Abstract The Group 14-18 Elements of the Periodic Table can work as electrophilic sites and can form attractive interaction with electron-rich partners. The electrophilic sites have low density generally as electron density acceptor, and have positive molecular surface electrostatic potentials in most cases. The sites can be divided into two types. The positive surface electrostatic potential region of a molecular entity along extension of the covalent σ-bonding axis is named σ-hole, while the region with a positive surface electrostatic potential in the direction perpendicular to the σ-framework of the molecular entity can be called the π-hole. The attractive interaction between σ-hole or π-hole and electron-rich partner is named σ-hole bond or π-hole bond, respectively. The σ-hole bond is apt to 180 degree, and π-hole bond to 90 degree. According to the group names of the Element Periodic Table, σ-hole bond can be divided into some categories, including aerogen bond, halogen bond, chalcogen bond, pnictogen bond and tetrel bond, the current halogen bonding is a subset of σ-hole bonding. The classification of π-hole bond appears to be somewhat complicated, simply including single and multi-atoms π-hole bond.
CUI Yu-Jin, JIN Wei-Jun. Intermolecular Noncovalent Interactions: σ-Hole Bond and π-Hole Bond[J]. Chinese Journal of Chemical Education, 2018, 39(14): 1-11.
