voltammetry reduction cycle (GC/BT surface), while subsequent cyclic voltammetry cycling under oxidation regime yields an immobilized 4Br-Bithiophene polymer (GC/4BrBT surface). AFM and TEM images were recorded to investigate the morphology and chemical composition of the Ag(NP). FeII/ FeIII cyclic voltammetry, Zn underpotential deposition (UPD), XPS, LA-ICP-MS, and Raman techniques were exploited to characterize both the GC/OligoThiophene and GC/OligoThiophene/Ag(NP) interfaces. Theoretical calculation, at the B3LYP/ 6-311G** level of the theory, enabled rationalization of the electroreduction mechanism and the Raman results.

2011 - (Alkylsulfanyl)bithiophene-alt-Fluorene: π-Conjugated Polymers for Organic Solar Cells [Articolo su rivista]
Parenti, Francesca; Pasquale, Morvillo; Eugenia, Bobeico; Rosita, Diana; Massimiliano, Lanzi; Fontanesi, Claudio; Tassinari, Francesco; Schenetti, Luisa; Mucci, Adele
abstract

We describe the synthesis of alternating bithiophene–fluorenecopolymers (P1–P3) with different regiochemistry of thebithienyl unit and different alkylsulfanyl chain lengths. Thestructural, electrochemical and photophysical properties ofthese polymers were investigated by gel permeationchromatography (GPC), differential scanning calorimetry(DSC), NMR, UV/Vis and photoluminescence (PL) spectroscopyand cyclic voltammetry (CV), and the polymerswere used to assemble organic solar cells (OSCs), in combi-IntroductionOrganic conjugated materials are attracting increased attentiondue to their potential in the fields of chemical sensors,[1] electroluminescent devices,[1c,2] field-effect transistors[3] and OSCs.[4] The last is one of the most appealingapplications of conjugated polymers because they have thepotential to be a low cost alternative to conventional inorganicsemiconductors.[5] The major desirable features ofOSCs are mechanical flexibility, very high speed of processingand low cost for large area fabrication.[6] The mostefficient device architecture of polymeric solar cells is basedon the bulk heterojunction concept (BHJ),[7] in which theactive layer, sandwiched between two electrodes with differentwork functions, consists of a blend of electron donatingmaterial, e.g. a p-type conjugated polymer, and an electronaccepting material (n-type), such as fullerene derivatives.For application in OSCs, conjugated polymers should[a] Dipartimento di Chimica, Università di Modena e ReggioEmilia,Via G. Campi 183, 41125 Modena, ItalyFax: +39-059373543E-mail: adele.mucci@unimore.it[b] ENEA, C.R. Portici,Piazzale E. Fermi 1, 80055 Portici (NA), ItalyE-mail: pasquale.morvillo@enea.it[c] Dipartimento di Chimica Industriale e dei Materiali, Universitàdi Bologna,V.le del Risorgimento 4, 40136 Bologna, ItalySupporting information for this article is available on theWWW under http://dx.doi.org/10.1002/ejoc.201100738.Eur. J. Org. Chem. 0000, 0–0 © 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1nation with the fullerene derivative methyl [6,6]-phenyl-C61-butyrate (PCBM). P3, with a head-to-head bithienyl unit,shows a broader absorption and a lower band gap with respectto P1 and P2, which have tail-to-tail bithienyl units.The PL intensity of P1–P3 is dramatically quenched in thepresence of PCBM, demonstrating that an efficient chargetransfer between donor and acceptor occurs. The best OSCdevice was obtained with P3.

2011 - Adsorption of organic compounds at the aluminium oxide/aqueous solution interface during the aluminium anodizing process [Articolo su rivista]
Giovanardi, Roberto; Fontanesi, Claudio; W., Dallabarba
abstract

The paper reports a systematic study concerning the role played by different organic compounds (glycolic acid, oxalic acid, glycerol) on the electrochemical oxidation process of aluminium in sulphuric acid solution. The result of the experiment as a whole provides a clear indication of the deep influence exerted by the three selected organic compounds on the aluminium oxide structure, leading to the formation of a more compact oxide layer. Electrochemical impedance spectroscopy results appear of particular interest; they are discussed in the light of a model proposed by Bojinov. The relevant parameters, half-jump distance a and cross-capture section S, are found consistently related to variations in the oxide structure (porosity). This gives a sounder basis to the physically correct nature of the assumptions underlying the Bojinov model, also suggesting that organic compounds are adsorbed at the aluminium oxide/aqueous solution interface.

2011 - Cobalt monolayer islands on Ag (111) for ORR catalysis [Articolo su rivista]
Loglio, Francesca; Lastraioli, Elisa; Bianchini, Claudio; Fontanesi, Claudio; Innocenti, Massimo; Lavacchi, Alessandro; Vizza, Francesco; Foresti, Maria Luisa
abstract

The design of a catalyst for one of the most important electrocatalytic reactions, the oxygen reduction reaction (ORR), was done following the most recent guidelines of theoretical studies on this topic. Aim of this work was to achieve a synergic effect of two different metals acting on different steps of the ORR. The catalytic activity of Ag, already known and characterized, was enhanced by the presence of a monolayer of cobalt subdivided into nanosized islands. To obtain such a controlled nanostructure, a novel method utilizing self-assembled monolayers (SAMs) as templates was employed. In a recent study, we were able to perform a confined electrodeposition of cobalt onto Ag(111) in a template formed by selectively desorbing a short-chain thiol (3-mercaptopropionic acid, MPA) from binary SAMs using 1-dodecanthiols (DDT). [32] This method allows for an excellent control of the morphology of the deposit by varying the molar ratio of the two thiols. Because cobalt does not deposit on silver at an underpotential, the alternative approach of surface limited redox replacement (SLRR) was used. This method, recently developed by Adžić et al.,13 consists of the use of a monolayer of a third metal, which can be deposited at an underpotential, as a template for the spontaneous deposition of a more noble metal. Herein, we choose zinc as template for the deposition of cobalt. Ag(111) crystals were covered by monolayer islands consisting of cobalt, with the surface atomic ratios ranging from 12 to 39 % for cobalt. The catalytic activity of such samples towards ORR was evaluated and the best improvement in activity was found to be that of the sample with a cobalt percentage of approximately 30 % with respect to the bare silver, which is in good agreement with theoretical hypotheses.

2011 - Dissociation Dynamics of Asymmetric Alkynyl(Aryl)Iodonium Radicals: An ab Initio DRC Approach to Predict the Surface Functionalization Selectivity [Articolo su rivista]
Fontanesi, Claudio; Bortolotti, Carlo Augusto; Vanossi, Davide; M., Marcaccio
abstract

The dissociation process of neutral open-shell [4-F—(C6H4)—I—CtC—(CH2)4—Cl] and [4-NO2—(C6H4)—I—CtC—(CH2)4—Cl] asymmetric iodonium radicals was studiedtheoretically. Vertical electron affinities and DRC (dynamic reactioncoordinate) results were obtained and compared with experimentalevidence. In particular, the fluorine and nitro substituent groups wereselected because of (i) their opposite electron-withdrawing/electrondonatingeffects and (ii) experimental evidence that the grafting ability,in terms of alkynyl/aryl grafting ratio, increases with decreasingelectron-withdrawing nature of the para-position substituent on the phenyl ring. DRC results show that the dissociation dynamicsof the iodinealkynyl carbon bond, for the nitro-substituted iodonium, occurs on a longer time scale than that of the fluorinesubstitutediodonium. This finding is in agreement with the overall experimental results.

2011 - Organic Materials for Phovoltaics: Synthesis and Electrochemical Behaviour of a Thiophene Based Copolymer [Abstract in Atti di Convegno]
Parenti, Francesca; R., Diana; Fontanesi, Claudio; P., Morvillo; Mucci, Adele; Schenetti, Luisa; Tassinari, Francesco
abstract

Polymer solar cells (PSCs) have recently attracted considerable attention due to their advantages of low cost, light weight, processability and compatibility with large scale flexible substrates [1]. Polythiophenes are quite interesting materials for this purpose, combining the above described advantages with an enhanced photochemical stability, compared with poly(p-phenylene vinylene) and poly p-phenylene.In this communication the synthesis, the spectroscopic, the electrochemical and photovoltaic characterization of a thiophene based copolymerare reported. The synthesis was performed in analogy to ref. [2] via Stille coupling of a brominated and a stannilated comonomer as illustrated in Fig.1. The copolymer was characterised through 1H and 13C NMR, Uv-Vis spectroscopy, Cyclic Voltammetry.References[1] S. Gunes, H. Neugebauer, N. S. Sariciftci, “Conjugated Polymer-Based Organic Solar Cells” Chem. Rev. 107, 1324 (2007) ; M. Helgesen, R. Søndergaard, F. C. Krebs, “Advanced materials and processes for polymer solar cell devices”, J. Mater. Chem. 20, 36 (2010) ; J. Peet, J. Y. Kim, N. E. Coates, W. L. Ma, D. Moses, A. J. Heeger, G. C. Bazan, “Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols”, Nat. Mater. 6, 497 (2007) ; S. A. Gevorgyan and F. C. Krebs in Handbook of thiophene-Based materials, I. F. Perepichka and D. F. Perepichka ed. (John Wiley and Sons Ltd., 2009). [2]Yongye Liang, Danqin Feng, Yue Wu, Szu-Ting Tsai, Gang Li, Claire Ray and Luping Yu, “Highly Efficient Solar Cell Polymers Developed via Fine-Tuning of Structural and Electronic Properties”, JACS 131, 7792-7799 (2009)

2011 - Preparation and characterization of bithiophene modified Si(1,1,1) electrodes [Abstract in Atti di Convegno]
Tassinari, Francesco; Fontanesi, Claudio; Mucci, Adele; Parenti, Francesca; Schenetti, Luisa
abstract

The purpose of this work is to prepare a substituted oligothiophene (OT) modified electrode, in which the oligomer is capable of acting as a conductive wire between the electrode surface and the solution bulk.A simple model system is represented by a bithiophene chemically grafted to the surface of a hydrogen terminated n-doped Si(111) electrode. The possibility to functionalize with different moieties the lateral chain and the thiophene rings makes these systems very versatile and easily customizable.

