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Maria Jesus RODRIGUEZ DOUTON

Personale tecnico amministrativo
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2021 - Electrostatic Control of the Thermoelectric Figure of Merit in Ion-Gated Nanotransistors [Articolo su rivista]
Prete, D.; Dimaggio, E.; Demontis, V.; Zannier, V.; Rodriguez-Douton, M. J.; Guazzelli, L.; Beltram, F.; Sorba, L.; Pennelli, G.; Rossella, F.
abstract

Semiconductor nanostructures have raised much hope for the implementation of high-performance thermoelectric generators. Indeed, they are expected to make available reduced thermal conductivity without a heavy trade-off on electrical conductivity, a key requirement to optimize the thermoelectric figure of merit. Here, a novel nanodevice architecture is presented in which ionic liquids are employed as thermally-insulating gate dielectrics. These devices allow the field-effect control of electrical transport in suspended semiconducting nanowires in which thermal conductivity can be simultaneously measured using an all-electrical setup. The resulting experimental data on electrical and thermal transport properties taken on individual nanodevices can be combined to extract ZT, guide device optimization and dynamical tuning of the thermoelectric properties.

2020 - Publisher Correction: Fe-functionalized paramagnetic sporopollenin from pollen grains: one-pot synthesis using ionic liquids (Scientific Reports, (2020), 10, 1, (12005), 10.1038/s41598-020-68875-6) [Articolo su rivista]
Chiappe, C.; Rodriguez-Douton, M. J.; Mozzati, M. C.; Prete, D.; Griesi, A.; Guazzelli, L.; Gemmi, M.; Caporali, S.; Calisi, N.; Pomelli, C. S.; Rossella, F.
abstract

In the original version of this Article, F. Rossella was incorrectly listed as a corresponding author. The correct corresponding author for this Article is C.S. Pomelli. Correspondence and request for materials should be addressed to christian.pomelli@unipi.it. This error has now been corrected in the HTML and PDF versions of the Article.

2020 - S-functionalized tripods with monomethylene spacers: Routes to tetrairon(III) single-molecule magnets with ultrashort tethering groups [Articolo su rivista]
Cornia, A.; Danieli, C.; Meglioli, F.; Tancini, E.; Nicolini, A.; Rodriguez-Douton, M. J.; Barra, A. -L.; Affronte, M.; Sessoli, R.
abstract

The organization of single-molecule magnets (SMMs) on surfaces is a mainstream research path in molecular magnetism. Of special importance is the control of grafting geometry in chemisorbed monolayers on metal surfaces. We herein present the synthesis, solid-state structure, and magnetic characterization of propeller-like tetrairon(III) SMMs containing the shortest-reported tethering groups for gold surfaces. Functionalization of molecular structure is attained using 2-R-2-(hydroxymethyl)propane-1,3-diol tripodal proligands (H3LR). The R substituents comprise a monomethylene spacer and three different terminations known to act as stable precursors of S-Au bonds (R = CH2SCN, CH2SAc and CH2SSnBu). These chemical groups are shown to be chemically compatible with the tetrairon(III) core and to afford fully-functional SMMs in crystalline form and in fair to excellent yields.

2012 - Magnetic Bistability of Isolated Giant-Spin Centers in a Diamagnetic Crystalline Matrix [Articolo su rivista]
L., Vergnani; A. L., Barra; P., Neugebauer; RODRIGUEZ DOUTON, Maria Jesus; R., Sessoli; L., Sorace; W., Wernsdorfer; Cornia, Andrea
abstract

