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Theoretical Study on Dihydrogen Bonds of NH3BH3 with Several Small Molecules
An-yong Li *,Li-fang Xu,Zhou Ling
Author NameAffiliationE-mail
An-yong Li * School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China aylifnsy@swu.edu.cn 
Li-fang Xu School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China  
Zhou Ling School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China  
Abstract:
The dihydrogen bonds B–H???H–X (X=F, Cl, Br, C, O, N) in the dimer (NH3BH3)2 and the complexes of NH3BH3 with HF, HCl, HBr, H2CO, H2O, and CH3OH were theoretically studied. The results show that formation of the dihydrogen bond leads to elongation and stretch frequency red shift of the BH and XH bonds, except that in the H2CO system, the CH bond blue shifts. For (NH3BH3)2 and the complexes of the halogenides, red shifts of the XH bonds are caused by the intermolecular hyperconjugation σ(BH)→σ*(XH). For the system of H2CO, a blue shift of the CH bond is caused by a decrease of the intramolecular hyperconjugation n(O) →σ¤(CH). In the other two systems, the red shift of OH bond is a secondary effect of the stronger traditional red-shifted H-bonds N–H???O. In all these systems, red shifts of the BH bonds are caused by two factors: negative repolarization and negative rehybridization of the BH bond, and decrease of occupancy on σ(BH) caused by the intermolecular hyperconjugation σ(BH)→σ¤(XH).
Key words:  B–H…H–X dihydrogen bond, Red and blue shift, Negative repolarization and negative rehybridization
FundProject:
Theoretical Study on Dihydrogen Bonds of NH3BH3 with Several Small Molecules
黎安勇 *,徐利芳,周菱
摘要:
运用量子化学从头算方法研究了NH3BH3与HF、HCl、HBr、H2CO、H2O和CH3OH形成的双氢键B–H???H–X (X=F、Cl、Br、C、O).计算结果表明,在所有体系中双氢键的形成使得BH和HX键长增长且伸缩振动频率红移(在H2CO体系中CH键长减小,频率蓝移).除了NH3BH3,在每个体系中还存在传统氢键N–H???X.对NH3BH3及其与卤化氢的复合体系,分子间超共轭σ(BH)–σ*(XH)导致了XH键的红移;对H2CO体系,分子内超共轭减小导致CH键蓝移;在其他体系中,传统的红移氢键N–H???X是主要的,双氢键较弱,XH键的红移只是传统氢键的次级效应.在所有这些体系中,BH键红移由两个因素造成:BH键发生负的重极化与负的重杂化,分子间超共轭导致σ(BH)成键轨道电子密度减小.
关键词:  双氢键,红移,蓝移,负的重极化与负的重杂化
DOI:10.1088/1674-0068/22/01/57-62
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