2010 - Entropy Variation in the Two-dimensional Phase Transition of Anthracene Adsorbed at the Hg Electrode/Ethylene Glycol Solution Interface [Articolo su rivista]
Fontanesi, Claudio
abstract

The adsorption of anthracene (C14H10), at the mercury electrode/ethylene glycol(EG) solution interface, is characterized by a low and almost constant capacity (about8 μF cm−2) region (capacitive “pit” or “plateau”) in capacity vs. potential curves, uponselection of suitable values of temperature, bulk concentration and applied potential values.This result is rationalized assuming the occurrence of a 2D phase transition betweentwo distinct adsorbed phases: (i) a “disordered” phase, characterized by a flat “parallel”disposition of the aromatic moiety on the electrode surface (ii) an “ordered” phase,characterized by a “perpendicular” disposition of the aromatic moiety on the electrodesurface. The experimental evidence is rationalized by considering the chemical potential asan explicit function of the “electric field/adsorbed molecule” interaction. Such a modelisticapproach enables the determination of the relevant standard entropy variation.

2010 - Experimental and Theoretical Study of the p- and n-Doped States of Alkylsulfanyl Octithiophenes [Articolo su rivista]
C., Bruno; F., Paolucci; M., Marcaccio; Benassi, Rois; Fontanesi, Claudio; Mucci, Adele; Parenti, Francesca; L., Preti; Schenetti, Luisa; Vanossi, Davide
abstract

The charge-transfer and spectral properties of two octithiophenes, namely 4′,4′′′,3′v,3v′-tetra(octylsulfanyl)-2,2′:5′,2′′:5′′,2′′′:5′′′,2′v:5′v,2v:5v,2v′:5v′,2v′′-octithiophene and 4,3′′,4v,4v′′-tetrabromo-4′,4′′′,3′v,3v′-tetra[(R)-2-methylbutylsulfanyl]-2,2′:5′,2′′:5′′,2′′′:5′′′,2′v:5′v,2v:5v,2v′:5v′,2v′′-octithiophene, OT1 and OT2, respectively,are characterized by cyclic voltammetry and spectroelectrochemistry under ultradry conditions. The analysisof the voltammetric results shows the formation of up to the dication for both OT1 and OT2 and up to thetetraanion (OT1) and trianion (OT2) anions. The optical properties of the OT1 (2+, 1+, neutral, 1-, 2-)species were probed by in situ UV-vis-NIR spectroelectrochemistry. The calculated standard potentials atthe B3LYP/cc-pVTZ level of the theory allowed the rationalization of the experimental electrochemical results.The UV-vis-NIR spectra were successfully compared with the theoretical electronic transitions and oscillatorstrength data obtained by time-dependent B3LYP/6-31G* calculations. Theoretical redox potentials and opticaltransitions properties are calculated including “the solvent effect” within the CPCM model. The consistencyobtained between experimental and theoretical results indicates the existence of the hypothesized high-spin/high-charge p- and n-doped electronic states for the OT1 and OT2 octithiophenes here studied.

2010 - On the Electroreduction Mechanism of Iodonium Salts on Glassy Carbon Electrodes" [Abstract in Atti di Convegno]
K., Daasbjerg; S. U., Pedersen; Florini, Nicola; Parenti, Francesca; Bortolotti, Carlo Augusto; Vanossi, Davide; Fontanesi, Claudio
abstract

Glassy carbon (GC) surfaces can be functionalized exploiting the electrochemical reduction of iodonium salts of general formula [RIR’]+ [1]. The overall mechanism could be roughly sketched as: IR’ bond cleavage:[RIR’]+ + e + GC  R’GC + IR Route (1) IR bond cleavage:[RIR’]+ + e + GC  RGC + IR’ Route (2) Upon electroreduction the I-R or the I-R’ bond dissociate, leading to a neutral closed shell organic iodide and an open shell radical, the latter reacts with the GC electrode (grafting). Several factors can influence the R/R’ ratio grafted on the GC surface. In fact, different amounts of the R and R’ radicals can be formed depending on the electronic structure of the neutral open shell [R-I-R’] • radical. Moreover, the different radicals can exhibit different reactivity toward the carbon surface, as well as different electrochemical stabilities (the radical itself could be reduced to a negative closed shell form). To clarify the interplay of the various factors affecting the final surface functionalization, a number of iodoniums has been considered and experimental evidences (electrochemical and XPS) are compared with theoretical results calculated at the DFT level of the theory (electron affinities, potential energy surfaces of competitive reaction pathways).

2010 - On the electroreduction mechanism of iodonium salts on glassy carbon electrodes [Abstract in Atti di Convegno]
K., Daasbjerg; S. U., Pedersen; DE RENZI, Valentina; Florini, Nicola; Parenti, Francesca; Bortolotti, Carlo Augusto; Vanossi, Davide; Fontanesi, Claudio
abstract

Glassy carbon (GC) surfaces can be functionalized exploiting the electrochemical reduction of iodonium salts of general formula [RIR’]+ [1]. The overall mechanism could be roughly sketched as: IR’ bond cleavage: [RIR’]+ + e + GC  R’GC + IR Route (1) IR bond cleavage: [RIR’]+ + e + GC  RGC + IR’ Route (2) Upon electroreduction the I-R or the I-R’ bond dissociate, leading to a neutral closed shell organic iodide and an open shell radical, the latter reacts with the GC electrode (grafting). Several factors can influence the R/R’ ratio grafted on the GC surface. In fact, different amounts of the R and R’ radicals can be formed depending on the electronic structure of the neutral open shell [R-I-R’] • radical. Moreover, the different radicals can exhibit different reactivity toward the carbon surface, as well as different electrochemical stabilities (the radical itself could be reduced to a negative closed shell form). To clarify the interplay of the various factors affecting the final surface functionalization, a number of iodoniums has been considered and experimental evidences (electrochemical and XPS) are compared with theoretical results calculated at the DFT level of the theory (electron affinities, potential energy surfaces of competitive reaction pathways).

2010 - Study of the metal complexation-ability of Nitrile functionalised oligo and polythiophenes: synthesis and study of the metal complexation-ability [Abstract in Atti di Convegno]
Parenti, Francesca; Fontanesi, Claudio; Schenetti, Luisa; Mucci, Adele
abstract

The synthesis and the complexation properties of some β-sulfanylheptanenitrile functionalised oligo- and polythiophenes reported are studied. The ability of these polymers towards the complexation of different transition metals is compared, in order to get insight into the influence of the substitution density and of the conjugation length on the chelating skills. The complexation-ability is a crucial property in view of possible applications of these materials as chemical sensors for metal ions detection1 or as carbon substitute materials for catalyst support for oxygen reduction or methanol oxidation in direct methanol fuel cells2 (DMFC).References:1) J. Maiti, B. Pokhrel, R. Boruah, S.K.Dolui, Sensors and Actuators B: Chemical 2009, 141,447-451; A.Pietrangelo, M. N. Roberts, M. J. MacLachlan, M.O.Wolf, Polymer Preprints 2009, 50, 280.2) M. Saito, H. Shiroishi, C.to Onoa, S. Tsuzuki, T. Okadaa, Y. Uchimoto, Journal of Molecular Catalysis A: Chemical 2006, 248, 99–108; R. P. Kingsborough, T. M. Swager, Chemistry of Materials 2000, 12, 872-874.

