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Abstract The development of near-infrared (NIR) photochromic materials, particularly activated by visible light, are of increasing interest for their potential application in photoresponsive optoelectronics and functional bio-materials. Here, a novel D-DTE-A type dithienylethene NDB , which was modified by difluoroboron β-diketonate (BF 2 bdk) and dimethylphenylamine (DMPA) moieties, has been developed. It exhibited solvent-dependent photophysical properties before irradiation, and the visible light-triggered NIR photochromic behavior with solvent-dependent features was only observed in Toluene. Moreover, it displayed intense fluorescent turn-on acid-sensing properties in less polar solvent [Toluene, Dichloromethane (DCM) and Ethyl acetate (EA)] through the blockage of photoinduced electron transfer (PET) effect. Specially, NDB with photochromic inactivity in DCM could perform a unique gated photochromism in the presence of TFA/TEA. Graphical abstract Image 1 Highlights • A novel D-A type dithienylethene modified by BF 2 bdk moiety was developed. • It exhibited solvent-dependent photophysical properties before irradiation. • Solvent-dependent and vis light-triggered NIR photochromism was observed. • It displayed fluorescent turn-on acid-sensing properties in less polar solvent. [ABSTRACT FROM AUTHOR]

Dithienylethenes 1 and 2 , consisting of three photochromic units linked by imidazole bridges, together with its N-methylated derivatives 3 and 4 , have been synthesized. Their photochromic properties and fluorescence behaviors have also been investigated in solution by irradiation with various wavelengths of UV light. It was found that the dithienylethene 1 showed selective photochromism, indicated by the fluorescence change upon irradiation with 365 nm and 302 nm light. However, dithienylethenes 2 , 3 and 4 only underwent a photocyclization reaction in the middle switchable unit under the same conditions. Moreover, for dithienylethenes 2 and 4 , introduction of fluorine atoms on the cyclopentene evidently enhanced the photochromic properties compared with perhydro-substituted dithienylethenes 1 and 3 . And dithienylethene 3 could act as one potential fluorescent molecular switch. [ABSTRACT FROM AUTHOR]