Six-membered electron transfer series [V(dithiolene)_3] ~z (z = 1+, 0, 1-, 2-, 3-, 4-). An X-ray absorption spectroscopic and density functional theoretical study

摘要

The electronic structures of vanadium centers coordinated by three dithiolene ligands have been elucidated by using a host of physical methods: X-ray crystallography, cyclic voltammetry, electronic absorption, electron paramagnetic resonance (EPR), and X-ray absorption spectroscopies, augmented by density functional theoretical (DFT) calculations. The consensus electronic structure derived from this approach is a V(IV) central ion for the neutral, monoanionic, and dianionic members of this electron transfer series, where the tris(dithiolene) ligand units are (L_3)~(4-), (L _3)~(5-·), and (L_3)~(6-), respectively. The trigonal prismatic monoanions, [V~(IV)(L _3~(5-·))]~(1-) (S = 0), are defined as singlet diradicals where the crystallographically observed dithiolene fold results from strong antiferromagnetic coupling between the metal-and ligand-based magnetic orbitals. These results are contrasted with the corresponding tris(dioxolene)vanadium electron transfer series toward establishing the factors that govern the molecular trigonal prismatic or octahedral geometries in systems with three redox noninnocent ligands.