title: Orbital effect-induced anomalous anion-π interactions between electron-rich aromatic hydrocarbons and fluoride.
abstract: Anion-π interactions generally exist between an anion and an electron-deficient π-ring because of the electron-accepting character of the ring. In this paper, we report orbital effect-induced anomalous binding between electron-rich π systems and F(-) through anion-π interactions calculated at the MP2/6-31+G(d,p) and ωB97X-D/6-31+G(d,p) levels of theory. We find that anion-π interactions between F(-) and electron-rich π rings increase markedly with increasing number of π electrons and size of the π rings. This is contrary to intuition because anion-π interactions would be expected to gradually decrease because of gradually increasing Coulombic repulsion between the negative charge of the anions and gradually increasing number of π electrons of the aromatic surfaces. Energy decomposition analysis showed that the key to this anomalous effect is the more effective delocalization of negative charge to the unoccupied π* orbitals of larger π rings, which is termed an "orbital effect".
authors.affiliation: Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China). shiguosheng@sinap.ac.cn.
authors.forename: Guosheng
authors.initials: G
authors.lastname: Shi
authors.forename: Jinrong
authors.initials: J
authors.lastname: Yang
authors.forename: Yihong
authors.initials: Y
authors.lastname: Ding
authors.forename: Haiping
authors.initials: H
authors.lastname: Fang
keywords: anion-pi interactions; anions; density functional calculations; noncovalent interactions; receptors