First example of a 1:1 vanadium(IV)–citrate complex featuring the 2,2′-bipyridine co-ligand: Synthesis, X-ray crystal structure and DFT calculations

An unprecedented 1:1:1 complex [VO(bipy)(cit[H]H)]·1.5H2O was obtained from the reaction of vanadium(III) chloride, 2,2′-bipyridine (bipy), and citric acid (cit[H]H3) in methyl alcohol/water. The citrate anion (cit[H]H)2− chelates the metal centre as a tridentate ligand via the unusually protonated α-alcoholic group, and two oxygen atoms from the α- and one β-carboxylate groups, the other β-carboxylic acid group remaining uncoordinated. A pseudo-octahedral coordination sphere is completed by a bidentate bipy unit. The electronic nature of this complex is investigated by means of DFT calculations.