NH_3AlH_3与若干小分子的双氢键的理论研究

Theoretical Study on Dihydrogen Bonds of NH_3AlH_3 with Several Small Molecules

运用量子化学从头算方法研究了NH3AlH3与HF,HCl,HBr,H2O和CH3OH形成的双氢键Al—H…H—X(X=F,Cl,Br,O).计算结果表明,在所有体系中,双氢键的形成使得AlH和HX键增长,伸缩振动频率红移.分子间超共轭σ(AlH)σ*(XH)导致了XH键的红移.AlH键红移由两个因素造成:AlH键发生负的重极化与负的重杂化;分子间超共轭导致σ(AlH)成键轨道电子密度减小.

The dihydrogen bonds Al--H...H--X（X=F, Cl, Br, O） of NH3AlH3 with HF, HCl, HBr, H2O and CH3OH are theoretically studied with quantum chemistry ab initio calculation. The results show that the formation of dihydrogen H-bonds leads to red shifts of AlH and XH bonds in all the above systems. The red shifts of XH bonds are caused by the intermolecular hyperconjugation σ（AlH） →σ（XH） ; the red shifts of AlH bonds are caused by two factors： negative replorization and negative rehybridization; and decrease of occupancy on σ（AlH） are caused by the intermolecular hyperconjugation σ（BH） →σ＊ （XH）.