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 center dot center dot center dot 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 center dot mol(-1) and -6.9--35.8 kJ center dot 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 sigma*(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.