Insight into triphenylamine and coumarin serving as copper (II) sensors with "OFF" strategy and for bio-imaging in living cells.

Chemosensing is one of the widest and powerful techniques for response to anions and cations in living systems serving as bio-probes. Meanwhile, copper(II) (Cu(II)) widely exists in the environment and the human body as a common trace element, which plays an necessary role in most physiological processes. Thus, it is extremely urgent to explore means for effective, rapid and convenient detection of Cu(II) in living cells. Herein, we introduce a novel strategy for designing triphenylamine (TS) and coumarin-based (CS) functional sensors for Cu(II) detection with fluorescence "OFF" switching mechanism by blocking intramolecular charge transfer (ICT). Based on this design strategy, we have demonstrated two kinds of fluorophores sensors with aunique new fluorescent dye and excellent photophysical properties, which have shown rapid recognition of Cu(II) via a stoichiometric ratio of 2:1 and the proposed binding mode was confirmed by the single-crystal structure of CS-Cu(II) complex. In addition, we have carried out density functional theory (DFT) calculation with the B3LYP exchange functional employing RB3LYP/6-31G basis sets to get insight into the mechanism of Cu(II)-sensors alongside their optical properties. Furthermore, the sensors were capable of bio-imaging Cu(II) in living cancer cells (HepG2, A549 and Hela) with low cytotoxicity and good biocompatibility shown. Taken together, We expect that this novel strategy would provide new insight into the development of Cu(II) detection techniques and could be used more for biomedical applications.