Study on fluorescent switching of naphthopyran with carbazole and pyrene dyad immobilized on SBA-15

Study on the photochromism, photochromic fluorescence switch, fluorescent and colorimetric sensing for Cu2+ of naphthopyran-diaminomaleonitrile dyad and recognition Cu2+ 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 Cu²⁺ ions with high selectivity and sensitivity. The addition of 5.0 equiv. of Cu²⁺ ions into sensor 1 (1 × 10^-5) in CH₃CN solution significantly quenched the fluorescence of sensor 1 by 80.0%. Furthermore, the addition of Cu²⁺ 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, ¹H NMR titration and DFT calculations proved that sensing performance was attributed to the formation of 1:1 sensor 1-Cu²⁺complexes. Sensor 1 can monitor the existence of Cu²⁺ ions in living cells via the fluorescence images. Sensor 1 showed great potential applications as chemosensor and photochromic materials.