Mixed-ligand oxovanadium(V) complexes incorporating bidentate salicylaldehyde and tridentate aldimine ligands

Mixed-ligand oxovanadium(V) complexes, [(VO)-O-v(L)-(sal)], containing salicylaldimine ligands of alpha-amino acids H(2)L [(1); R = Me, i-Pr and CH(2)Ph] and salicylaldehyde (Hsal) have been synthesized. The coordination sphere of the complexes is of the VO(ONO)(OO) type, where O atoms are phenolic, carboxylic and aldehydic, and N is of the azomethine type. The complexes are diamagnetic and exhibit only one LMCT band at ca. 490 nm. They display quasi-reversible one-electron reduction peaks in a CH2Cl2-MeCN (2:1 v/v) mixture in the 0.07-0.13 V versus s.c.e. range. A trend in the redox potential data has been rationalized on the basis of conventional normal substituent effects.