A dual‐function chemosensor based on coumarin for fluorescent turn‐on recognition of Hg2+ and colorimetric detection of Cu2+ in aqueous media

Abstract

A novel coumarin derivative CTT was synthesized via the condensation of 7‐(N,N‐diethylamino) coumarin‐3‐aldehyde with 5‐amino‐1,3,4‐thiadiazole‐2‐thiol and its structure was characterized using infrared spectroscopy (IR), 1H NMR, mass spectrometry (MS) techniques, and elemental analysis. The recognition properties of CTT with metal ions were investigated in CH3CN–H2O (v/v = 1/1) solution using UV–vis absorption and fluorescence emission spectrum method. The results showed that CTT could monitor Cu2+ and Hg2+ simultaneously as a dual‐function chemosensor in CH3CN–H2O (v/v = 1/1). CTT could be used to detect Cu2+ colorimetrically; when using CTT, a color change from yellowish‐brown to yellowish‐green could be readily observed by the naked eye. CTT showed turn‐on fluorescent recognition of Hg2+, the fluorescence enhancement was attributed to the inhibited C=N isomerization and the obstructed excited state intramolecular proton transfer (ESIPT) of CTT. The recognition mechanism of CTT for Cu2+ and Hg2+ was studied by experiments and theoretical calculations, respectively. Therefore, CTT has the ability to be a “single chemosensor for dual targets.”