Issue 2, 1986

Effects of mixed-ligand complex formation on deprotonation of amide groups in acid amides and peptides

Abstract

The stability constants of the parent complexes of the A ligands glycinamide, glycylglycinamide, and N-acetylhistidine with copper(II), and of the mixed complexes formed with the B ligands glycine, 2,3-diaminopropionic acid, tiron, histamine, L-histidine, and 2,2′-bipyridyl, have been determined from pH-metric measurements. It has been found that glycinamide forms mixed-ligand complexes of composition [CuAB] and [CuABH–1](charges omitted), and most favourably with histamine, L-histidine, or 2,2′-bipyridyl. In the glycylglycinamide complexes of type [CuABH–1] the B ligand is co-ordinated to a considerable extent via two equatorial sites, while the bonding in the complex [CuABH–2], similarly to the other dipeptides, is mainly axial–equatorial. In the parent complexes of copper(II) with N-acetylhistidine and with N-acetylhistamine, deprotonation and co-ordination of the amide group could not be detected. It has been found, however, that the presence of B ligands containing an aromatic N donor permits deprotonation of the amide groups in both N-acetylhistidine and N-acetylhistamine.

Article information

Article type
Paper

J. Chem. Soc., Dalton Trans., 1986, 235-239

Effects of mixed-ligand complex formation on deprotonation of amide groups in acid amides and peptides

I. Sóvágó, B. Harman, A. Gergely and B. Radomska, J. Chem. Soc., Dalton Trans., 1986, 235 DOI: 10.1039/DT9860000235

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