Preparation and characterisation of new oxovanadium(IV) Schiff base complexes derived from amino acids and aromatic o-hydroxyaldehydes

A range of mostly new oxovanadium(IV) complexes is described. They contain coordinated Schiff bases, made from natural amino acids (glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, threonine, aspartic acid, and histidine) and salicylaldehyde or such derivatives as 3-, 4-, or 5-methoxy-salicylaldehyde. The coordination sphere is completed by simple ligands like water, 2,2'-bipyridyl or pyridine. The compounds are character ised and the nature of their coordination spheres shown by analysis, TLC, a nd by appropriate spectroscopy (EPR, IR, electronic and circular dichroism of solution and solids). In a few cases, magnetic properties are described to establish oxidation state. In several cases, the solubility of the compo unds from racemic amino acids differs markedly from those containing the si ngle enantiomer. The crystal and molecular structure of the related (and no vel) compound with N-pyridoxylidene-D,L-isoleucinate, [VO(pyr-D,L-Ile)(bipy )]. H2O is described. It contains two diastereomers. Denoting the chiral va nadium centres as A or C, these are [A(pyr-L-Ile)(bipy)] and [C(pyr-D-Ile)( bipy)]. (C) 1999 Elsevier Science S.A. All rights reserved.