Bond energies (Pt-NH3, Pt-Cl) and proton affinity of cisplatin: A density functional theory approach

The energies of the Pt-NH3 and Pt-Cl bonds of cisplatin are calculated by means of a density functional theory method with the B3LYP functional and various basis sets. The calculated bond energies of 37.38 kcal·mol−1 and 64.35 kcal·mol−1 for Pt-NH3 and Pt-Cl, respectively, agree well with the experimental values (37.28 kcal·mol−1 and 69.31 kcal·mol−1 respectively) derived from enthalpy changes. The proton and lithium ion affinities of cisplatin are also obtained with the B3LYP functional. Structural characterizations for the protonated and lithiated cisplatin complexes are given. Protonation and lithiation alter the geometric parameters, and the gas-phase proton affinity (198.71 kcal·mol−1) is much higher than the lithium ion affinity (70.32 kcal·mol−1).