Benzimidazolium-based chemosensors: selective recognition of H2PO4−, HP2O73−, F− and ATP through fluorescence and gelation studies

Benzimidazolium-based receptors 1 and 2 have been designed and synthesized. The receptors with identical binding sites exhibit different sensing properties towards different anions under identical conditions. In a lower equivalent amount of guests, receptors 1 and 2 show fluorescence selectivity towards phosphate-based anions. In the presence of higher equivalent amounts of guests, while structure 1 reveals selectivity in sensing of phosphate derivatives such as hydrogen pyrophosphate and dihydrogenphosphate in CH3CN, under identical conditions receptor structure 2 senses F−. Furthermore, compounds 1 and 2 validate the visual sensing of hydrogen pyrophosphate and dihydrogenphosphate, respectively, through the formation of gels. Binding studies have been carried out using fluorescence, UV-vis, 1H NMR and 31P NMR spectroscopic techniques. Experimental results have been correlated with the theoretical findings.