Thiazole-based chemosensor III: Synthesis and fluorescence sensing of CH₃CO₂^- based on inhibition of ESIPT

Novel fluorogenic sensors based on urea derivative of 2-(2′- aminophenyl)-4-phenylthiazole (4 and 5) were prepared and used for recognition of anions with similar basicity and surface charge density. Chemosensor 4 was found to be highly selective to acetate ion over other anions. The selectivity was related to the structure matching between the host and the guest. The evaluation of the chemosensors' interaction with anions was performed by UV-vis and fluorescence titration. This acetate binding affinity was further tuned by varying the acidity of the N-H proton of the urea moiety in chemosensor 5. Novel fluorogenic sensors based on urea derivative of 2-(2′-aminophenyl)-4- phenylthiazole were prepared and used for recognition of anions with similar basicity and surface charge density. Chemosensor 4 was found to be highly selective to acetate ion over other anions. The mechanism of fluorescence was based on the anion-induced inhibition of excited-state intramolecular proton transfer (ESIPT).