Theoretical study of the potential energy surface for the interaction of cisplatin and their aquated species with water

In this work, a systematic study of the interaction of neutral cisplatin ([Pt(NH3)(2)Cl-2]) and their charged aquated species ([Pt(NH3)(2)Cl(H2O)](+) and [Pt(NH3)(2)(H2O)(2)](2+)) with water was carried out. The potential energy surface (PES) was analyzed by considering 35 spatial orientations for the interacting species. The calculations were performed at various levels of theory including Moller-Plesset fourth order perturbation theory and density functional theory (DFT-B3LYP) using extended basis sets. Lennard-Jones (12-6) plus Coulomb classical potential was also used to assess the repulsion-dispersion and electrostatic contributions. The effect of atomic charges on the interaction energies is discussed using Mulliken, charges from electrostatic potential grid method and natural bond orbital schemes. The outcomes show that the electrostatic term plays a primary role on the calculation of interaction energies, with the absolute values of atomic charges from different approaches significantly affecting the overall interaction. Unusual results were revealed by basis set superposition error calculations for the structures located on the platinum-water PES. (c) 2008 American Institute of Physics.