SPECTROSCOPIC ANALYSIS OF BINARY AND TERNARY COPPER(II) COMPLEXES FORMED BY HISTIDINE AND GLUTAMIC ACID

Abstract
Ternary copper(II) complexes of the type [Cu(His)A] (HisH=L-histidine, A=glycinato, L-valinato, L-alaninato, L-threoninato, L-serinato, or L-asparaginato) and [Cu(Glu)B]n- (GluH2=L-glutamic acid, B=glycinato, L-alaninato, L-valinato (n=1) or an amino-acid with positively charged protonated side chain such as L-asparagine, L-lysine, or L-ornithine (n=0)) have been investigated in aqueous solution by means of ESR and absorption spectra. It is suggested that in the ternary species the histidinate ion adopts a histamine-like bonding mode giving rise to CuN3O chromophores in the metal plane. Coordination in the bis-(glycine)-like mode is detected in the Glu-containing species. The spectral results have been used to postulate plausible structures for the bis-(histidinato)copper(II) complexes.

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