An effective macrocyclic ionophore for F− ions that contains an array of positively charged imidazolium units has been prepared. The calix[4]imidazolium[2]pyridine cation formed a complex with F− ions in a 1:1 stoichiometry, as shown by binding studies using 1H NMR spectroscopic analysis, X‐ray crystallographic determination (see structure), and density functional calculations.

Quinoxaline derivatives (1−4) bearing two imidazolium moieties are found to strongly bind anions and show unique charge-transfer fluorescent responses to pyrophosphate and acetate, whereas they show excimer formation with other anions. Anion-binding studies are investigated with fluorescence and 1 H NMR analysis, single-crystal X-ray analysis, and theoretical calculations.Anions play a fundamental role in a wide range of chemical and biological processes, and numerous efforts have been devoted to the development of abiotic receptors for anionic species. 1 Sensors based on anion-induced changes in fluorescence 2 and intramolecular/intermolecular excimer formation 3 appear to be particularly attractive. On the other hand, given that carboxylic acids (or carboxylates) are a common functional group in biological and synthetic organic molecules, the development of simple to sophisticated receptors for carboxylates has attracted immense attention. 4 The imidazolium group can make a strong interaction with anions through the (C-H) + -X --type ionic hydrogen bond-ing involving the dominating charge-charge electrostatic interaction 5 which is in contrast to well-known neutral receptors involving typical hydrogen bonding for the anion

A new anthracene dimer connected by two imidazolium moieties has been systematically designed and synthesized as a fluorescent chemosensor for selective binding of H(2)PO(4)(-) over other anions, which have been examined using fluorescence and (1)H NMR and rationalized with ab initio study.