Ricerc@Sapienza

Cisplatin (cis-diamminedichloroplatinum(II), cis-[PtCl2(NH3)2]), widely used drug in cancer treatment,
has been allowed to react with simple molecular targets (L) mimicking biological functional groups.
The selected molecules (L = acetamide, dimethylacetamide, urea and thiourea) react by ligand exchange
leading to cis-[PtCl(NH3)2(L)]+ complexes that have been assayed by ESI-MS, IRMPD spectroscopy and
computations in order to characterize their structure and platination site. Formal five-coordinate complexes are also delivered by ESI, [(PtCl(NH3)2(H2O)(L)]+, notably absent only when L is thiourea. IRMPD
spectroscopy combined with computational analysis has revealed non-covalent adducts of the reactant
aqua complex with an external ligand L corresponding to {cis-[PtCl(NH3)2(H2O)]+ · L}, reminiscent of
the Eigen-Wilkins encounter complex invoked in the ligand displacement path in solution. The complex,
successfully isolated in the gas phase, undergoes ligand exchange yielding cis-[PtCl(NH3)2(L)]+ + H2O
when activated by multiple IR photons, testifying at the same time both structure and reactivity.