Theoretical exploration of pnicogen bond noncovalent interactions in HCHO⋯PH2X (X=CH3, H, C6H5, F, Cl, Br, and NO2) complexes

Abstract

Pnicogen bond (ZB) is a new kind of intermolecular weak interaction, which would be an important strategy for the construction of supramolecular materials. In this paper, ab initio MP2/aug-cc-pvDZ calculations have been carried out to characterize the X-P⋯O ZB interactions between HCHO and PH2X (X=CH3, H, C6H5, F, Cl, Br, and NO2). The calculated interaction energies with basis set super-position error (BSSE) corrections in seven ZB complexes are between −7.51 and −20.36 kJ⋅mol−1. The relative stabilities of the seven complexes increase in the order: HCHO⋯PH2CH3<HCHO⋯PH3<HCHO⋯PH2C6H5< HCHO⋯PH2Br < HCHO⋯PH2Cl < HCHO⋯PH2F < HCHO⋯PH2NO2. The natural bond orbital (NBO) and natural resonance theory (NRT) analysis were employed to investigate the electron behavior and nature of the ZBs. The natural bond orbital interactions in the ZBs are mainly LP 1,2(O) →σ*(P-X). The P-X (X = Br, Cl, F and NO2) are more suitable for acting as ZB donors than the P-X (X =H, CH3 and C6H5) groups. The electron density topology properties based on atoms-inmolecules (AIM) theory showed that the ZB interactions in the HCHO⋯PH 2X (X=Br, Cl, F and NO2) are stronger than those of HCHO⋯PH2X(X=CH3, H and C6H5) complexes, indicating that the electron withdrawing of X benefits for the stability of ZB structure. The pnicogen bond (ZB) intermolecular noncovalent interactions between HCHO and PH2X (X= CH3, H, C6H5, F, Cl, Br, and NO2) have been theoretically investigated at the MP2/aug-cc-pvdz computational level of theory, and the electron structure and properties of the O···P-X ZB are characterized by natural bond orbital, natural resonance and atoms-in-molecule theories.