Effects of imidazole and zinc on the interaction of some amino acid compounds of copper(II) with hydrogen peroxide

Abstract

A novel effect of the inhibition of the decomposition of amino acids to carbonates on addition of imidazole (HIm) to a reacting system containing equimolar amounts of copper and zinc metal powders, an amino acid [glycine (Hgly), aspartic acid (H2Asp) or glycylglycine (H2gg)] (1:1:2) and excess hydrogen peroxide (H2O2) resulting in formation of a mixed metal mixed ligand peroxo complex compound was observed, because in the absence of imidazole the corresponding reaction system yields only a mixed metal peroxo carbonate. For the resulting complex compounds, the homogeneity, i.e. [Cu(Zn)(O22−)(Gly)2(HIm)(H2O)], [Cu(Zn)(O22−)(Asp)(HIm)(H2O)2] or [Cu(Zn)2(O22−)2(gg)(HIm)(H2O)4], molecular formula, presence of peroxo group and coordination environment were established by combined physicochemical evidence from elemental and thermogravimetric analysis in air and argon atmospheres, electron spin resonance and electronic and IR spectral data. It is noteworthy to mention that the corresponding carboxylic acids of the above-mentioned amino acids, i.e. acetic and succinic acids, either do not decompose to carbonates in the absence of imidazole or form novel homogeneous peroxo mixed metal mixed ligand complex compounds as described above in the presence of imidazole. This suggests an important and significant mutual influence (in vitro) of biologically active chromophores like peroxo ions, imidazole and amino groups in the above-mentioned chemical reactions containing bioactive metals such as copper and zinc.