Chromium(III) complexes of L(+)-cysteine, DL-penicillamine and L(-)-cystine. Synthesis and spectromagnetic characterization

Chromium(III) chloro-complexes with L(+)-cysteine, dl-penicillamine and l(-)-cystine were isolated and characterized by their vibrational, electronic and spectromagnetic properties. The coordination of sulphur containing amino acids involves amino and/or carboxylato groups; only in the case of penicillamine the mercapto group shows bonding with metal. The difference in the relative strength of binding sites, in the compounds here reported, is related to the σ -donor and π -acceptor properties of sulphur containing amino acids; specifically coordination of mercapto group becomes possible if amino and carboxylato groups supply to chromium the electronic charge required for the back-donation to dπ sulphur orbitals.