Calix[4]pyrroles bearing quinolinium moiety for halide sensing in aqueous solution

Sensing of chloride in aqueous solution with high selectivity is a challenging task and has a great potential for cellular imaging and analytical applications in food chemistry. Supramolecular binding motif calix[4]pyrrole has been conjugated with a known fluorescent probe for chloride – a quinolinium dye - through conformationally flexible and rigid linkers. Effects of the supramolecular host on the properties of the fluorescent dye and vice versa have been investigated by NMR, X-ray crystallographic and spectroscopic methods. New fluorescent probes have demonstrated better binding and quenching properties towards chloride, bromide and iodide in a 1:1 water-methanol mixture as compared to free calix[4]pyrrole and the quinolinium dye.