摘要:
运用量子化学从头算方法,研究了NH_2BH_2作为质子受体与HCF_3,HCCl_3,HF,HCl,HCOF和HCOCl作为质子给体形成的双氢键B-H…H-X(X=F,Cl,C).计算结果表明,在所有复合物中, BH键键长增长,伸缩振动频率红移;在HF与HCl的复合物中, XH键键长增长,伸缩振动频率红移;在其他复合物中, XH键键长缩短,伸缩振动频率蓝移.在每个体系中,还存在传统氢键N-H…Y (Y = F,Cl,O). AIM和NBO分析表明,在这些复合物中双氢键是以静电作用为主,振动频率红移蓝移的变化是因为分子间与分子内电子密度转移引起的,可以用Al-abugin的超共轭和重杂化理论进行解释,同时必须考虑分子内超共轭作用.
Abstract:
Ab initio quantum chemistry methods were employed to investigate the formation of dihydrogen bonds B-H...H-X(X=C, F, Cl) with NH_2BH_2 as the proton acceptor and some small molecules (HF, HCl, CHF3, HCCl_3, HCOCl and HCOF) as the proton donors. The calculation results indicated that the formation of dihydrogen bonds leads to red shift of the BH bond in all the systems, red shifts of the H-F and H-Cl bonds in the complexes of HF and HCl, and blue shift of the H-C bond in the complexes of CHF3, HCCl_3, HCOF and HCOCl. Traditional hydrogen bonds N-H...Y(Y=Cl, F, O) were found to exist in all the systems. The results of AIM and NBO analysis showed that electrostatic interaction was redominant in dihydrogen bonds and traditional hydrogen bonds in all the systems. The red and blue hifts of vibration frequency were caused by inter-and intra-molecular electron density transfer, and can be xplained with the theory of hyperconjugation and rehybridization proposed by Alabugin, where the intra-molecular hyperconjugation must be taken into account.
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