2009 - Electrochemical and Theoretical Investigation of Corannulene Reduction Processes [Articolo su rivista]
C., Bruno; BENASSI, Rois; PASSALACQUA, Alessio; F., Paolucci; FONTANESI, Claudio; M., Marcaccio; E. A., Jackson; L. . T., Scott
abstract

The voltammetric generation of corannulene anions was investigated over a large range of experimentalconditions comprising either “traditional” electrochemical solvents, such as dimethylformamide, acetonitrile,and tetrahydrofuran, or “unconventional” solvents, such as liquid ammonia, liquid methylamine, or liquiddimethylamine, and several different supporting electrolytes. Strong ion pairing effects were found to dominatethe electrochemical generation of corannulene higher anions, and through the suitable choice of the solvent/electrolyte system, we observed, for the first time, the reversible electrochemical generation of up to thetriply reduced corannulene. The standard potentials obtained experimentally compared rather well with thetheoretical values calculated by ab initio and density functional methods, in which solvation and ion pairingeffect were explicitly taken into account. In particular, the calculations considered the effect of the electrolytecation size on ion pairing in order to rationalize the occurrence of the third reduction within the experimentalpotential window.

2009 - Experimental and theoretical investigation of the p- and n-doped states of alkylsulfanyl octithiophenes [Abstract in Atti di Convegno]
Fontanesi, Claudio; C., Bruno; M., Marcaccio; F., Paolucci; Benassi, Rois; Bortolotti, Carlo Augusto; Mucci, Adele; Parenti, Francesca; Preti, Lisa; Schenetti, Luisa
abstract

Thiophene based materials, oligothiophenes as well, are promising candidates for technological applications, being a possible alternative to high-cost traditional materials for electronics such as silicon. Thus, in this work the charge-transfer properties oftwo structurally related (Si and S2 as sketched on the left) octithiophenes are studied by means of cyclic voltammetryr”(CV). Digital simulations of CV data ,I— , suggest the reversible formation of up to the dication, for both Si and S2, andup to the 4- (Si) and 3- (S2) anions. The ‘ ‘electronic structure of the Si species (2+, i+, neutral, 1-, 2-) is probed by UV/Vis-NIR “in-situ” spectroelectrochemistry. Experimental results are compared to standard potentials calculated at the B3LYP/cc-pVTZ level of the theory and to electronic transition energy and oscillator strength data reckoned by time dependent B3LYP/6 calculations. The consistency observed between experimental and theoretical results indicates the existence, as stable species, of the hypothesized high-spin/high-charge p- and n-doped electronic states.

2009 - Experimental and theoretical investigation of the p- and n-doped states of alkylsulfanyl octithiophenes [Abstract in Atti di Convegno]
Fontanesi, Claudio; C., Bruno; M., Marcaccio; F., Paolucci; Benassi, Rois; Bortolotti, Carlo Augusto; Mucci, Adele; Parenti, Francesca; Preti, Lisa; Schenetti, Luisa
abstract

We characterizad the charge-transfer properties of two octithiophenes by means of cylcic voltammetry, UV-Vis-NIR spectroelectrochemistry and DFT calculations.

2009 - Thermodynamics and kinetics of the electron transfer process of spinach plastocyanin adsorbed on a modified gold electrode [Articolo su rivista]
Ranieri, Antonio; Battistuzzi, Gianantonio; Borsari, Marco; Casalini, Stefano; Fontanesi, Claudio; Monari, Stefano; Siwek, MICHAL JAN; Sola, Marco
abstract

The reduction thermodynamics (DH0 rc and DS0 rc) and the kinetics of electron transfer for spinach plastocyaninadsorbed on a polycrystalline gold electrode coated with a mixed SAM made of 11-mercapto-1-undecanol and 11-mercapto-1-undecanoic acid were determined through cyclic voltammetry. Theadsorbed protein experiences a marked enthalpic stabilization of the oxidized state, likely due to the electrostaticinteraction of surface lysine(s) with the negatively charged SAM. The kinetic data indicate thatthe electron transfer process occurs through a tunnelling mechanism and that the distance between theprotein and the electrode surface can be calculated by the Marcus equation. The ionic strength of thesolution remarkably affects both the thermodynamics and the kinetics of the electron transfer processin a fashion which, for the former parameters, adheres to the Debye–Hückel model.

2008 - CHROMIUM ELECTRODEPOSITION FROM Cr(VI) LOW CONCENTRATION SOLUTIONS. [Articolo su rivista]
Fontanesi, Claudio; Giovanardi, Roberto; Cannio, Maria; E., Soragni
abstract

This work presents a study of a hard chromiumplating process using low concentration H2CrO4 baths. Inparticular, the effect of different values of CrO3/H2SO4 ratioon coating properties such as adhesion, hardness, surfaceroughness, apparent density and microstructure were considered.To increase the solution conductivity, avoiding longdeposition times and low throwing power typical of dilutesolutions, the behaviour of various inorganic compoundswas investigated. Specifically, the compounds suitable forobtaining brighter coatings with lower surface roughnessvalues than those obtained using Fink’s solutions wereNa2SO4 and Al2(SO4)3 9 18H2O. A bath composition wasidentified, with a limited use of Cr(VI) in a solution able toproduce coatings with a better surface roughness than thoseof conventional industrial baths.

2007 - An Ab-initio theoretical study of the electrochemical grafting process of alkynil(aryl)iodonium salts on glassy carbon surfaces [Relazione in Atti di Convegno]
K., Daasbjerg; DEL PENNINO, Umberto; DE RENZI, Valentina; Fontanesi, Claudio; Parenti, Francesca; Rastelli, Augusto
abstract

The behaviour of alkynil(aryl)iodonium salts upon electrochemical reduction, on glassy carbon electrodes, is here studied by comparing both theoretical and experimental results. In particular, experimental results are obtained by means of cyclic voltammetry and chronocoulometric measurements as well as by collecting XPS spectra, while the standard electrode potential and different dissociation paths (I-C, arylic, compared to the I-C, alkynil, bond cleavage) have been characterized theoretically at the B3LYP/3-21g** level of the theory (the solvation free Gibbs energy of the cation and of the neutral radical species have been calculated by using the CPCM method).

2007 - Electrochemistry and spectroelectrochemistry of polypyridine ligands: A theoretical approach [Articolo su rivista]
Marcaccio, M; Paolucci, F; Fontanesi, Claudio; Fioravanti, G; Zanarini, S.
abstract

The 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) and 2,5-bis(2'-pyridyl)pyrazine (2,5-dpp) have been successfully used as bridging ligands for building up ruthenium (II) and osmium (II) polypyridyl redox and luminescent active dendrimers. Such ligands have been herein investigated by ab initio and DFT theoretical calculations both in gas phase and with the solvent effect. The different molecular conformations exhibited by 2,3-dpp, which depend on whether it is free or coordinated to one or two metal centres, have been explored by performing the scan of the potential energy surface. The spectra of the neutral and the radical anion species of the relevant conformers have been calculated at DFT and semiempirical level of the theory. The results have been assessed by correlating them with electrochemical and UV-Vis-NIR spectroelectrochemical experimental ones, obtained in highly aprotic and dry conditions. (c) 2006 Elsevier B.V. All rights reserved.

2006 - Symmetric Octithiophenes: One-Pot Synthesis and ElectrochemicalProperties [Abstract in Atti di Convegno]
Preti, Lisa; Mucci, Adele; Schenetti, Luisa; Parenti, Francesca; Cagnoli, Rita; Passalacqua, Alessio; Benassi, Rois; Fontanesi, Claudio; Ferrarini, Paolo; F., Paolucci; M., Marcaccio; C., Bruno
abstract

sono stati riportati le sintesi di octatiofeni simmentrici ottenuti per accoppiamento ossidativo con FeCl3 e la loro caratterizzazione spettroscopica ed elettrochimica

2005 - Modelling of the initial stages of the electropolymerization mechanism of o-phenylenediamine [Articolo su rivista]
G., Camurri G; P., Ferrarini; Giovanardi, Roberto; Benassi, Rois; Fontanesi, Claudio
abstract

A detailed mechanism is proposed concerning the initial stages (up to the formation of the dimer) of the electropolymerization of ortho-phenylenediamine (oPD) to yield the polymer (PPD). Cyclic voltammetry measurements have been performed aiming to single out the effect of pH and to determine the number of exchanged electrons. The experimental evidence has been modelled considering 10 possible monomers (as obtained from the combination of oxidation and protonation/deprotonation reactions) involved in nine reactions to produce five different dimer species. Such a modelistic picture developed starting from the experimental findings, collected both in this paper and as found in the literature, is tightly compared with theoretical calculations. In particular, both E-0 values and thermodynamic quantities (Delta U, Delta H and Delta G variations), relating to the reaction path leading to the formation of the dimer, have been determined at the ab initio level of the theory (molecular structures relevant to transient complex species and transition states, as well as reaction free energy variations and activation energies were calculated too).

