Synthesis and characterization of some chromium(III) complexes with glutathione

Abstract

The glutathione (H₅L) complexes K₂[Cr(H₃L)(H₂L)]·3H₂O, K₂[Cr(H₂L)(A)]·nH₂O (A = the dianion of the amino acids L-cysteine, L-glutamic acid, or L-aspartic acid), and K₂[Cr(H₂L)(gly)(OH)]·2H₂O [gly = glycinate(1–)] have been synthesized. All the complexes exhibit an intense u.v. chargetransfer band which is characteristic of a Cr–S bond. The sulphydryl to chromium linkage undergoes an acid-catalysed hydrolysis. The complexes have been characterized by elemental and thermogravimetric analyses, electronic and i.r. spectroscopy, and circular dichroism. Comparison of these properties with those of known chromium(III) complexes leads to the conclusion that glutathione is bound to chromium(III) by the terminal glycine group (N,O) and the deprotonated sulphur of cysteine. The glutamic acid residue of glutathione does not apparently interact with the chromium centre in these complexes.