Hydrolysis of cis- and transplatin: structure and reactivity of the aqua complexes in a solvent free environment

Abstract

Singly aquated and diaquated species are key intermediates in the mechanism responsible for the antitumor activity of cisplatin. Aqua complexes [PtX(NH₃)₂(H₂O)]⁺ (X = Cl, OH), obtained in water by hydrolysis of cisplatin and of the inactive isomer transplatin, are transferred into the gas-phase by electrospray ionization. The so-formed ions, cis- and trans-[PtX(NH₃)₂(H₂O)]⁺, have been allowed to react with selected ligands, representing platination targets in the biological environment. The reaction kinetics monitored in the gas-phase show consistently higher reactivity for the chloro complexes, [PtCl(NH₃)₂(H₂O)]⁺, with respect to the hydroxo counterparts, [Pt(OH)(NH₃)₂(H₂O)]⁺. The latter species, both cis- and trans-isomers, have been assayed by IRMPD spectroscopy in the NH/OH stretching region and their vibrational and geometric features are compared with the ones pertaining to the already described chloro complexes, cis- and trans-[PtCl(NH₃)₂(H₂O)]⁺.