2005 - On the electroreduction of Cr(VI) aqueous solutions on iron and copper cathodes [Articolo su rivista]
Giovanardi, Roberto; E., Soragni; Fontanesi, Claudio; DE RENZI, Valentina; DEL PENNINO, Umberto; M. L., Foresti
abstract

The electroreductive behaviour of CrO3 +H2SO4 aqueous solution is studied on poly-crystalline iron and copper cathodes. Theelectrochemical results have been also compared with XPS, AFM and SEM findings collected ‘‘ex situ’’ on emersed electrodes andan electrochemical mechanism featuring adsorbed Cr(IV) and Cr(III) species is proposed. In the case of iron a main role is played bythe passive state of the electrodic surface caused by the presence of a protective mixed iron/chromium oxide layer and by its electrochemicaldissolution. This passive to active transition of the electrodic surface and the occurrence of an irreversible reductivecurrent peak, in a potential range where the deposition of metallic chromium does not yet occur, suggests that the electrodic surfaceplays an active role in the electrochemical process. A major difference is found between Fe and Cu cathodes, concerning the kineticmechanism of formation of adsorbed species.

2004 - Calculated electron affinities and redox E° values of polypyridinic derivatives [Articolo su rivista]
Benassi, Rois; Ferrarini, P.; Fontanesi, Claudio; Benedetti, Luca; Paolucci, F.
abstract

Quantum mechanical based ab-initio calculations are used to compute one-electron electrochemical standard reduction potentials, E-0, for a set of 12 polypyridinic derivatives (plus nitrobenzene and benzophenone as reference compounds) in dimethylformamide solution. Linear relationships between theoretical predictions and experimental data are constructed and provide a mean unsigned error of about 0.19 V. It is shown that the theoretical approach allows us also to discuss structural features related to the electron transfer process, like conformational changes found between the neutral and radical anion species (for instance, in the case of 4-4´dipyridyl a variation is found from 36degrees to almost zero of the ring-ring dihedral angle and a shortening of the single C-C bond when passing from the neutral to the radical anion). Also the weight of different terms (mainly: electron affinity, solvation Gibbs energies, DeltaG(0) of the 1/2 H-2(g), H-aq(+) + e(-) half-cell reaction) leading to the determination of E-0 is assessed on a quantitative basis.

2004 - On the 2D phase transition of adenine adsorbed at the Mercury/ethylene glycol solution interface [Articolo su rivista]
Fontanesi, Claudio; L., Benedetti; Giovanardi, Roberto; G., Camurri; P., Ferrarini
abstract

The liquid like → solid like 2D phase transition of adenine adsorbed at the Hg/ethylene glycol solution interface is here studied. Equilibrium aspects are effectively rationalized by using a model which was originally developed in the case of the 2D phase transition of adenine adsorbed at the Hg/aqueous solution interface [1,2]. In this work, the attention is mainly focused on the validation of the model itself in the case of a solvent different from water. The results obtained in the two different solvents are then compared in terms of structural (orientation of the adsorbate at the interface) and related thermodynamic (liquid like → solid like 2D standard entropy variation) properties. It is also found thatthe kinetics of formation of the 2D solid like phase follows a nucleation and growth mechanism, again in close similarity with the results obtained in water.

2003 - Decrease in toxic potential of mixed tensides maintained below the critical micelle concentration: An in vitro study [Articolo su rivista]
Benassi, Luisa; Bertazzoni, Giorgia; Magnoni, Cristina; Rinaldi, M; Fontanesi, Claudio; Seidenari, Stefania
abstract

Sodium lauryl sulphate (SLS) is an anionic tenside widely utilized in commercial topical preparations that may cause skin irritation. It has been shown that the barrier damage caused by SLS in vivo is lower when SLS is used in combination with other tensides which are able to reduce the critical micelle concentration (CIVIC). The aim of our study was to evaluate if the cytotoxic effect of SLS is reduced by the association with different tensides also at concentrations well below the CIVIC. Normal human keratinocytes from plastic surgery were grown in serum-free medium. At subconfluency, the cells were treated with SLS at a dose of 0.0025% in combination with cocamidopropyl betaine, Tween 20 and Tween 80 at the minimum toxic dose. Following tenside treatment, the culture medium was changed, and after 24 h the cells were collected for H-3-thymidine incorporation, the MTT (3-[4,5-dimethylthiazol2-yl]-2,5-diphenyl tetrazolium bromide) assay and neutral red (NR) uptake. The cytotoxic effect on normal human keratinocytes, as evaluated by 3H-thymidine incorporation, MTT assay and NR uptake, was significantly decreased by the combination with all the tested tensides. The correlation between cytotoxicity and physical properties was also studied by a conductimetric assay to investigate the mechanism involved in this toxicity reduction. Copyright

2003 - HREELS study of the adsorption mechanism and orientational order of 2-mercaptobenzoxazole on Cu(100) [Articolo su rivista]
F., Allegretti; DE RENZI, Valentina; Biagi, Roberto; DEL PENNINO, Umberto; G., Contini; V., DI CASTRO; C., Mariani; M. G., Betti; Fontanesi, Claudio
abstract

Organic molecules with sulfur-containing headgroups interacting with noble metal surfaces represent a fruitful class of systems with potential relevance in new device technology. Within this context, the room temperature adsorption of 2-mercaptobenzoxazole (MBO) on the Cu(1 0 0) surface has been studied by high-resolution electron energy-loss spectroscopy (HREELS) as a function of molecular exposure. At low coverage, the HREEL spectra present only one mode at 93 meV (750 cm(-1)), which is attributed to the out-of-plane C-H bending gamma(CH). Its off-specular angular dependence indicates that the molecules lie almost flat on the surface. At higher coverage, the MBO layer orders in a p(2 x 2) superstructure, and energy loss peaks at higher energies appear. These features can be assigned to in-plane vibrations indicating that the molecular axis tilts toward a more vertical position, thus allowing a closer molecular packing. Assignment of the HREELS peaks is confirmed by estimation of the gas phase normal modes of the free molecule, evaluated by ab initio methods. The absence of the N-H stretching mode in the HREEL spectra indicates that the H atom bonded to nitrogen in the gas-phase molecule is lost upon adsorption, suggesting that MBO molecule adsorbs on the Cu surface as a thiolate.

2003 - Substituent effects in the reduction behaviour of thio- and oxopyrimidines in non-aqueous solvents [Articolo su rivista]
Borsari, Marco; Cannio, Maria; Dallari, D; Fontanesi, Claudio; Gavioli, Giovanna; Peressini, S; Tavagnacco, C.
abstract

The electrochemical reduction of a series of thio- and oxopyrimidine derivatives has been investigated in organic solvents on mercury electrodes. In all cases the electrochemical process gave a dimeric species as the major product. The overall reduction mechanism is the same for oxo and thio derivatives, and is found to be dependent only on the nature of the ring nitrogen substituent. A 'father-son reaction' is observed when hydrogen is bound to the ring nitrogen atom: the radical anion obtained from the first electron transfer draws out the nitrogen proton of a nonreduced molecule and this then dimerizes. In the presence of a protonating agent as well as for the N-substituted derivatives, the 'father-son reaction' is not observed. Theoretical calculations have been performed to gain insight into the proposed mechanisms: the LUMO energy and the vertical electron affinity show a linear correlation with the reduction potentials. Analysis of the theoretical parameters has allowed step-by-step determination of the electrochemical reduction process. The manner in which solvent properties influence electrochemical behaviour has been examined, and the role of the acceptor number (AN) has been discussed.

2003 - Temperature Effect on the 2D phase transition kinetics of adenine adsorbed at the Hg electrode/aqueous solution interface [Articolo su rivista]
Fontanesi, Claudio; R., Andreoli; L., Benedetti; Giovanardi, Roberto
abstract

The kinetics of the liquid-like → solid-like 2D phase transition of adenine adsorbed at the Hg/aqueous solution interface is studied. Attention is focused on the effect of temperature on the rate of phase change; an increase in temperature is found to cause a decrease of transition rate.

2002 - Computational electrochemistry. Ab-initio calculation of solvent effect in the multiple electroreduction of polypyridinic compounds [Articolo su rivista]
Fontanesi, Claudio; Benassi, Rois; Giovanardi, Roberto; Marcaccio, M; Paolucci, F; Roffia, S.
abstract

The electrochemical multiple reduction of a series of polypyridinic compounds, yielding mono, di and trianionic species is theoretically studied. Calculated electron affinity values were used to obtain molecular-structure/reactivity relationships, the latter reflected by the experimental half-wave electroreduction potentials. Gas-phase electron affinity data vs. half-wave potentials produced satisfactory linear correlations, but separated for each successive electron transfer step (i.e. a linear relationship for the first electron transfer, yield of the monoanion, neatly separated from the one concerning the second electron transfer, yield of the dianionic species). The theoretical approach was pushed further, also including solvent effects. This was done by means of two methods based on the continuum solvation model: the Onsager cavity (SCRF) and the more sophisticated SM5.42R solvation models. In particular, the latter is able to group in a single correlation the potentials referring to the first, second and third electron transfer.

