UV-Vis, HPLC, and ¹H-NMR studies of the substitution reactions of some Pt(IV) complexes with 5'-GMP and L-histidine

Abstract

Substitution reactions of [PtCl4(en)] and [PtCl 4(dach)] with guanosine-5'-monophosphate (5'-GMP) and L-histidine were studied by different experimental methods. By UV-Vis spectrophotometry, these reactions were investigated under pseudo-first-order conditions at 310 K in 25 mmol Hepes buffer (pH = 7.2) and 10 mmol NaCl to prevent the hydrolysis of the complexes. [PtCl4(en)] reacts slightly faster than the [PtCl4(dach)]. Also, L-histidine is a better nucleophile than 5'-GMP. Final 1H-HMR spectra of the substitution of Pt(IV) were in a good agreement with the spectra of Pt(II) complexes with the same nucleophiles, confirming the assumption of the reduction of Pt(IV) complexes during substitution. The same reactions were studied by high-performance liquid chromatography comparing the chromatograms during the reaction. The changes in the intensity of signals and their retention time show that at the end of substitution, there is only one dominant product in the system. We conclude that substitution of these Pt(IV) complexes is followed by rapid reductive elimination and final product is substituted Pt(II) complex. © 2010 Taylor & Francis.