A coumarin-derived useful scaffold exhibiting Cu2+ induced fluorescence quenching and fluoride sensing (On-Off-On) via copper displacement approach

Abstract

Some coumarin-thiazole based molecular scaffolds/probes have been designed and synthesized. The photophysical behavior of probes and their interaction with metal ions and anions have been examined through the absorption and fluorescence spectroscopy in different medium. Probe 6 showed good optical behavior in acetonitrile and upon interaction with different metal ions and anions displayed strong fluorescence quenching (∼87%; switch-Off) with Cu2+ while remained silent toward the tested anions, respectively. Moreover, 6-Cu2+ ensemble when tested toward different anions only fluoride (F-) enable copper displacement (as CuF2) and led to fluorescence enhancement (switched-On). Probe 6 has selectively detected Cu2+ in real water sample, and on cellulose paper strips. Additionally, the naked eye sensitive "On-Off-On" sensing behavior of 6 mimics the function of a sequential logic circuit at molecular level. The FTIR, NMR (1H and 13C), and ESI-MS spectroscopy supported the proposed mechanism of interaction. © 2014 Elsevier B.V. All rights reserved.