2002 - Electrochemistry and spectroelectrochemistry of ruthenium(II)-bipyridine building blocks. Different behaviour of the 2,3-and 2,5-bis(2-pyridyl)pyrazine bridging ligands [Articolo su rivista]
Marcaccio, M; Paolucci, F; Paradisi, C; Carano, M; Roffia, S; Fontanesi, Claudio; Yellowlees, Lj; Serroni, S; Campagna, S; Balzani, V.
abstract

We report the results of an investigation, using electrochemical and spectroelectrochemical techniques, into redox properties of uncoordinated free bis-chelating 2,3- and 2,5-bis(2-pyridyl)pyrazine ligands (2,3- and 2,5-dpp) and of the complexes of the [Ru(2,3-dpp)(n)(bpy)(3-n)](2+) and [Ru(2,5-dpp)(n)(bpy)(3-n)](2+) families (bpy = 2,2'-bipyridine), which are used as building blocks for obtaining polynuclear complexes. For comparison purposes, the electrochemical behaviour of the [Ru(2,3-dpp)(DCE-bpy)(2)](2+) complex, where DCE-bpy is 5.5'-dicarboxyethyl-2,2'-bipyridine, has also been investigated. Correlations of the E-1/2 values observed for the compounds examined (genetic diagrams) have allowed us to assign all the ligand-based reduction processes as well as to discuss electronic interactions. The localisation of the first three reduction processes for each complex has also been established on the basis of the spectroelectrochemical results. Theoretical calculations (AMI serniempirical and ab-initio level) carried out for the 2,5-dpp and 2,3-dpp ligands show that, in the uncoordinated state, the former ligand does not exhibit any substantial conformation arrangement, whereas the latter has a stable conformation for a large (56degrees) dihedral angle between the pyridyl and pyrazine rings. The changes in conformation upon mono- and bis-coordination of 2,3-dpp can account for its peculiar electrochemical behaviour consisting in a change of the number of redox processes with varying coordination state. (C) 2002 Elsevier Science B.V. All rights reserved.

2001 - Extensive redox series in dinuclear and dendritic Ru(II) complexes [Articolo su rivista]
Carano, M; Ceroni, P; Fontanesi, Claudio; Marcaccio, M; Paolucci, F; Paradisi, C; Roffia, S.
abstract

The electrochemical behavior of a dinuclear and a hexanuclear dendritic ruthenium(II) bipyridine complexes with 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) as bridging ligands has been investigated in highly purified liquid SO2 or N,N-dimethylformamide (DMF) solutions. The compounds have general formula [Ru-n(bpy)(n+2)(2,3-dpp)(n-1)](2n+), where n = 2 or 6; bpy is 2,2 ' -bipyridine. The wide anodic and cathodic potential windows explored in liquid SO2 and DMF, at low temperature, (up to ca. 4.3 and - 3.1 V vs. SCE, respectively) have allowed the observation of several metal-centered oxidations and ligand-centered oxidations and reductions, leading to the most extensive redox series so far reported, comprising up to 26 reversible ligand-centered reductions and 14 reversible metal- or ligand-centered oxidations, for a total of 40 redox processes in the hexanuclear complex. The redox standard potentials for overlapping processes in multielectron waves have been obtained from the analysis of the voltammetric curves and their digital simulation, and the localization of all the redox processes and an evaluation of the mutual interactions between the redox centers have been obtained. These results allowed to clarify the important role played by bridging ligands in mediating the interactions between the equivalent redox sites. Furthermore, the localization of the redox sites and the determination of relative standard potentials allowed the mapping of MLCT excited states within the dendrimeric structure, through the correlation between the absorption spectroscopic data and the relevant voltammetric data. (C) 2001 Elsevier Science Ltd. All rights reserved.

2001 - On the adsorption of pure ethylene glycol on mercury [Articolo su rivista]
Fontanesi, Claudio; Benedetti, L; Andreoli, Roberto; Carla, M.
abstract

The standard Gibbs energy of adsorption of pure liquid ethylene glycol (EG) on mercury is assessed to range between - 50 and - 60 kJ mol(-1) about two-three times with respect to water (- 21 kJ mol(-1)). This evidence is obtained on the basis of a series of indirect and independent experimental results. Moreover, ab-initio calculations are performed to account for the interaction energy relating the isolated EG molecule and a cluster of seven (or four) Hg atoms: three different geometrical approaches of the EG molecule with respect to the cluster are considered (top, hollow, bridge) as well as three EG conformations (trans, cis, cis-OH, the last one with an intramolecular hydrogen bond). The deepest minimum in the energy versus (Hg-cluster-EG(molecule)) distance potential energy curve, amounting to - 80 kJ mol(-1), is obtained in the case of the cis conformation of EG. In particular, it is found that this stabilizing energy is essentially due to the oxygen-mercury atoms interaction, giving rise also to an appreciable charge transfer coefficient from the EG molecule to the Hg duster. Finally, in this conformation, the EG adsorbed layer is also stabilized by an attractive energy term effective among vicinal interacting molecules. (C) 2001 Elsevier Science B.V. All rights reserved.

2001 - On the dissociation dynamics of the benzyl chloride radical anion. An ab initio dynamic reaction coordinate analysis study [Articolo su rivista]
Fontanesi, Claudio; Baraldi, Pietro; Marcaccio, M.
abstract

The dynamics of the dissociation of the benzyl chloride radical anion to a benzyl radical and chloride anion was studied theoretically. To this end two different conformations of benzyl chloride were examined: one featuring a 90 degrees angle between the Cl-C bond and the aromatic ring (conformation S), the other with the Cl-C bond and the aromatic moiety lying coplanar (conformation E). The potential-energy (PE) surface shows the existence of a conical intersection when studied as a function of the C-Cl bond length and of the rotation angle around the C(sp(2))-C(sp(3)) bond. Information on the dynamics of this process was obtained using the dynamic reaction coordinate (DRC) algorithm for tracing reaction paths. The DRC method shows a qualitative difference in the dissociation mechanism of the two conformers. The lifetime of conformation E depends on the amount of kinetic energy assigned to the internal rotational mode motion, whereas that of conformation S does not. (C) 2001 Elsevier Science B.V. All rights reserved.

2001 - On the kinetics of chromium electrodeposition on copper electrodes [Articolo su rivista]
Baraldi, Pietro; Soragni, Ercole; Fontanesi, Claudio; V., Ganzerli
abstract

In a previous work, we observed that, during cyclic potentiodynamic curves of cathodic polarisation (from 0.00 to - 1.25 V/SCE, 5 mV s(-1)) in chromic acid solution of industrial composition, ARMCO iron undergoes a pitting corrosion, while carbon steels undergo a selective ferritic corrosion. Blisters of pure iron were also observed on ARMCO iron electrodes surface. These occurrences suggest a direct participation of the metal substrate to the overall reaction of reduction of the chromic acid to chromium metal. Therefore, the chemical nature of the electrode metal has been changed, in order to pl avc that the chromium reduction goes on through an ECE mechanism involving a fast chemical reaction between unstable intermediate chromium reduction goes and the metal substrate. Cathodic potentiodynamic polarisation curves were performed on copper electrodes and the scans were stopped at four different potentials (-0.90, - 1.00, -1.10 and -1.25 V/SCE). The copper surface undergoes a severe corrosion in all the experimental conditions. The morphology of the attack depends on the polarisation potential and on the presence of additives in solution, like iron sulphate. (C) 2001 Elsevier Science B.V. All rights reserved.

2000 - Dynamic aspects of the electroreduction of chromic acid solutions [Articolo su rivista]
Soragni, E.; Fontanesi, C.; Barani, G.; Ganzerli, V.
abstract

Potentiodynamic and impedance spectroscopy measurements were performed on ARMCO iron, steels (C30, C40, C50), cast iron and graphite electrodes in a bath of industrial composition: CrO3 250 g dm-3, H2SO4 2.5 g dm-3. Attention focused on the electrochemical reactions occurring before the start of the chromium deposition. The electrochemical evidence is markedly affected by the chemical nature of the cathode. This is rationalized by proposing a reaction mechanism involving the formation, depending on the chemical nature of the substrate, of a passive adsorbed film consisting of mixed chromium and iron oxides. Moreover, the proposed overall scheme accounts for the presence of periodic current oscillations observed both in potentiodynamic and potentiostatic curves. In close agreement, impedance spectra show negative loops when measured at the corresponding potentials.

2000 - Electrochemistry of multicomponent systems: Redox series comprising up to 26 reversible reduction processes in polynuclear ruthenium(II) bipyridine-type complexes [Articolo su rivista]
Marcaccio, M.; Paolucci, F.; Paradisi, C.; Roffia, S.; Fontanesi, C.; Yellowlees, L. J.; Serroni, S.; Campagna, S.; Denti, G.; Balzani, V.
abstract

Electrochemical reduction of di-, tri-, tetra-, and hexanuclear complexes [Run(bpy)n+2(μ-2,X-dpp)n-1]2n+ (n = 2, 3, 4, 6; X = 3 or 5) has been studied and the reduction pattern established. It has been shown that these complexes are reduced in sequences of ligand-localized one-electron-transfer steps, organized in six multiplets of closely spaced reductions. Although the number of electron-transfer steps in each multiplet increases with increasing nuclearity, the general reduction pattern is the same for all the complexes investigated.

