CH3SH与HOCl分子间氢键和卤键的结构与性质

在DFT-B3LYP及MP2/6-311＋＋G**水平上分别求得CH3SH…HOCl氢键复合物和CH3SH…ClOH卤键复合物势能面上的稳定构型. 频率分析表明, 与单体HOCl相比, 在两种复合物中, Cl(9)—O(7)和H(8)—O(7)键伸缩振动频率发生显著的红移. 经MP2/6-311＋＋G**水平计算的含基组重叠误差(BSSE)校正的气相中相互作用能分别为－19.23和－6.85 kJ•mol－1. 自然键轨道理论(NBO)分析表明, 在CH3SH…ClOH卤键复合物中, 引起Cl(9)—O(7)键变长的因素包括2种电荷转移: (i)孤对电子LPS(1)]1→σ*Cl(9)—O(7)]; (ii)孤对电子LPS(1)]2→σ*Cl(9)—O(7)], 其中孤对电子LPS(1)]2→σ*Cl(9)—O(7)]转移占主要作用, 总的结果是使σ*Cl(10)—O(11)]的自然布居数增加, 同时O(7)和Cl(9)原子s成分均增加的杂化重优具有与电荷转移作用相同的“拉长效应”; 在CH3SH…HOCl氢键复合物中也存在类似的电荷转移, 但是O(7)原子的再杂化效应不同于前者. 自然键共振理论(NRT)进行键序分析表明, 在氢键复合物和卤键复合物中, H(8)—O(7)和Cl(9)—O(7)键的键序都减小. 通过分子中原子理论(AIM)分析了复合物中氢键和卤键的电子密度拓扑性质.

Structures and Properties of Halogen Bond and Hydrogen Bond Formed between CH3SH and HOCl

The optimized stable CH3SH…HOCl hydrogen bond and CH3SH…ClOH halogen bond complexes were located on the potential energy surface by means of DFT-B3LYP/6-311＋＋G**. The obvious red shifts of the H(8)—O(7) and Cl(9)—O(7) stretching vibrational frequencies in the two complexes were observed via frequency analysis. The halogen bond interaction energy of CH3SH…ClOH was －6.85 kJ•mol－1, and the hydrogen bond interaction energy of CH3SH…HOCl was －19.23 kJ•mol－1, which were calculated with basis set superposition error (BSSE) correction via a counterpoise procedure (CP) method. Natural bond orbital (NBO) theory analysis showed that two kinds of charge transfers exist in the CH3SH…ClOH halogen bond system: (i) lone pair LPS(1)]1→σ*Cl(9)—O(7)]; (ii) lone pair LPS(1)]2→σ*Cl(9)—O(7)], and the natural population of the σ*Cl(9)—O(7)] increased. Analogous charge transfers exist in the CH3SH…HOCl hydrogen bond complex. The bond order analysis with natural resonance theory (NRT) showed that bond order of Cl(9)—O(7) in the CH3SH…ClOH halogen bond complex and that of H(8)—O(7) in the CH3SH…HOCl hydrogen bond complex both decreased. The topological properties of the hydrogen bond and halogen bond structures were also investigated by the atoms-in-molecules (AIM) theory.