A highly selective “turn-on” fluorescent probe for detecting Cu2+ in two different sensing mechanisms

A new coumarin-derived hydrazone (1) has been developed as a “turn-on” fluorescent probe for the detection of Cu2+ in two different sensing mechanisms. In anhydrous acetonitrile, the strong fluorescence response of 1 to Cu2+ was mainly attributed to the chelation-controlled C=N isomerization. Besides, S-donor is indispensable in protecting from the Cu2+-induced fluorescence quenching. In aqueous acetonitrile, 1 as a chemodosimeter can highly selectively sense of Cu2+, which was ascribed to the Cu2+-promoted cyclization reaction affording the strong fluorescent cyclization product (2). The proposed cyclization reaction was confirmed by the single-crystal structure of 2. Furthermore, 1 was utilized for imaging intracellular Cu2+ with good performance.