Equilibrium investigation of complex formation reactions involving copper(II), nitrilo-tris(methyl phosphonic acid) and amino acids, peptides ok DNA constitutents

摘要

The complex formation reactions of [Cu(NTP)(OH_2)]~(4-) (NTP = nitrilo-tris(methyl phosphonic acid)) with some selected bio-relevant ligands containing different functional groups, are investigated. Stoichiometry and stability constants for the complexes formed are reported. The results show that the ternary complexes are formed in a stepwise mechanism whereby NTP binds to copper(II), followed by coordination of amino acid, peptide or DNA. Copper(II) is found to form Cu(NTP)H_n species with n = 0, 1, 2 or 3. The concentration distribution of the various complex species has been evaluated. The kinetics of base hydrolysis of glycine methyl ester in the presence of copper(II)-NTP complex is studied in aqueous solution at different temperatures. It is proposed that the catalysis of GlyOMe ester occurs by attack of OH~- ion on the uncoordinated carbonyl carbon atom of the ester group. Activation parameters for the base hydrolysis of the complex [Cu(NTP)NH_2CH_2CO_2Me]~(4-) are, triangle open H~(+-) = 9.5+-0.3 kJ mol~(-1) and triangle open S~(+-) = -179.3+-0.9JK~(-1)mol~(-1). These show that catalysis is due to a substantial lowering of triangle open H~(+-).