NH_3BH_3的双接触蓝移双氢键的理论研究

Theoretical Studies on Bifurcated Blue-shifted Dihydrogen Bonds of NH_3BH_3

运用量子化学从头算方法研究了NH3BH3与含大的分子内超共轭的质子给体CHF3,H2CO,HCOOH,HCOCl和HNO形成的双接触弯曲双氢键B—H2…H—X(X=C,N)的分子结构、电子密度拓扑性质与频率位移特征.计算结果表明,在所有体系中,由于双氢键的形成,B—H键拉长且伸缩振动频率红移,而X—H键长减小且伸缩频率蓝移.弯曲的双接触构型导致分子间超共轭减小、X—H键的大的正重极化与正重杂化以及分子内超共轭减小三个因素导致了X—H键蓝移;B—H键红移的主要原因是B—H键的负的重极化与负的重杂化.

The bifurcated dihydrogen bonds B--H2 … H--X （X = C, N） of NH3 BH3 with CHF3, H2 CO, HCOOH, HCOC1 and HNO were theoretically studied. The results show that the dihydrogen H-bond leads to a red shift of the B--H bond and a blue shift of the X--H bond. The blue shift of the X--H bond is caused by the decrease of the intramoleeular hypereonjugation, positive repolarization and positive rebybridization of the X--H bond, and the bent configuration of the bifurcated dihydrogen bond ; The red shift of the B--H bond is caused mainly by negative replorization and negative rehybridization of the B--H bond.