Solvolysis of a series of cisplatin-like complexes- comparison between dna-biosensor and conductivity data

The kinetics of solvolysis in pure dimethyl sulfoxide (DMSO) and water/DMSO or water/dimethylformamide (DMF) mixtures of a series of variously N-methylated ethylenediamine (en*) derivatives, cis-[PtCl₂(en*)], were studied by using an electrochemical biosensor consisting of DNA immobilized on the surface of screen-printed electrodes, by conductivity measurements, and by multinuclear NMR spectroscopy and ESI-MS techniques. The pattern of the kinetics was found to have significant differences between solvents, especially between the strongly coordinating DMSO and the weakly coordinating DMF co-solvent, employed to increase the solubility of the complexes under study. In particular, cisplatin and cis-[PtCl₂(en*)] show rapid solvolysis in the former but significantly slower in the latter, which indicates that the affinity of the Pt core for the S-donor atoms of DMSO overcomes the effect of its steric hindrance. In order to probe these reactions in more detail, density functional theory (DFT) calculations of activation barriers to solvolysis by both pure DMSO and H₂O were performed.