Synthesis And Properties Of Photochromic Fluorescent Photoswitching

The term “photochromism” indicates the photoinduced and reversiblephoto-transformation of a chemical species between two forms (A and B) havingdifferent absorption spectra. Nowadays, the number of publications onphotochromism has increased exponentially and, eventually, this area has evolved intoa mature and active research field.A naphthopyran-bridge-benzimidazole dyad which exhibits both fluorescenceand photochromism was synthesized and its fluorescence photoswitching wasinvestigated. Firstly, the target compound was characterized by1H NMR, IR, MS,crystal structure, and so on. Secondly, irradiation with365nm light induces theisomerization of the naphthopyran component to the corresponding merocyanine. Thefluorescence of the dyad was switched reversibly between on and off upon UVirradiation and thermal bleaching of the naphthopyran. Thirdly, using ultravioletillumination a pattern was created on a polymethylmethacrylate doped film with thedyad. The high-degree fluorescence photoswitching feature indicates that NP-PBI is apromising candidate in erasable optical information technology. Finally, themeasurement of redox potentials by cyclic voltammetry combined with electronicspectra and a molecular energy diagram of the individual naphthopyran andbenzimidazole demonstrated that the transformation of naphthopyran induced energyand electron transfer from the fluorescent benzimidazole to the photochromicnaphthopyran, a feature which was also supported by our DFT calculations.