Halide Recognition by Tetraoxacalix[2]arene[2]triazine Receptors : Concurrent Noncovalent Halide-π and Lone-pair-π Interactions in Host-Halide-Water Ternary Complexes

摘要

Anion recognition has attracted much attention because of its importance in biological and environmental sciences. A large number of synthetic host molecules have been synthesized for the purpose of anion complexation. Noticeably, almost all synthetic anion receptors were designed to exploit hydrogen bonding, electrostatic interactions, hydrophobic effects, and coordination to metal ions. In recent years, however, there has been a growing interest in anion-π interactions, the interaction between an anion and an electron-deficient π-arene species. A number of theoretical studies, for example, have reported the noncovalent interactions of anions with aromatic compounds such as perfluoro-, nitro-, and cyano-substituted benzene, pyridine, pyrazine, and triazine derivatives. Experimental evidence to support the purely noncovalent anion-π interaction with charge-neutral arenes, however, is very rare. A recent study indicated indeed that the noncovalent anion-π interaction contributed less significantly than hydrogen bonding to the formation of the complex chloride-π-C6F_nH_(6-n) (n = 0-5).