| Abstract
| - The electronic structure of binuclear diruthenium tetracarboxylates, in both the divalent Ru2II,II(O2CR)4 and themixed-valent Ru2II,III(O2CR)4X (X = anion) states is studied by means of ZINDO/S-MRCI and DFT calculations.Both methods predict a (π*)2(δ*)2 ground-state configuration for the divalent species, contrary to the (π*)3(δ*)1previously predicted by SCF-Xα calculations, but in agreement with magnetic measurements that show a strongZero Field Splitting. Our ZINDO/S-MRCI calculations on compounds containing axial ligands with differentdegree of π bonding to the bimetallic center (water, chloride, carboxylate, pyridine, pyrazine), for both (II,II) and(II,III) ruthenium cores, show the important role played by the ligands. These theoretical calculations allow us toexplain the differences observed in the UV/vis and resonance Raman spectra, both in solution and in the solidstate, when varying the axial ligands. The ZINDO/S-MRCI calculations are also capable of solving somecontroversies found in the literature, related to the assignment of the main electronic bands for both kinds ofcompounds. The electronic structures predicted by the DFT methodology are in agreement with both theexperimental evidence and the ZINDO/S calculations. Moreover, our DFT calculations provide an interpretationof the intermolecular magnetic interactions in the mixed-valent species, explaining the dependence of theantiferromagnetic coupling on the intermolecular Ru−X−Ru angle.
- ZINDO/S-CI and DFT calculations predict a (π*)2(δ*)2 ground state configuration for divalent Ru2II,II(O2CR)4L2 compounds, and (π*)2(δ*)1 configuration for mixed-valent [Ru2II,III(O2CR)4L2]+/- analogues. The solution and solid state spectroscopic properties (UV/vis, RR) and magnetic behaviour of both kind of compounds are interpreted on the basis of these calculations, solving controversies found in the literature related to the assignment of their electronic bands and ground state configurations. The influence of the axial ligands on these properties is assessed.
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