Synthesis and characterisation of oxovanadium(IV) complexes with tridentate ONO donor azo ligands

Reaction of VOSO4 with three tridentate dibasic ONO donor azo ligands (H2L1 -3, 1) separately in aqueous alcoholic medium produces complexes 2-4 of the type [VO(L)(H2O)(x)](y), where x = 1, y = 1 for H2L1 : complex 2; x = 0, y = 2 for H2L2 and H2L3 : complexes 3 and 4 respectively. Complex 2 shows no rmal magnetic moment for a d(1) system while 3 and 4 show subnormal behavio ur. This behaviour is explained in terms of metal-metal bonding, and the ma gnetic moment order, 2 > 3 > 4 is correlated with the basicity of the donor atoms. One bonded water molecule is present only in complex 2. Among the t hree complexes only 2 shows two ligand field transitions. All the three com plexes exhibit one LMCT transition and two intraligand transitions characte ristic for azo group. They display either irreversible or quasireversible o ne-electron oxidation peaks in DME The electrochemical behaviour has been r ationalised on the basis of basicity of the coordinating atoms.