Kinetics of the substitution reactions of some Pt(II) complexes with 5'-GMP and L -histidine

Abstract

The reactions of platinum(II) complexes, [PtCl2(dach)] (dach = (1R,2R)-1,2-diaminocyclohexane) and [PtCl2(en)] (en = ethylenediamine) with biologically relevant ligands such as 5'-GMP (guanosine-5'-monophosphate) and l-His (l-histidine) were studied by UV-vis spectrophotometry, 1H NMR spectroscopy, and high-performance liquid chromatography (HPLC). Spectrophotometrically, these reactions were investigated under pseudo-first-order conditions at 310 K in 25 mM Hepes buffer (pH 7.2) and 10 mM NaCl to prevent the hydrolysis of the complexes. The [PtCl 2(en)] complex reacts faster than [PtCl2(dach)] in the reaction with studied nucleophiles. This confirms the fact that the reactivity of studied Pt(II) complexes depends on the structure of the inert bidentate ligand. Also, the substitution reactions with l-His are always faster than the reactions with nucleotide 5'-GMP. The reactions of [PtCl2(dach)] and [PtCl2(en)] complexes with l-histidine are studied by 1H NMR spectroscopy. The obtained rate constants are in agreement with those obtained by UV-vis. The same reactions were studied by HPLC comparing the obtained chromatograms during the reaction. The changes in intensity of signals of the free and coordinated ligand show that after a few days there is only one dominant product in the system. © 2010 Wiley Periodicals, Inc.