Spectroscopic and potentiometric studies on the interaction of trans-[(MeH2N)2Pt(mcyt)2PdCl]NO3(mcyt = 1-methylcytosinate) with derivatives of amino acids

Abstract

The interaction of the mixed-metal complex trans-[(MeH₂N)₂Pt(mcyt)₂PdCl]NO₃(mcyt = 1-methyl-cytosinate) with various derivatives of amino acids mimicking the side-chain metal binding sites of proteins were studied by ¹H NMR, spectrophotometric and potentiometric methods. The derivatives included N-acetylamino acids (N-acetyl-methionine, -cysteine, -lysine, -histidine and -histamine), amino acids (glycine and methionine) and dipeptides (Gly-Met and Gly-Lys). The co-ordination of independent thioether, amino or imidazole nitrogen side-chain donor groups resulted in the formation of stable mono- or di-nuclear adducts. The formation of dinuclear complexes was characteristic of dipeptides and N-acetyl-histidine and -histamine. The existence of linkage isomers was demonstrated in the latter case, the Pd–N(3)(imidazole) isomers being more favoured. The possibility of stable chelate formation with palladium(II)(e.g. S,O for N-acetylcysteine and S, N for methionine) significantly enhanced the decomposition of the mixed-metal complex, leading to trans-[Pt(NH₂Me)₂(Hmcyt)₂]²⁺.