2,9-Dimethyl-1,10-phenanthroline copper(I) complexes with some sulphur-containing amino acids

Abstract

Complexes of [Cu(dmphen)_n]⁺(dmphen = 2,9-dimethyl-1,10-phenanthroline; n= 1 or 2) with several of the biologically relevant sulphur amino acids L (L = cysteine, penicillamine, methionine, N-acetylcysteine, and N-acetylpenicillamine) have been synthesized and characterised. I.r, and ¹H n.m.r. spectral results indicate that the amino group is protonated in the complexes containing sulphydryl amino acids; the carboxylic group remains unionised in complexes isolated from strongly acidic media while that in complexes isolated from nearly neutral solution ionises and co-ordinates to the Cu^I centre through one of the oxygen atoms. The Cu^I–S(sulphydryl) interaction in all complexes is exclusively one of sulphur→copper(I)σ donation, as supported by the relative magnitudes of the Cu–S stretching frequencies.