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Comprehensive ab initio quantum mechanical and molecular orbital (MO) analysis of cisplatin: Structure, bonding, charge density, and vibrational frequencies

We carried out an extensive series of ab initio quantum mechanical (QM) calculations using pure effective core potential (ECP) and hybrid Hartree–Fock (HF)/ECP basis sets, including various electron correlation treatments up to the MP4 level on cis‐diamminedichloroplatinum(II), cisplatin, an important anticancer drug. The optimized geometric parameters and vibrational frequencies of cisplatin were compared with the experimental values, and the effects of varying basis sets and correlation (MP level) treatments on the geometric parameters and vibrational frequencies were analyzed. We also present a detailed description of the bonding in cisplatin using qualitative MO analysis to characterize the key intramolecular interactions in cisplatin. The calculated molecular electrostatic potential (MEP), and the electrostatic potential (ESP) charges for cisplatin were used to identify regions of electrophilic and nucleophilic character. The charge density and the Laplacian of charge density of cisplatin were calculated to determine its bonding relationships. Using basis set performance, we identified two hybrid basis sets (HF/6‐311G* and MP2/6‐311G*) as basis sets of choice for studying cisplatin's molecular properties. Furthermore, we recommend a hybrid ECP/HF approach with electron correlation for the most accurate physicochemical and electronic description of cisplatin and related compounds. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 365–382, 1999