A reaction-based, colorimetric and near-infrared fluorescent probe for Cu2+ and its applications

A reaction-based near-infrared (NIR) fluorescent probe, (E)-4-(2-(4-(dicyanometh- ylene)-4H-chromen-2-yl)vinyl)phenyl picolinate (DCM-P), was designed and synthesized by employing the dicyanomethylene-4H-pyran chromophore as the fluorophore and the 2-picolinic ester group as the recognition unit. The proposed probe DCM-P showed significant NIR fluorescence “turn-on” response to Cu2+ with distinct colorimetric change from yellow to purple. The recognition mechanism of probe for Cu2+ was confirmed by fluorescence spectroscopy, 1H NMR spectra, HRMS spectrometry and TD-DFT calculations. The probe possesses the advantages of large Stokes shift (116 nm), applicability in physiological conditions, low detection limit (2.3 × 10−8 M), and high selectivity toward Cu2+ in presence of other metal ions. Encouraged by these desirable properties, the probe DCM-P was successfully used for quantitative determination of Cu2+ in real water samples and NIR fluorescence imaging of Cu2+ in living cells with satisfactory results.