Fluorescent Imidazolium-Based Cyclophane for Detection of Guanosine-5′-triphosphate and I<sup>–</sup> in Aqueous Solution of Physiological pH

A new water-soluble and fluorescent imidazolium-anthracene cyclophane (<b>1</b>) effectively recognizes the biologically important GTP and I<sup>–</sup> over other anions in a 100% aqueous solution of physiological pH 7.4. Fluorescence and <sup>1</sup>H NMR spectra and ab initio calculations demonstrate that emission arises from the formation of an excimer state and quenching occurs upon GTP/I<sup>–</sup> binding through (C–H)<sup>+</sup>···A<sup>–</sup> hydrogen bond interactions.