Publications (30) View all
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Article: Experimental and Theoretical Study of the n-Doped Successive Polyanions of Oligocruciform Molecular Wires: Up to Five Units of Charge.
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ABSTRACT: The electronic structure of polyanions of sterically encumbered triisopropylsilyl-substituted linear and cyclic oligo(phenyleneethynylene)s (Monomer, Trimer, Pentamer, and Triangle) is investigated by electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and UV/Vis-near-infrared (NIR) spectroscopies, cyclic voltammetry, and theoretical calculations (DFT). Increasing anion orders are generated sequentially in vacuo at room temperature by chemical reaction with potassium metal up to the pentaanion. The relevance of these compounds acting as electron reservoirs is thus demonstrated. Even-order anions are EPR silent, whereas the odd species exhibit different signatures, which are identified after comparison of the measured hyperfine couplings by ENDOR spectroscopy with those predicted by DFT calculations. With increasing size of the oligomers the electron spin density is first distributed over the backbone carbon atoms for the monoanions, and then further localized at the outer phenyl rings for the trianion species. Examination of the UV/Vis-NIR spectra indicates that the monoanions (T(.) (-) , P(.) (-) ) exhibit two transitions in the Vis-NIR region, whereas a strong absorption in the IR region is solely observed for higher reduced states. Electronic transitions of the neutral monoanions and trianions are redshifted with increasing oligomer size, whereas for a given oligomer a blueshift is observed upon increasing the charge, which suggests a localization of the spin density.ChemPhysChem 02/2013; · 3.41 Impact Factor -
Article: Structural, magnetic and optical properties of an Fe(III) dimer bridged by the meridional planar divergent N,N'-bis(salicyl)hydrazide and its photo- and electro-chemistry in solution.
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ABSTRACT: {Fe(III)Cl(DMF)(2)}(2)(L) where L is N,N'-bis(salicyl)hydrazide has been synthesized as red crystals and characterized using single-crystal diffraction, infrared and UV-vis spectroscopies, and its magnetic properties studied. The dimeric unit in the structure is formed through the two meridional sets of divergent O, N, O coordinating atoms of the hexacoordinated and quadruply charged ligand. With the presence of the inversion symmetry the Fe atoms are strictly planar with the ligand. The magnetic exchange interaction is found to be antiferromagnetic with a J = -5.98(3) cm(-1) through the rare Fe-N-N-Fe pathway. Irradiation of the FeCl(3)/H(4) red DMF solution in the visible region of the spectrum resulted in its complete discoloration and from which the unknown colorless salt [Fe(II)(DMF)(6)][Fe(II)Cl(4)] and the neutral ligand have been identified by single crystal diffraction. The UV-visible spectra of FeCl(3), H(4) and their mixture in DMF solution indicate that the iron complex is the absorbing species and the presence of the free ligand in the irradiated solution suggests that the ligand is potentially acting as a catalyst to the photoreduction of Fe(III) to Fe(II), while electrochemistry points to a mixed-valent (Fe(II)-Fe(III)) intermediate in the process.Dalton Transactions 11/2012; · 3.84 Impact Factor -
Article: Modulation of self-assembly and magnetism of Cu(II) grids in solution.
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ABSTRACT: Depending on the Cu(II)/ligand molar ratio, a pyrimidine-based ligand generates a tetranuclear grid (1/1) or a dinuclear stick (2/1). EPR, MS and visible spectroscopy studies suggest that dilution produces partial dissociation of the grid in solution. Replacement of 2-H-pyrimidine by a 2-phenyl-triazine unit prevents the dissociation of the grid. All these factors influence the magnetic properties of the architectures herein involved.Chemical Communications 09/2011; 47(39):10951-3. · 6.17 Impact Factor -
Article: Diporphyrinylamines: synthesis and electrochemistry.
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ABSTRACT: The synthesis of three possible diporphyrinylamines is described. All compounds were obtained by using the Buchwald-Hartwig aromatic amination reaction. The electronic spectra of the three porphyrin dimers showed characteristic features found in highly delocalized systems. The first oxidation of these compounds took place on the connecting amine function.Organic Letters 08/2011; 13(17):4742-5. · 5.86 Impact Factor -
Article: Novel Cr(III) dinuclear complexes supported by salicyloylhydrazono dithiolane and dithiane ligands: synthesis, stability, crystal structures and magnetic properties.
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ABSTRACT: We hereby report the synthesis, crystal structures and magnetic characterizations of three novel Cr(III) complexes: a mononuclear Cr(III)(HL((1)))₃ species along with two dinuclear μ-methoxo Cr(III)₂(μ-OMe)₂(HL)₄ (H₂L((1)): 2-salicyloylhydrazono-1,3-dithiolane; H₂L((2)): 2-salicyloylhydrazono-1,3-dithiane). EPR studies indicate that both dinuclear complexes (2a and 2b) are stable in solution (CHCl₃). Both Cr(III) dinuclear complexes exhibit a strong antiferromagnetic coupling. DFT calculations performed for complex 2a are in agreement with a strong antiferromagnetic exchange interaction in these new dinuclear Cr(III) complexes.Dalton Transactions 04/2010; 39(19):4579-85. · 3.84 Impact Factor
