Electrochemistry and Bioactivity Relationship of Pt(IV) Complexes with Cyclohexyl-Functionalized Ethylenediamine-N,N '-Diacetate-Type Ligands

Abstract

Pt(IV) complexes with ethylenediamine-N,N'-diacetate-type ligands exhibit strong antitumor activity towards various cancer cell lines. In order to explain their complete mechanisms of action, we examined bioreductive character of eight compounds in total using cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. Recorded voltammograms of all Pt(IV) complexes with methyl, ethyl, n-propyl and n-butyl esters of (S,S)-ethylenediamine-N,N'-di-2-(3-cyclohexyl)propanoic acid confirmed two successive one-electron transfer steps followed by the loss of the corresponding axial ligands. The redox potential values for Pt(IV) complexes were in the range of -0.92 V lt Ep lt -0.70 V vs. Ag/AgCl, indicating hard reduction. The obtained electrochemical data pointed to the fact that the length of alkyl substituents influences on the reduction as well as on their biological activity. In addition, the electrochemical data were correlated with the biological data but this correlation wasn't established. The reported electrochemical data well correlated with the biological results pointed to the future structural modifications among the investigated compounds and helped select the most suitable candidates for further research.