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Issue 15, 1992
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Transition-metal complexes of carcinine, a peptide-type derivative of histamine

Abstract

The acid–base properties and copper(II), nickel(II) and cobalt(II) complexes of carcinine {3-amino-N-[2-(imidazol-4-yl)ethyl]propanamide} and of N-tert-butoxycarbonylcarcinine have been studied at 25 °C by pH-metric, spectrophotometric and, in part, 1H NMR and EPR methods, and compared to those of histidine-containing dipeptides. Complexes of the type M(HL), ML and ML2(charges omitted) are found in the cobalt(II) and nickel(II) systems, with the additional presence of ML2H–1 for the latter system. Copper(II) forms CuLn(n⩽ 4) complexes with N-tert-butoxycarbonylcarcinine molecules acting as monodentate ligands. The copper(II)–carcinine system in the range pH 3–9 shows the expected series of 1 : 1 complexes, more or less deprotonated depending on the pH, of type Cu(HL), CuL and CuLH–1, and, for an excess of ligand, the unusual 1 : 4 complex CuL4H2 involving four N(3) inidazole nitrogens equatorially co-ordinated. At higher pH (> 9) the monomeric CuLH–2 and polynuclear Cu4L4H–8 complexes are formed depending on the total concentration. The tetrameric species probably involves co-ordination of deprotonated N(1)-pyrrole nitrogens, with consequent formation of imidazolate bridges. The co-ordination ability of the peptide nitrogen in histidyl- and histamine-peptides is shown to depend on the size of the chelate rings formed and the existence of a neighbouring carboxyl group in the ligand.

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Article type: Paper
DOI: 10.1039/DT9920002313
Citation: J. Chem. Soc., Dalton Trans., 1992, 2313-2319
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    Transition-metal complexes of carcinine, a peptide-type derivative of histamine

    T. Gajda, B. Henry and J. Delpuech, J. Chem. Soc., Dalton Trans., 1992, 2313
    DOI: 10.1039/DT9920002313

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