Monooxovanadium(V) mixed ligand complexes of Schiff bases and catecholates : synthesis, spectral and electrochemical characterization

Abstract

Mixed ligand, monooxovanadium(V) complexes of Schiff bases with catechol, p-tertbutylcatechol or pyrogallol have been synthesized and characterized by various spectral techniques, such as FTIR, UV-vis, ⁵¹V NMR and electrochemistry. All of these complexes exhibited a six coordinated VO³⁺ center. The stability and the conversion of these complexes to pentacoordinated VO₂⁺ species with the loss of a bidentate catecholate ligand in DMSO were demonstrated using absorption, ⁵¹V NMR and electrochemical studies. ⁵¹V NMR studies further suggested the formation of two possible isomers in the case of p-tertbutylcatechol and pyrogallol complexes of VO³⁺. Electrochemistry of these complexes showed one reversible V(V)/V(IV) couple and another irreversible V(IV)/V(11I) response. The mixed ligand, VO³⁺ complexes are more resistant to reduction as compared to the corresponding tris catecholate complexes.