2000 - On the Frumkin interaction parameter in the adsorption of aromatics on mercury in ethylene glycol [Articolo su rivista]
Fontanesi, Claudio; L., Benedetti; Giovanardi, Roberto
abstract

The Frumkin interaction parameter (AF) for the adsorption of a small series of aromatic compounds on mercury from ethylene glycol (EG) is accounted for in value and mainly in sign (always positive) using the dispersion energy contribution (εd) due to the mutual interaction among adsorbing aromatics molecules and that regarding EG molecules leaving the surface. A successful result is anyway obtained when the change of conformation of EG from the cis one in the adsorbed state to the cis-OH in the bulk phase (i.e., a conformation featuring an intramolecular OH bond) is considered.

2000 - Study of the effect of intermediate reactive species, adsorbed at the metallic surface/aqueous solution interface, on the chromium electrodeposition dynamics [Articolo su rivista]
Baraldi, Pietro; G., Barani; Fontanesi, Claudio; Soragni, Ercole
abstract

The chemical and physical nature of the stages preceding the massive electrochemical reduction of chromium is studied combining electrochemical, scanning electron microscopy (SEM) and vibrational spectroscopy (IR) techniques. The collected evidence indicates that the formation of intermediate species occurs in the adsorbed phase. (C) 2000 Elsevier Science Ltd. All rights reserved.

1999 - Electrochemistry of multicomponent systems, redox series comprising up to 26 reversible reduction processes in polynuclear ruthenium(II) bipyridine-type complexes [Articolo su rivista]
Marcaccio, M; Paolucci, F; Paradisi, C; Roffia, S; Fontanesi, Claudio; Yellowlees, Lj; Serroni, S; Campagna, S; Denti, C; Balzani, V.
abstract

The electrochemical behavior of a family of polynuclear ruthenium(II) bipyridine-type complexes with 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) and 2,5-bis(2-pyridyl)pyrazine (2,5-dpp) as bridging ligands has been investigated in highly purified N,N-dimethylformamide solution. The compounds studied contain two, three, four, and six metal centers and have general formula [Ru-n(bpy)(n+2)(2,X-dpp)(n-l)](2n+), where n = 2, 3, 4, or 6, X = 3 or 5, and bpy is 2,2'-bipyridine, The wide cathodic potential window explored (up to ca. -3.1 V vs SCE) has allowed us to observe the most extensive ligand-centered odor series so far reported, comprising up to 26 reversible reduction processes for the hexanuclear complex. The redox standard potentials for overlapping processes in multielectron waves have been obtained from the analysis of the voltammetric curves and their digital simulation. The localization of each redox process and the mutual interactions of the redox centers have been elucidated through the analysis and comparison of the redox series of the various compounds. For the dinuclear species, the assignment of the redox sites has been confirmed by semiempirical molecular orbital calculations (ZINDO) and spectroelectrochemical experiments. Calculations also substantiate the important role played by bridging ligands in mediating the interactions between equivalent redox sites. Finally, it has been shown that the size of the supporting electrolyte cation has an influence on the processes occurring at the extreme cathodic region.

1998 - 2D phase transition of organic molecules adsorbed at the Hg electrode aqueous solution interface - Part 2 comparison of experimental data with model predictions [Articolo su rivista]
Fontanesi, Claudio
abstract

The 2D phase transition of thymine, uracil, guanine and coumarin, adsorbed at the Hg electrode/aqueous solution interface, is rationalised on the basis of the model proposed in Part 1, J. Chem. Sec., Faraday Trans., 1994, 90, 2925. The results together with that obtained for adenine, are compared with the relevant quantities calculated by using molecular descriptors (dipole moments and polarizabilities). Finally, a value of the standard eathalpy phase-transition variation, averaged over the results collected for the five compounds is estimated and discussed.

1998 - Characterisation of the surface conductivity of glassy materials by means of impedance spectroscopy measurements [Articolo su rivista]
Fontanesi, C.; Leonelli, C.; Manfredini, T.; Siligardi, C.; Pellacani, G. C.
abstract

Abstract The phenomenon of tin dioxide doping by antimony, Sb(V), atoms in semiconductive glazes is discussed. In particular, the impedance spectra of the glaze surface at room temperature were experimentally determined, and the results were analysed in terms of equivalent circuits. The parameters resulting from the fitting procedure were related to the SnO2/Sb(V) relative content, the SnO2/Sb (V) percentage in the glaze, and the microstructure as observed by SEM. It is proposed that the addition of SnO2 and Sb2O3 to a common glaze for ceramic tile results in a semiconductive continuous phase, whose electrical characteristics fulfil the antistatic floor regulation, as far as surface conductivity is concerned. As a whole the obtained results suggest that the thermal cycle used in fast firing technology is capable to promote the oxidation of Sb2O3 to Sb2O4, resulting in a sufficient amount of Sb(V) capable of generating a semiconductive behaviour of the SnO2 crystalline phase dispersed in the glaze. © 1998 Elsevier Science Limited. All rights reserved.

1998 - The comparative adsorption of aromatics on mercury from water and ethyleneglycol [Articolo su rivista]
Fontanesi, Claudio; Andreoli, Roberto; Benedetti, L.
abstract

The interfacial behaviour of benzaldehyde and p-methyl phenyl acetic acid in ethyleneglycol (EG), as well as that of o-dimethyltoluidine in water, has been investigated to obtain a number of adsorption parameters necessary to discuss the reliability, on a quantitative ground, of the intrinsic value of Gibbs adsorption energy; Delta G(int)degrees, relating, for a group of aromatic derivatives adsorbed on mercury, to the process: A(pure) + Hg reversible arrow Hg(A(adsorbed)). It has been shown that this quantity does not depend on the solvent in use, so that it is really intrinsic and can be usefully related to structural molecular parameters of the adsorbate alone, allowing the interfacial behaviour to be foreseen a priori. As a consequence the solvation in the adsorption state of the interfacial active species, either in EG and in water, can be considered to contribute little to the whole adsorption Gibbs energy. Eventually, EG itself shows an interfacial activity almost the double of that of water, similar to - 50 and similar to - 21 kJ mol(-1), respectively. So that, within this view the adsorption of aromatics from EG on mercury can be fully rationalized with respect their behaviour on Hg from water. (C) 1998 Elsevier Science Ltd. All rights reserved.

1997 - Aromaticity, electronic structure and molecular dimension in the adsorption of organic compounds on mercury - II. Intermolecular interactions among adsorbed molecules [Articolo su rivista]
Fontanesi, C.; Benedetti, L.
abstract

The Frumkin interaction parameter between aromatic molecules (neutral form) adsorbed from aqueous solution on mercury electrode, is related to the balance of energy dispersion terms (adsorbate-adsorbate) and water-water molecular interaction reflecting the role played by substitution on the electrode surface of water by the aromatic molecule. The interaction among adsorbed aromatics (in neutral form) is always attractive, so that the sign of αF (Frumkin parameter, positive or negative) arises from that kind of balance. For aromatic anions, taking into account a large partial charge transfer from the adsorbate to the metal surface, the change of ΔGADS0 at varying the coverage (θ) is mainly due to electrostatic repulsion among charge adsorbed particles. © 1997 Elsevier Science Ltd. All rights reserved.

1997 - Electrochemical processes involving a sulphonamide moiety [Articolo su rivista]
Borsari, Marco; Fontanesi, Claudio; Gavioli, Giovanna
abstract

The peculiar electrochemical and physico-chemical behaviour of RSO2 substituted compounds can be attributed to the electronwithdrawing effect induced by sulphur atom, in particular the acidity of the nitrogen-bound hydrogen and the presence of a characteristic electrochemical reduction mechanism. Adsorption process at the mercury-aqueous solution of benzenesulfonamide derivatives and RSO2N-protected aminoacids is investigated and explained using some calculated structural indexes. The relations among these indexes and the adsorption free energy indicate that substitutions on the amidic nitrogen greatly affect the interfacial behaviour. The comparison of the reduction process of RSO2 protected aminoacids with that of the sulphonamide derivatives in protic and aprotic solvents has shown that these aminoacids, in neutral form, can be better considered as sulfonamides and their electrochemical parameters fit structural correlations with theoretical indexes, as LUMO energy and localized charges, in the same way shown by sulfonamide derivatives. Using these correlations, the role of the RSO2 moiety on the amidic acidity and on the electron transfer process has been discussed also on the basis of the calculated differences in total energy of dissociated and undissociated species. Theoretical indexes allow to investigate the electron route in the electrochemical reduction and the role of the substituents on nitrogen atom in determining mechanism and energetics of the electrochemical process.

