Iodine-benzene charge-transfer complex: Potential energy surface and transition probabilities studied at several levels of theory

Abstract

We present the results of detailed studies of the potential energy surfaces of the iodine–benzene charge-transfer complex obtained from (fully counterpoise corrected) ab initio calculations at the second-order Møller–Plesset (MP2) level and from (semi-)classical calculations. The most stable conformations found were the above-bond and the above-carbon conformations. The axial conformation was found to be somewhat less stable. The remarkable difference in intermolecular distance for different orientations of the iodine is explained in terms of the polarization anisotropy. This feature makes the construction of an accurate classical force field rather difficult because of the marked dependence of the repulsion parameter—usually the radius—for iodine on both orientation and polarization of the iodine. Investigation of the oscillator strengths of different complex geometries shows that there are many conformations in which the charge-transfer excitation can take place. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 75: 709–723, 1999