Weak interaction between CH3SO and HOCl: Hydrogen bond, chlorine bond and oxygen bond

B3lyp/6–311++g** and mp2/6–311++g** calculations were used to analyze the interaction between CH3SO and HOCl. Nine (complex A: S1A–S9A) and five (complex B: S4B–S7B and S10B) minima were localized on the potential energy surface of CH3SO HOCl complexes at b3lyp/6–311++g** and mp2/6–311++g** computational levels, respectively. The AIM and NBO theories were also applied to explain the nature of the complexes. Bonding energy of complexes A and B corrected with BSSE falls in the ranges of 0.4– 41.4 kJ·mol 1 and 6.9– 35.8 kJ·mol 1 at mp2/6–311++g** level, respectively. The results show that a novel oxygen bond complex (S6) exists in the system, besides hydrogen bond and chlorine bond. Especially, S6B F, S6B Br and S7B are blue shifted complexes compared with red shifted S6A, because the electron transfer occurs between LP1(S8) and σ*(O5-Cl7), resulting in the increase of O5-Cl7 and the decrease of vibrational frequency. The complex of S10B has characteristics of both red shift and blue shift.