A comprehensive analysis of P center dot center dot center dot pi pnicogen bonds: substitution effects and comparison with Br center dot center dot center dot pi halogen bonds

摘要

Ab initio calculations were carried out in a systematic investigation of P center dot center dot center dot pi pnicogen-bonded complexes XH2P center dot center dot center dot C2H2/C2H4 and FH2P center dot center dot center dot C2R2/C2R4 for X=H, CH3, OH, CN, Br, Cl, NO2, F, and R=F, CH3, as well as corresponding Br center dot center dot center dot pi halogen-bonded complexes XBr center dot center dot center dot C2H2. Both the electron withdrawing and electron-donating substituents in the electron acceptor have enhancing effects on the strength of P center dot center dot center dot pi interactions. The electron-donating group in the electron donor leads to strengthening while the electron-withdrawing group leads to weakening of P center dot center dot center dot pi interactions. The studied P center dot center dot center dot pi and Br center dot center dot center dot pi interactions are similar and are typically "closed-shell" non-covalent character in nature. Moreover, analyses of natural bond orbital and density difference of molecular formation indicated that charge transfer and polarization also play important roles in P center dot center dot center dot pi interactions. The substituents have direct effects on the molecular electrostatic potential, and the charge transfer amount and extent of polarization of the P center dot center dot center dot pi interaction are also specific to each substituent.