Heteronuclear complexes of phosphocreatine with copper(II) and magnesium(II) ions

Abstract

It has been found that in the binary systems Mg(II)/phosphocreatine and Cu(II)/phosphocreatine at low pH, metal ions mainly coordinate via the phosphate group. At higher pH for copper(II) system, the efficiency of -PO32- group is low and coordination takes place via amine and carboxyl groups (Mg2+ is still coordinated to phosphate group). Differences in the coordination mode for copper and magnesium ions in binary systems at high pH suggested that it would be interesting to determine the mode of coordination in heteronuclear complexes and the coordination competitiveness of metal ions towards phosphate group at low and at physiological pH. The formation of heteronuclear complexes of phosphocreatine with Mg2+ and Cu2+ ions was investigated. The overall stability constants of these species were determined by the potentiometric studies and the coordination mode was concluded on the basis of several spectral investigations (EPR, Visible Spectroscopy, 2D 1H-15N NMR, 31P NMR and FT-IR).