Electrochemical and spectral behaviour of binary and mixed-ligand complexes of oxovanadium(IV) with dipicolinic acid and diimines in dimethylsulfoxide

The cyclic voltammetric (CV) studies of five binary oxovanadium (IV) complexes [VO(diimine)2]2 + where diimine = 4,4′-Me2bipy A; 5,5′-Me2bipy B; dmp C; bathophen D; and bathocuproin E and seven mixed-ligand oxovanadium (IV) complexes of dipicolinic acid (DPA) with diimines, [VO(DPA)(diimine)] where diimine = bipy 1; 4,4′-Me2bipy 2; 5,5′-Me2bipy 3; phen,4; dmp 5; bathophen 6 and bathocuproin 7 were carried out in dimethyl sulfoxide (DMSO). The reduction of binary [VO(diimine)2]2 + complex (VO2 +/V3 +) involving bathophen was the easiest while that involving dmp was the most difficult. The electronic spectra of all these binary [VO(diimine)2]2 + complexes in DMSO solution showed a weak broad band in the region 833–736 nm which was assigned to d–d transitions. The mixed-ligand complex involving 5,5′-Me2bipy was the easiest oxidation and bathophen was the most difficult to oxidize amongst all these complexes in the given medium. The reduction was the easiest in mixed-ligand complex involving bathophen and the most difficult in the case of dmp. The UV–visible spectra of all mixed ligand complexes were also studied in respective medium.