Preparation and Structure of Zinc Complexes of Cysteine Derivatives

Abstract

Sodium bis(L-cvsteinatol zincate(II) hexahydrate (1) and bis(O-ethyl-L-cysteinato)zinc(II) (2) have been prepared from respectively alkaline (pH >11) and neutral aqueous solutions and their structures determined by X-ray structural analysis. N, S-coordination of the Zn atoms with the formation of two five-membered chelate rings is observed for both complexes. The deprotonated carboxylate groups in 1 do not coordinate the Zn atom. Dibromo-bis(DL-penicil-lamine)zinc(II) (3) and dibromo-bis(D-penicillamine)zinc(II) have been isolated from acid solutions with a pH of 2. The penicillamine moieties which are present in the zwitterionic form HS — C(CH3)2—CH(NH3+)—COO” behave as monodentate ligands with the deprotonated carboxylate group as binding site. The role of solution pH in determining the binding properties of cysteine and penicillamine with zinc(II) is discussed. © 1984, Verlag der Zeitschrift fü Naturforschung. All rights reserved.