Polynuclear single-molecule magnets (SMMs) were diluted in a diamagnetic crystal lattice to afford arrays of independent and iso-oriented magnetic units. Crystalline solid solutions of an Fe4 SMM and its Ga4 analogue were prepared with no metal scrambling for Fe4 molar fractions x down to 0.01. According to high-frequency EPR and magnetic measurements, the guest SMM species have the same total spin (S = 5), anisotropy, and high-temperature spin dynamics found in the pure Fe4 phase. However, suppression of intermolecular magnetic interactions affects magnetic relaxation at low temperature (40 mK), where quantum tunneling (QT) of the magnetization dominates. When a magnetic field is applied along the easy magnetic axis, both pure and diluted (x = 0.01) phases display pronounced steps at evenly spaced field values in their hysteresis loops due to resonant QT. The pure Fe4 phase exhibits additional steps which are firmly ascribed to two-molecule QT transitions. Studies on the field-dependent relaxation rate showed that the zero-field resonance sharpens by a factor of five and shifts from about 8 mT to exactly zero field on dilution, in agreement with the calculated variation of dipolar interactions. The tunneling efficiency also changes significantly as a function of Fe4 concentration: the zero-field resonance is significantly enhanced on dilution, while tunneling at +-0.45 T becomes less efficient. These changes were rationalized on the basis of a dipolar shuffling mechanism and transverse dipolar fields, whose effect was analyzed by using a multispin model. Our findings directly prove the impact of intermolecular magnetic couplings on SMM behavior and disclose the magnetic response of truly isolated giant spins in a diamagnetic crystalline environment.

2012 - Magnetic and Optical Bistability in Tetrairon(III) Single Molecule Magnets Functionalized with Azobenzene Groups [Articolo su rivista]
T. K., Prasad; G., Poneti; L., Sorace; RODRIGUEZ DOUTON, Maria Jesus; A. L., Barra; P., Neugebauer; Costantino, Luca; R., Sessoli; Cornia, Andrea
abstract

Tetrairon(III) complexes known as “ferric stars” have been functionalized with azobenzene groups to investigate the effect of light-induced trans–cis isomerization on single-molecule magnet (SMM) behaviour. According to DC magnetic data and EPR spectroscopy, clusters dispersed in polystyrene (4% w/w) exhibit the same spin (S = 5) and magnetic anisotropy as bulk samples. Ligand photoisomerization, achieved by irradiation at 365 nm, has no detectable influence on static magnetic properties. However, it induces a small but significant acceleration of magnetic relaxation as probed by AC susceptometry. The pristine behaviour can be almost quantitatively recovered by irradiation with white light. Our studies demonstrate that magnetic and optical bistability can be made to coexist in SMM materials, which are of current interest in molecular spintronics.

2011 - A Novel Tripodal Ligand with Organosulfur Alligator Clips for Deposition of Tetrairon(III) Single Molecule Magnets on Gold [Articolo su rivista]
RODRIGUEZ DOUTON, Maria Jesus; R., Sessoli; Cornia, Andrea
abstract

A propeller-like tetrairon(III) complex functionalized with two 1,2-dithiolan-3-yl groups was synthesized and magnetically characterized. The compound has formula [Fe4(thioctic)2(dpm)6] and was specifically designed to be grafted on gold surfaces. It was prepared by reacting [Fe4(OMe)6(dpm)6] (Hdpm = dipivaloylmethane) with a new tripodal ligand, H3thioctic, obtained by esterification of 2,2-bis(hydroxymethyl)-propane-1,3-diol with (±)-alpha-lipoic acid (also known as thioctic acid). Direct current and alternating current magnetic measurements revealed single-molecule magnet behaviour with an effective anisotropy barrier of 14.0(1) K resulting from a high spin (S = 5) ground state and an easy-axis anisotropy.

2011 - One-step Covalent Grafting of Fe4 Single-Molecule Magnet Monolayers on Gold [Articolo su rivista]
RODRIGUEZ DOUTON, Maria Jesus; M., Mannini; L., Armelao; A. L., Barra; TANCINI, ERIK; R., Sessoli; CORNIA, Andrea
abstract

Iron(III)-based single-molecule magnets have been covalently grafted on Au(111) in one step using 1,2-dithiolan-3-yl side groups. Reaction with the substrate quantitatively affords a monolayer of electronically intact clusters doubly linked to the surface via Au–S bonds, as demonstrated by a combination of STM, XAS/XMCD and XPS studies.

