Quantum-Chemical theoretical study on blue-shifting hydrogen bonding complexes between CHCl2 , CDCl2 and S02 in the gas phase.

Abstract

The CH(D)Cl3OSO complexes geometries are studied by high level quantum chemical calculation, MP2/6-31 ++G(2d,2p). The interaction energies are corrected with ZPE and BSSE. Four complexes are obtained, in which three complexes have point group, C_s with binding energy about 2.18 - 2.20 kcal.mol^-1 and the last has point group C1 with energy about 2.16 - 2.17 kcal.mol^-1. In all complexes, there is a contraction of the C-H(D) bond, a shift to higher frequency called "blue-shift" of the C-H(D) stretching frequency compared to the CH(D)Cl3 monomes. However, there is an apparent increase of the IR intensity. The blue-shifts are 8.4. 5.9 cm^-1 in the CHCl3...OSO (C1) and CDCl3...OSO (C1 ), in good agreement with the experimental results 7 cm^-1, 5 cm^-1, respectively. The NBO analysis indicates that the Il-index is not reason for physical origin of blue-shifting hydrogen bond but the EDT is also reason for the contraction.