Study on the photochromism, photochromic fluorescence switch, fluorescent and colorimetric sensing for Cu of naphthopyran-diaminomaleonitrile dyad and recognition Cu in living cells.

A well-designed naphthopyran-diaminomaleonitrile dyad (sensor 1) has been synthesized successfully, its molecular structure was well characterized by NMR and mass spectrometry. Sensor 1 exhibits excellent photochromic and photochromic fluorescence switch performance with reversible color change and good fatigue resistance upon alternating ultraviolet irradiation and thermal bleaching. In addition, sensor 1 displayed excellent fluorescent and colorimetric sensing ability towards Cu ions with high selectivity and sensitivity. The addition of 5.0 equiv. of Cu ions into sensor 1 (1 × 10) in CHCN solution significantly quenched the fluorescence of sensor 1 by 80.0%. Furthermore, the addition of Cu ions also caused the complete disappearance of the absorbance band at 350-450 nm in absorbance spectra of sensor 1 and accompanied by the distinct color change form yellow to colorless. Job's plot, mass spectrometry, H NMR titration and DFT calculations proved that sensing performance was attributed to the formation of 1:1 sensor 1-Cucomplexes. Sensor 1 can monitor the existence of Cu ions in living cells via the fluorescence images. Sensor 1 showed great potential applications as chemosensor and photochromic materials.