SYNTHESIS AND STRUCTURE OF CARBOXYL-BONDED OXOVANADIUM(V) COMPLEXES INCORPORATING ALPHA-AMINO-ACID SALICYLALDIMINATES AND QUINOLIN-8-OLATE

The complexes [VO(L(1))(hquin)] and [VO(L(2))(hquin)] incorporating N- salicylidene-glycinate and -L-phenylalaninate respectively have been s ynthesised in excellent yields from [(VO)-O-IV(L)(H2O)] and quinolin-8 -ol (Hhquin) in air which acts as the oxidant. The crystal structure o f [VO(L(2))(hquin)] revealed tridentate ONO and bidentate ON binding b y [L(2)](2-) and hquin(-) respectively. The V-O (carboxylate) bond len gth is longer than V-O (phenolate) by approximate to 0.1 Angstrom. The CD spectrum of [VO(L(2))(hquin)] in the visible region revealed the c omposite nature of the phenolato-->vanadium charge-transfer band. The absolute configuration of [VO(L(2))(hquin)] is CS both in the crystall ine state and in solution. In CDCl3 solution the H-1 NMR spectrum of t he complex shows that the amino acid side chain has the same conformat ion as that in the crystal lattice. The complexes display the quasi-re versible one-electron couple [VO(L)(hquin)]-[VO(L)(hquin)](-) near 0.0 V vs. saturated calomel electrode. Electrogenerated solutions of [VO( L)(hquin)](-) are EPR-active corresponding to a d(xy)(1) configuration .