Novel fluorescein appended calix[4]arenes for preferential recognition of Cu2+ ions

Novel calix[4]arene derivatives with fluorescein appendages (7 and 8) were synthesized for application in preferential recognition of Cu2+ ions over other metal ions through enhancement of fluorescence intensity with a detection limit up to nanomolar level in acetonitrile. A profound color change from colorless to yellow in acetonitrile and colorless to purple in aqueous medium indicates specific copper ion recognition plausibly due to selective ring opening of fluorescein spirolactam functionality. The synthesized receptor shows high selectivity and reversibility required for developing efficient chemosensors for Cu2+.