Theoretical and experimental studies of diruthenium tetracarboxylates structure, spectroscopy, and electrochemistry

Quantum mechanical calculations at the density functional theory (DFT) level have been performed on diruthenium tetracarboxylates of different levels of molecular complexity: from unsolvated monomers to oligomers. The agreement between the calculated and experimental molecular structures and vibrational modes of the simple [Ru2(micro-O2CCH3)4]0/+ and [Ru2(micro-O2CCH3)4(H2O)2]0/+ systems made us confident in our calculation methodology. Therefore, it has been applied to the analysis of two different kinds of properties of these compounds: the trends in the UV/vis spectroscopy and electrochemistry along the [Ru2(micro-O2CCH3)4X2]- (X=Cl-, Br-, I-) series, and the crystalline polymorphism related to the polymeric strand conformation in extended Ru2(micro-O2CR)4Cl compounds. For the [Ru2(micro-O2CCH3)4X2]- series, we report new spectroscopic and electrochemical results and interpret the trends on the basis of time dependent DFT-polarized continuum model calculations, local charge and spin analysis, and X donor properties. As far as the polymeric conformation is concerned, it has been previously suggested that the Ru-Cl-Ru angle results from a compromise between packing, orbital overlap, and microsegregation. Our calculations on [Ru2(micro-O2CCH3)4Cl]2Cl- and [Ru2(micro-O2CCH3)4Cl]3Cl- oligomers provide insights on the influence of the first two factors on the strand conformation and allows a suggestion on what is the equatorial aliphatic chain's influence on this issue.