New highly selective turn-on fluorescence receptor for the detection of copper (II)

Three new receptors (la-c) bearing a p-dimethylaminobenzamide fluorophore have been synthesized and evaluated in terms of their fluoroionophoric properties towards various metal ions. Notably, receptors la and is exhibited dramatic fluorescent enhancement towards Cu2+ in acetonitrile. Subsequent investigations revealed that the highly selective behavior of these receptors towards Cu2+ could be attributed to the Cu2+-mediated oxidative cyclization of these compounds to the corresponding 1,3,4-oxadiazoles. Solvent effects and quantum calculations indicated that 1a and 1c both possessed an intramolecular charge transfer channel, which could be obstructed by the oxidative cyclization of these receptors. Receptor la was successfully applied to the determination of the Cu2+ in drug sample with a low detection limit of 22 x 10(-8) mol L-1. (C) 2016 Elsevier B.V. All rights reserved.