Calix[n]imidazolium as a new class of positivelycharged homo-calix compounds

摘要

Macrocycles based on neutral calixarenes and calixpyrroles have been extensively exploredfor ion binding, molecular assembly and related applications. Given that only these two typesof calix compounds and their analogs are available, the introduction of new forms of widelyusable calix macrocycles is an outstanding challenge. Here we report the quadruply/quintuply charged imidazole-based homo-calix compounds, calix[4/5]imidazolium. Thenoncovalent (C-H)+/p+-anion interactions of the imidazolium rings with anions inside andoutside the cone are the stabilizing factors for crystal packing, resulting in self-assembledarrays of cone-shaped calix-imidazolium molecules. Calix[4]imidazolium senses fluorideselectively even in aqueous solutions. Calix[5]imidazolium recognizes neutral fullerenesthrough p+–p interactions and makes them soluble in water, which could be useful infullerene chemistry. Not only derivatization and ring expansion of calix[n]imidazolium,but also their utilization in ionic liquids, carbene chemistry and nanographite/grapheneexfoliation could be exploited.