Design And Function Of Photochromic Naphthopyran-Benzimidazole Fluorescent Switches

In recent years,the attentions and studies on Naphthopyrans and derivatives are not only their photochromic properties but also the applications in high and new technology fields, especially optical information storage, photochromic decorations,optical switches and so on.Three new fluorescent switches based on fluorophore benzimidazole and photochromic naphthopyran have been designed and synthesized with different spaces between benzimidazole and naphthopyran. The emission intensity of benzimidazole can be modulated between “on” and “off” via the photochromic reaction of naphthopyran, which indicates that the synthesized compounds possess the property of fluorescent photoswitching.The molecular structures of three optical switches were well characterized by the means of NMR and MS spectra. The studies on their absorbance spectra proved that three compounds have excellent photochromic performance in solutions and films.The results of the fluorescent spectra demonstrated that the fluorescence of benzimidazole could be quenched by the open-form naphthopyran, the photoinduced energy transfer from excited benzimidazole to naphthopyran was responsible for the fluorescent quenching. The reversible modulation of fluorescence for several cycles proved the potential applications of the synthesized compounds in fluorescence photoswitching. Furthermore, the quenched extents of their emission are related to chemical bond between photochromic naphthopyran and benzimidazole. The shorter the space, the larger the quenched extent.