环硼氮烷与HCl,CHCl_3构成的分子间氢键的理论研究

Theoretical study of the hydrogen bonding between borazine and HCl,CHCl_3

用MP2方法和B3LYP方法,在6-31G(d,p)基组下对复合物环硼氮烷—HCl体系和环硼氮烷—CHCl3体系进行优化,研究了其分子间氢键的本质。计算结果表明,氯仿与环硼氮烷分子之间的相互作用使C—H键长缩短,振动频率增大(蓝移),而HCl与环硼氮烷分子之间的相互作用使H—Cl键长增长,振动频率减小(红移)。自然键轨道(NBO)分析表明,影响氢键红移和蓝移主要有3个因素:n(Y)→σ*(X—H)超共轭作用、X—H键轨道再杂化和质子供体电子密度重排。其中,超共轭作用属于键伸长效应,电子密度重排和轨道再杂化属于键收缩效应。环硼氮烷—HCl体系的构型1和2伸长效应处于优势地位导致形成红移氢键;环硼氮烷—CHCl3体系中,由于键收缩效应处于优势地位导致形成蓝移氢键。

The geometries of borasine-HCl and borazine-CHCl3 complexes were calculated at the MP2 and B3LYP/6 -31G（d,p） levels, and the essence of the two intermolecular H - bond were researched. The results indicated that the interaction between chloroform and borazine shortened the length of the C-H bond and increased the vibration frequencies （blue - shifted ）, and the interaction between HCl and borazine increased the length of the H-Cl bond and decreased the vibration frequencies （red - shifted）. The NBO analysis showed that blue - shifted of the C-H bond and red - shifted of the H-Cl bond were controlled by a balance of three main factors：X-H bond lengthened by n（Y）→σ＊ （X-H） hypereonjugative interaction, X-H bond shortened by rehybridizative interaction and redistribution of electron density in proton donor. The elongation effect led to red - shifting H - bond in borazine-HCl system;the contractive effect in borazine-CHCl3 system led to blue -shifting H -bond.