1997 - Reductive electron transfer on trichloromethyl derivatives of benzene and pyridine studied by electrochemical methods [Articolo su rivista]
Borsari, Marco; Dallari, D; Fontanesi, Claudio; Gavioli, Giovanna; Iarossi, Dario; Piva, R; Taddei, Ferdinando
abstract

The electrochemical reduction of alpha,alpha,alpha-trichlorotoluene (benzotrichloride) and of the corresponding isomeric pyridine derivatives has been investigated by cyclic voltammetry and microcoulometry. Three irreversible diffusion controlled reduction waves have been observed in the voltammetry of the trichloromethyl derivatives and are found to correspond to the progressive two-electron reduction of derivatives where a chlorine atom is substituted by a hydrogen atom. The peak potentials E-p show that reduction of the pyridine derivatives is easier than that of the benzene derivatives with the same number of chlorine atoms, the more positive shift occurring for the 4-substituted compounds. The experimental findings would indicate a concerted electron transfer-bond breaking (C-Cl) mechanism for all the compounds examined, as well as for the chloromethyl and dichloromethyl derivatives formed after Cl/H substitution. Electron uptake appears to be the rate-determining step of the reductive cleavage of these molecules. The effects of the different aromatic rings and of the degree of halogen substitution of the methyl group on the reduction potentials are discussed.

1997 - Theoretical study of the dissociative process of the 4-chlorotoluene radical anion [Articolo su rivista]
Fontanesi, Claudio
abstract

The dissociation of the 4-chlorotoluene radical anion, in the corresponding arylic open-shell and chloride closed-shell species, has been studied using semiempirical and ab initio methods, in both cases ROHF and UHF calculations have been performed. It is shown that semiempirical PESs are not reliable. While, at least a 3-21g basis set is needed to obtain an ab initio single determinant global dissociative path (which is qualitatively consistent with the experimental evidence). In addition, UMP2, ROMP2, SOCI dissociative PESs are discussed, suggesting that ROHF-based methods are preferable to UHF-based ones. This is shown to depend on the spin contamination affecting the UHF wavefunction.

1995 - ON THE NATURE OF THE NONANOIC ACID MONOLAYER ADSORBED AT THE HG/AQUEOUS SOLUTION INTERFACE - INFLUENCE OF CONFORMATIONAL FREEDOM IN BULK AQUEOUS-SOLUTION [Articolo su rivista]
Bordi, S; Carla, M; Passamonti, P; Fontanesi, Claudio; Pelloni, P.
abstract

The adsorption of the nonanoic acid at the electrified Hg/aqueous solution interface is studied by means of capacity and surface tension measurements. Comparison of the experimental Gamma(max) value with the calculated more favoured solvated conformation suggests that the acid is adsorbed in a partially coiled conformation. The adsorption free energy here determined, together with previously reported values found in the literature concerning other saturated acids and alcohols, is compared with reactivity and calculated molecular descriptors. The collected evidence suggests that the hydrophobic nature of the acid is responsible for the adsorption, while the electric field/molecule interaction, occurring at the electrified interface, governs the desorption. Lastly, some experimental (capacitive transients, effect of the temperature on the tensammetric curves) and theoretical findings are discussed which indicate that the adsorbed acid monolayer should be regarded as a usual, in the field of adsorption at electrodes, disordered network. Thus excluding the occurrence of a two-dimensional phase transition involving the formation of a 2D solid-like film.

1994 - AROMATICITY, ELECTRONIC-STRUCTURE AND MOLECULAR DIMENSION IN THE ADSORPTION OF ORGANIC-COMPOUNDS ON MERCURY .1. THE METAL ADSORBATE INTERACTION [Articolo su rivista]
Benedetti, L; Fontanesi, Claudio
abstract

The adsorbability of a wide series of aromatic derivatives (38) on mercury from aqueous solution at constant potential (E(pzc) or close to it) cannot be simply accounted for by the '' aromaticity '' of the compounds, at any rate modulated by substituent groups on the aromatic moiety, even if the adsorbates show a common planar disposition on the surface in the adsorbed state. The interfacial activity can be successfully related to the process of formation of a ''soft-soft'' couple (in the Pearson's concept) between mercury and the organic, in competition with the 'hard-soft'' couple between the metal and water. Desorption is then explained with a higher 'hard'' character of mercury at increasing negative potential. In this view, the feasibility of a partial charge transfer, as expressed by lambda, calculated for neutral organic adsorbates, corresponding to a positive DELTAN value (DELTAN, fractional number of electrons transferred from the adsorbate to the mercury) can be confirmed. A simple relation between adsorbability and ''bulkyness'' of the compounds, in relation to the dislodgement of water molecules from the surface occurring in the adsorption process is proposed and discussed.

1994 - ELECTROCHEMICAL REDUCTION OF BENZAMIDE AND THEIR O-HALO-DERIVATIVES AND P-HALO-DERIVATIVES IN NONAQUEOUS SOLVENTS [Articolo su rivista]
Benedetti, Luca; Borsari, Marco; Dallari, D; Fontanesi, Claudio; Grandi, G; Gavioli, Giovanna
abstract

The analysis of the polarographic, voltammetric and coulometric results shows that the overall reduction mechanism of benzamide occurs with the cleavage of the C-N bond. However, the first step of the electrochemical process leads to the formation of a radical anion which undergoes protonation by another benzamide molecule in DMF and DMSO or by the solvent in CH3CN and C2H5OH. Theoretical calculations have been performed to clarify the mechanism. Halobenzamide reduction involves the C-halogen bond breaking as the first reduction step to give benzamide.

1994 - ENTROPY CHANGE IN THE 2-DIMENSIONAL PHASE-TRANSITION OF ADENINE ADSORBED AT THE HG ELECTRODE AQUEOUS-SOLUTION INTERFACE [Articolo su rivista]
Fontanesi, Claudio
abstract

The combined effect of temperature, bulk concentration and applied potential, on the stability of the condensed phase of adenine adsorbed at the mercury/aqueous solution interface, is rationalized assuming that the occurrence of a 2D phase transition involves only two distinct adsorbed phases. The chemical potential, mu, which drives the equilibrium at the phase transition, is expressed by means of an equation which accounts explicitly for the electric field-adsorbed molecule interaction. The approach enables the standard entropy variation of the overall process to be determined. The findings are consistent with the ordered nature of the adsorbed phase, with which the appearance of a low and constant capacity region in the capacity vs. potential curves is associated. The standard entropy variation for the 2D 'flat --> perpendicular (solid-like)' phase transition is estimated and discussed.

1994 - Theoretical study of the electroreduction of halogenated aromatic compounds. Part 3. - O-, m- and p-dibromobenzenes studied by AM1 and PM3 methods [Articolo su rivista]
Andreoli, Roberto; Gavioli, Giovanna; Borsari, Marco; Fontanesi, Claudio
abstract

The electroreductive potential values of the o-, m- and p-dibromobenzenes (DBBs) follow an unusual pattern in that, unlike the structurally related dichlorobenzene (DCB) derivatives, these three isomers exhibit a strong 'ortho effect' and are accompanied by a large difference in the E1/2 values. Any interference with the mechanism of reduction on the part of the chemical environment can be safely ruled out, given the consistency of the E1/2 values obtained in four different solvents. The use of theoretical indices calculated by the PM3 method enables the experimental behaviour of the DBBs to be rationalised on the basis of the electronic structure of the neutral isolated molecule. Remarkably, PM3 indicates the formation of a sigma-type radical anion in the case of the reduction of the bromobenzene derivatives.

1993 - THEORETICAL-STUDY OF THE ELECTROREDUCTION OF HALOGENATED AROMATIC-COMPOUNDS .2. BROMINE AND CHLORINE DERIVATIVES IN DIFFERENT ORGANIC-SOLVENTS [Articolo su rivista]
Gavioli, Giovanna; Borsari, Marco; Fontanesi, Claudio
abstract

The electrochemical dehalogenation of a variety of halogenated aromatic compounds is studied by means of semiempirical (AM1) and ab initio (ROHF 3-21G*) calculations. Comparison of the electrochemical half-wave potential values (E1/2) and calculated theoretical indices indicates the formation of a pi radical following the electron uptake. Moreover, the relationship observed between the half-wave potential, in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and the electron affinity suggests that the reduction potential is determined by the first electron uptake and that kinetic factors play a minor role, their influence being constant or negligible.

1992 - 2D phase transition of Benzoic acid at the Hg/aqueous solution interface [Articolo su rivista]
Fontanesi, Claudio
abstract

The electroadsorptive behaviour of benzoic acid, investigated by means of a.c. phase selective polarography under different experimental conditions (1 mol dm–3 NaClO4, 1 mol dm–3 NaCl), shows a marked dependence on the temperature, indicating the existence of a two-dimensional phase transition gas-like(disordered disposition of the adsorbed molecules)solid-like(ordered disposition of the adsorbed molecules). The experimental results in terms of the variation induced by different temperatures on the capacity vs. potential curves are analysed, leading to the determination of a repulsive intermolecular energy, in contrast with the experimental evidence presented and with previously obtained data concerning the Frumkin interaction factor. Values of ?AA that are attractive are calculated by the atom–atom potential method, thus supporting theoretically the experimental evidence for condensation of the adsorbed benzoic acid molecules.

