Spectroscopic studies on some sulphur-containing amino acid complexes of cobalt, nickel and copper

Abstract

The synthesis of three potentially sexadentate optically active sulphur-containing amino acids, 2,9- diamino-4,7-dithiadecanedioic acid [(R,R)-ebc], 2,ll-diamino-5,8-dithiadodecanedioic acid [(S,S)- ebhc] and 2,7-di(3'-thiabuty1)-3,6-diazaoctanedioic acid [(S,S)-ebm] are described. Some metal complexes of the acids with cobalt, nickel and copper are characterized by spectroscopic measurements. The complex   (-)₅₈₉[Co{(S,S)-ebm}] ClO₄ is formed stereospecifically and an X-ray structural analysis shows it to have the Δ-trans(O) configuration. The c.d. spectrum shows the presence of three bands due to the splitting of the T_1g energy level by the effective C₂ symmetry of the ligand field. Some polymeric cobalt(11) and nickel(11) complexes are also described. Spectral measurements indicate an octahedral coordination of the ligands involved. Several copper(11) complexes are also described.