Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (3): 435-440.doi: 10.3866/PKU.WHXB201501211


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


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