物理化学学报 >> 2015, Vol. 31 >> Issue (3): 435-440.doi: 10.3866/PKU.WHXB201501211

理论与计算化学 上一篇    下一篇

H2XP…SHY复合物中磷键与硫键的理论研究

刘玉震, 黎安勇   

  1. 西南大学化学化工学院, 重庆 400715
  • 收稿日期:2014-12-01 修回日期:2015-01-21 发布日期:2015-03-06
  • 通讯作者: 黎安勇 E-mail:aylifnsy@swu.edu.cn

Theoretical Analysis of Pnicogen and Chalcogen Bonds in H2XP…SHY Complexes

LIU Yu-Zhen, LI An-Yong   

  1. School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, P. R. China
  • Received:2014-12-01 Revised:2015-01-21 Published:2015-03-06
  • Contact: LI An-Yong E-mail:aylifnsy@swu.edu.cn

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摘要：

用从头算量子化学方法MP2 与CCSD(T)研究了H2XP和SHY (X, Y=H, F, Cl, Br)分子的P与S之间形成的磷键X―P…S与硫键Y―S…P的本质与规律以及取代基X与Y对成键的影响. 计算结果表明, 硫键比磷键强, 连接在Lewis 酸上的取代基的电负性增大导致形成的磷键或硫键增强, 键能增大, 对单体的结构和性质的影响也增大; 而连接在Lewis 碱上的取代基效应则相反. 硫键键能为8.37-23.45 kJ·mol-1, 最强的硫键结构是Y 电负性最大而X 电负性最小的HFS…PH3, CCSD(T)计算的键能是16.04 kJ·mol-1; 磷键键能为7.54-14.65 kJ·mol-1, 最强的磷键结构是X 电负性最大而Y 电负性最小的H2FP…SH2, CCSD(T)计算的键能是12.52 kJ·mol-1. 对磷键与硫键能量贡献较大的是交换与静电作用. 分子间超共轭lp(S)-σ*(PX)与lp(P)-σ*(SY)对磷键与硫键的形成起着重要作用, 它导致单体的极化, 其中硫键的极化效应较大, 从而有一定的共价特征.

关键词: σ-hole, 磷键, 硫键, 取代基效应

Abstract:

The MP2 and CCSD(T) ab initio quantum chemistry methods were applied to study the pnicogen bonds X―P…S and chalcogen bonds Y―S…P formed between PH2X and SHY (X, Y=H, F, Cl, Br) and the effects of the substituents X and Y on the bonds. Calculated results show that the chalcogen bonds are stronger than the pnicogen bonds. Strongly electronegative substituents that are connected to the Lewis acid strengthened the bonds and significantly affected the structures and properties of the monomers. Conversely, the substituents connected to the Lewis bases produced opposite effects. The energies of chalcogen bonds were 8.37-23.45 kJ·mol-1; the strongest chalcogen bond was found in the structure HFS-PH3 using the CCSD (T) method with a bonding energy of 16.04 kJ·mol-1. The energies of pnicogen bonds were in the range 7.54-14.65 kJ·mol-1; the strongest pnicogen bond was found in H2FP-SH2 using CCSD(T) with a bonding energy 12.52 kJ·mol-1. The most important factors for bond strength for both types of bonds were the exchange and electrostatic energies. The hyperconjugations lp(S)-σ*(PX) and lp(P)-σ*(SY) play important roles in the formation of the pnicogen and chalcogen bonds, which both lead to polarization of the monomers. Polarization caused by the chalcogen bond is larger than that by the pnicogen bond, resulting in the chalcogen bond having less of a covalent character.

Key words: σ-hole, Pnicogen bond, Chalcogen bond, Substituent effect