Density functional studies of the pseudo-π.aσ charge-transfer complex between cyclopropane and chlorine monofluoride

Abstract

The pseudo-π.aσ charge-transfer complex formed by cyclopropane and chlorine monofluoride was studied with various approximate pure and hybrid density functional methods and the second-order Møller–Plesset (MP2) theory. The calculations demonstrate that one hybrid method, namely the so-called B3LYP, leads to reasonably good estimates of the experimentally measured rotational constants. In addition, the predicted B3LYP intermolecular distance is found also to be close to the experimental value. This lends confidence to the prediction of the intermolecular interaction energy, which is found to be 1.42 kcal mol^-1. It was also possible to calculate the number and energies of the vibrational states supported by the intermolecular stretching mode. Only five such states have been found. The performances of the various approximate density functionals and MP2 theory are compared and discussed. Finally, the analysis of the natural bond orbitals, which has been found to be very valuable in understanding the nature of the weak intermolecular interaction is discussed.