New water-soluble fluorescent sensors based on calix[4]arene biscrown-6 for selective detection of cesium

Two new fluorescent chemosensors based on calix[4]arene bis(crown-6) bearing coumarin units have been synthesized for the detection of cesium ions in water. The photophysical and complexing properties of these sensors with cesium were investigated using absorption and fluorescence spectroscopies as well as DFT calculations. The coordination of Cs+ by the these ligands induces a better charge transfer between the donor and acceptor groups of the coumarin, resulting in a bathochromic shift in absorption spectra and an enhancement of emission spectra. Both the ligands display an excellent selectivity for Cs+ over other potentially interfering cations such as Na+, Li+, K+, Mg2+, Ca2+ and Sr2+ ions.