1992 - ELECTROSORPTION OF HARD AND SOFT AROMATIC DERIVATIVES ON MERCURY [Articolo su rivista]
Benedetti, L; Gavioli, Gb; Fontanesi, Claudio
abstract

An 'intrinsic' value of the adsorption Gibbs energy (DELTA-G(int)-degrees) parallel-to, not directly proportional to the measured DELTA-G(ads) parallel-to, has been evaluated for a set of 28 aromatic, heterocyclic and naphthalenic derivatives. The structural feature of (DELTA-G(int)-degrees) parallel-to is rationalised in terms of a 'soft' interaction with mercury at the point of zero change, on the basis of the Parr and Pearson concept, accounting on a quantitative basis for the different adsorbability of the compounds. Moreover, the partial charge-transfer coefficient, lambda, has been related in a satisfactory way to DELTA-N (the fractional number of electrons transferred) calculated taking into account the absolute electronegativity, chi, and the hardness, eta, both of the adsorbate and of mercury.

1991 - Electrochemical behaviour of oxaziridines at the mercury electrode in organic solvent [Articolo su rivista]
Torre, Giovanni; Moretti, I; Forni, Arrigo; Grandi, G; Fontanesi, Claudio; Borsari, Marco; Gavioli, Gb
abstract

The electrochemical behaviour of 2-methylsulphonyl-3-phenyloxaziridine (1) and 2-t-butyl-3-phenyloxaziridine (2) has been investigated by polarograhic techniques in aprotic solvent. The electroreductive center appears to be the oxaziridine ring but the rearrangement following the electron uptake yields benzaldehyde and imine for the derivatives (1) and (2) respectively. This peculiar behaviour has been discussed on the basis of calculated theoretical indices (CNDO/2 method), like energy values and shapes of frontier molecular orbitals, which suggest the N-O bond breaking as the first step of the overall reduction process.

1990 - A THEORETICAL AND TOPOLOGICAL STUDY ON THE ELECTROREDUCTION OF CHLOROBENZENE DERIVATIVES [Articolo su rivista]
Benedetti, L; Gavioli, Gb; Fontanesi, Claudio
abstract

1990 - Anodic behaviour of the mercury electrode in aqueous solution of 1,10-phenanthroline. The role of adsorption and nucleation processes [Articolo su rivista]
Andreoli, Roberto; Gavioli, Gb; Benedetti, L; Borsari, Marco; Fontanesi, Claudio
abstract

The anodic dissolution of the mercury electrode in 1,10-phenanthroline (phen) aqueous solution has been investigated by polarographic and voltammetric methods. The adsorption processes affecting the entire mechanism of oxidation and the complex formation have been observed and analysed introducing the random adsorption model (Frumkin isotherm) and the nucleation-growth collision model. The results suggest the occurrence of different surface structures of phenanthroline itself (the ligand) as well as of the product of the oxidative process, [Hg(phen)2]2+, upon varying the ligand concentration in the bulk. © 1990.

1990 - KINETICS OF COMPACT LAYER FORMATION AND GROWTH OF 1,10-PHENANTHROLINE AT THE ELECTRODE SURFACE [Articolo su rivista]
Benedetti, Luca; Borsari, Marco; Fontanesi, Claudio; Gavioli, Giovanna
abstract

KINETICS OF COMPACT LAYER FORMATION AND GROWTH OF 1,10-PHENANTHROLINE AT THE ELECTRODE SURFACE WERE INVESTIGATED

1990 - Phase transition in the adsorption process of N-Dansylglycinate anion on Mercury [Articolo su rivista]
Benedetti, Luca; Borsari, Marco; Gavioli, Giovanna; Fontanesi, Claudio
abstract

PHASE-TRANSITION IN THE ADSORPTION PROCESS OF N-DANSYLGLYCINATE ANION ON MERCURY WAS STUDIED

1989 - Electrochemical behaviour of N-Tosylglycine and N-Dansylglycine in several solvents. The role of the RSO2- groups on the physico-chemical properties of Glycine [Articolo su rivista]
Fontanesi, Claudio; Borsari, Marco; Andreoli, A.; Benedetti, L.; Grandi, G.; Gavioli, G.
abstract

The comparison of the electrochemical behaviour of N-tosylglycinoa nd N-dansylglycinew withthat of the corresponding amides and the benzenesulphonamidine in protic and aprotic media has shown thatthe RSO2- protected aminoacids, in their neutral form, can be considered as benzenesulphonamidederivatives and their E1/2 values fit the structural correlations among experimental and theoreticalparameters already discussed in previous papers. Using these correlations, the role of the RSO2- andcarboxylate groups on the amidic acidity of the free and complexed aminoacid has been determined also onthe basis of calculated differences in total energy of dissociated and undissociated acidic species. Allthese results confirm the main role played by the carboxylate group on the formation of N-O bidentatecomplexes.

1989 - The effect of lateral chains on the electrochemical and physico-chemical behaviour of Tosyl-N-protected aminoacids [Articolo su rivista]
Benedetti, Luca; Borsari, Marco; Fontanesi, Claudio; Grandi, Giulia; Andreoli, Roberto
abstract

The electrochemical behaviour in protic and aprotic solvents of some tosylaminoacids bearing a lateral electroinactive chain confirms that the reduction mechanism conforms to that one already proposed for tosyl- and dansylglycine and benzenesulphonamide derivatives. The E value reveals to be a good structural index and relationships between empirical and calculated structural parameters show that the presence of the carboxylate group in tosylaminoacids causes an increase of NH bond acidity with respect to benzenesulphonamide derivatives. The pK values of the amide group are influenced by the kind of the lateral chains and by the position of carboxylic group in the molecular frame.

1988 - Electrochemical behaviour of Chlorobenzene sulphonamide derivatives at the Mercury electrode in non aqueous solvents [Articolo su rivista]
Borsari, Marco; Fontanesi, Claudio; Andreoli, R.; Benedetti, L.; Gavioli, G.
abstract

The analysis of polarographic and coulometric results shows that the overall reductionmechanism of chlorobenzenesulphonamide derivatives occurs with the cleavage of the C-Cl bond followed bythe reduction of the benzenesulphonamide involving the S-N bond breaking. However, theg, ,2 values fit thestructural relation E, ,2-ELUMo for the series of benzenesulphonamides and not that of the chlorobenzenederivatives and the shape of the LUMO of chlorobenzenesulphonamides is similar to that of thebenzenesulphonamide, so that it is sensible to suggest that the first step of the reduction mechanism is thesame for all the benzenesulphonamide derivatives and involves the C-S-N moiety of the molecules.

1988 - Molecular structure-interfacial activity relation\-ship of N-substituted aminoacids, adsorption of N-Dansylglycine at the Mercury/aqueous solution interface [Articolo su rivista]
Andreoli, R.; Barbieri, A.; Benedetti, L.; Fontanesi, Claudio; Gavioli, G.
abstract

The adsorption of N-dansylglycine (5-dimethylaminonaphthalene-I-sulphanylglycine) in monoaniomcand dianionic forms has been characterized in aqueous solution at a mercury electrode. At pH 6(only the monoanionic form present in the bulk), N-dansylglycine is arranged on the metal surface m aperpendicular manner through the naphthyl moiety, and an attractive interaction factor among theadsorbed molecules is observed. At pH 12 (dianionic form), the molecules is still arranged in a perpendicularway show a greater molecular area and no interaction factor is revealed. These features. together withthose regarding a series of other N-substituted glycine derivatives previously studied, are related to somecalculated structural indices, and a relationship is obtained between the adsorption Gibbs energy andAE, n (the energy difference between the lowest unoccupied molecular orbital and the highest occupiedone). Moreover, some local theoretical indices (net atomic charges, partial net charges) are used in atentative molecular interpretation of the disposition of the sorbate on the surface and of the significanceof the Frumkin interaction factor. To offer a more general grounding to the argument, a group ofnaphthyl and benzoyl denvatives studied by Bockris and co-workers (J. Phys. Chem., 65 (1961) 2000) invery similar conditions is also considered.

1986 - Adsorption of N-Acetyl and N-Benzoyl Glycine at the Mercury/aqueous solution interface. [Articolo su rivista]
Fontanesi, Claudio; Gavioli, G.; Andreoli, R.; Benedetti, L.
abstract

In previous papers the electrochemical behaviour of complexes of someamino acids with metal ions in aqueous and non-aqueous solutions was investigated.Since there is considerable interest in the behaviour of amino acids at the electrodeinterface, mainly with regard to the possibility of establishing relationships betweenmolecular properties and adsorption parameters, we deal, in this study, withthe interfacial behaviour of N-acetylglycine (aceturic acid) and N-benzoylglycine(hippuric acid) at the mercury-aqueous solution interface (0.1 A4 NaClO., + NaOH,pH 12).