2010 - Introduction of Ester and Amido Functions in Tetrairon(III) Single-Molecule Magnets: Synthesis and Physical Characterization [Articolo su rivista]
Rodriguez Douton, Maria Jesus; Cornia, Andrea; R., Sessoli; L., Sorace; A. L., Barra
abstract

Tetrairon(III) complexes with a propeller-like structure derived from [Fe4(OMe)6(dpm)6] (1) (Hdpm = 2,2,6,6-tetramethylheptane-3,5-dione) are providing a growing class of Single Molecule Magnets (SMMs) displaying unprecedented synthetic flexibility and ease of functionalization. Herein we report the synthesis, crystal structures and magnetic properties of two novel tetrairon(III) SMMs, [Fe4(esterC5)2(dpm)6] (2) and [Fe4(amideC5)2(dpm)6]·Et2O·4MeOH (3·Et2O·4MeOH), in whichfunctionalization of the cluster core is achieved using ester and amido linkages, respectively. To this aim, two new tripodal ligands were prepared by acylation of pentaerythritol (2,2-bis(hydroxymethyl)-propane-1,3-diol) and TRIS (2-amino-2-(hydroxymethyl)propane-1,3-diol), namely H3esterC5 =RC(O)OCH2C(CH2OH)3 and H3amideC5 = RC(O)NHC(CH2OH)3 with R = n-butyl. The compounds were structurally investigated by single-crystal XRD, which demonstrated coordination of the tripodal ligands to the cluster core. The products display SMM behavior with anisotropy barriers Ueff/kB~=11 Kdue to a high-spin (S = 5) ground state and an easy axis anisotropy, described by D = -0.421 cm-1 in 2and -0.414 cm-1 in 3·Et2O·4MeOH. The departure of Ueff from the total splitting of the S = 5 ground multiplet, U/kB~=15 K, has to be ascribed to the sizeable rhombic anisotropy that characterizes the two compounds (E = 0.021 cm-1 in 2 and 0.019 cm-1 in 3·Et2O·4MeOH), as confirmed by master matrixcalculations of the temperature-dependent relaxation time.

2010 - Slow Magnetic Relaxation from Hard-axis Metal Ions in Tetranuclear Single-Molecule Magnets [Articolo su rivista]
Tancini, Erik; RODRIGUEZ DOUTON, Maria Jesus; L., Sorace; A. L., Barra; R., Sessoli; Cornia, Andrea
abstract

We report the synthesis of the novel heterometallic complex [Fe3Cr(L)2(dpm)6]⋅Et2O (Fe3CrPh) (Hdpm=dipivaloylmethane, H3L=2-hydroxymethyl-2-phenylpropane-1,3-diol), obtained by replacing the central iron(III) atom by a chromium(III) ion in an Fe4 propeller-like single-molecule magnet (SMM). Structural and analytical data, high-frequency EPR (HF-EPR) and magnetic studies indicate that the compound is a solid solution of chromium-centred Fe3Cr (S=6) and Fe4 (S=5) species in an 84:16 ratio. Although SMM behaviour is retained, the |D| parameter is considerably reduced as compared with the corresponding tetra-iron(III) propeller (D=−0.179 vs. −0.418 cm−1), and results in a lower energy barrier for magnetisation reversal (Ueff/kB=7.0 vs. 15.6 K). The origin of magnetic anisotropy in Fe3CrPh has been fully elucidated by preparing its Cr- and Fe-doped Ga4 analogues, which contain chromium(III) in the central position (c) and iron(III) in two magnetically distinct peripheral sites (p1 and p2). According to HF-EPR spectra, the Cr and Fe dopants have hard-axis anisotropies with Dc=0.470(5) cm−1, Ec=0.029(1) cm−1, Dp1=0.710(5) cm−1, Ep1=0.077(3) cm−1, Dp2=0.602(5) cm−1, and Ep2=0.101(3) cm−1. Inspection of projection coefficients shows that contributions from dipolar interactions and from the central chromium(III) ion cancel out almost exactly. As a consequence, the easy-axis anisotropy of Fe3CrPh is entirely due to the peripheral, hard-axis-type iron(III) ions, the anisotropy tensors of which are necessarily orthogonal to the threefold molecular axis. A similar contribution from peripheral ions is expected to rule the magnetic anisotropy in the tetra-iron(III) complexes currently under investigation in the field of molecular spintronics.