EXPLORING THE PNICOGEN BOND IN THE X-Ph-NH2:PFnH3-n COMPLEXES USING AB INITIO APPROACH

Quantum chemical calculations have been carried out to study of the structures, binding energies, and bonding properties of the pnicogen-bonded complexes of X-Ph-NH2:PFnH3-n with the substituents including X= H, F, CN, CHO, NH2, CH3, NO2 and OCH3. Ab initio calculations were performed using MP2 and M06-2X methods. The changes in the Pnicogen bond (PB) strength due to variation of the substituents were well monitored by changes in the interaction energy, structural parameter, electron density topology, natural charge and charge transfer. The results demonstrate that the strength of the pnicogen bond increases by electron-donating substituents. The reverse situations were found for electron-accepting substituents. Complexation of PF3 with the X-Ph-NH2 leads to P•••N bonds with a significant degree of covalency. The electron density topology properties based on atoms in molecules (AIM) theory showed that the PB interactions in the X-Ph-NH2:PF3 (X=NH2, OCH3, CH3 and H) are stronger than those of X-Ph-NH2:PF3 (X= F, CHO, CN and NO2) complexes, indicating that the electron-donating of X benefits for the stability of PB structure.