Exploring the nature of electron-pair bonds: an energy decomposition analysis perspective

Abstract

Abstract In this paper, the nature of electron-pair bonds is explored from an energy decomposition perspective. The recently developed valence bond energy decomposition analysis (VB-EDA) scheme is extended for the classification of electron-pair bonds, which divides the bond dissociation energy into frozen, reference state switch, quasi-resonance and polarization terms. VB-EDA investigations are devoted to a series of electron-pair bonds, including the covalent bonds (H–H, H3C–CH3, H3C–H, and H2N–NH2), the ionic bonds (Na–Cl, Li–F), the charge-shift (CS) bonds (HO–OH, F–F, Cl–Cl, Br–Br, H–F, F–Cl, H3Si–F and H3Si–Cl), and the inverted central carbon–carbon bond in [1.1.1] propallene. It is shown that the VB-EDA approach at the VBSCF level is capable of predicting the characters of the electron-pair bonds. The perspective from VB-EDA illustrates that a relatively high value of quasi-resonance term indicates a CS bond while a large portion of polarization term suggests a classical covalent bond.