Research On A Class Of Fluorescent Photochromic Compound With A Benzo[b]Thiophene-1,1-dioxide Bridge

The photochromic diarylethenes compounds, because of its excellent fatigue resistance, high fatigue resistance and high signal contrast, are widely used in material, chemical, biological and other scientific fields. Generally speaking, diarylethane derivatives have no fluorescence, or weak emission in their open forms, but the fluorescence is a more sensitive detection signal, therefore, exploring and developing a new type of photochromic diarylethylene compounds with fluorescent property, is a more and more important research direction.A fluorescent photochromic matrix compound TM1 with a benzo[b]thiophene-1,1-dioxide bridge and its derivatives TM2-TM4 were synthesized. In order to study TM1-TM4, we choose a reference compound BTF6 (with a perfluorocyclopentene brige), and investigate their spectral properties in ethyl acetate solution. The photochromic reaction of TM1-TM4 respond to more thoroughly than BTF6, performance in the cyclization conversions of TM1-TM4 are higher than BTF6, which of TM4 is even up to 0.86. Meanwhile, the fatigue resistence of TM1 (Fatigue time=1800 min) is superior to that of BTF6 (Fatigue time=1500 min), and a film of TM1 in poly (methyl methacrylate) (PMMA) matrix was prepared, and the result demonstrate a good photochromic behavior of TM1 in polyer film. Most important of all, the closed-forms of TM1-TM4 have distinct fluorescent emission at 577 nm (493 nm excitation),597 nm (375 nm excitation),579 nm (473 nm excitation) and 601 nm (370 nm excitation), respectively, while closed-form of BTF6(c-BTF6) has no emission. And the maximum emission wavelength of c-TM2 and c-TM4 is shift to red (20 nm and 24 nm, respectively), compared to that of c-TM1. Fluorescence quantum yield of c-TM2 (0.005) is highest in the closed-forms maye originates from its relatively high fluorescence lifetime (2.242 ns). And fluorescence quantum yield of o-TM1 is highest in the open-forms, which is higher than o-BTF6 (0.002). Cell experiments demonstrate that TM3 can enter the MCF-7 cell, and has a good fluorescence signal, which shows that this kind of compounds has a good potential in cell imaging and the super resolution imaging applications. The phosphorescence spectra of open-forms of TM1-TM4 and o-BTF6 have a big difference before and after deoxygenation, which proved that open-forms of TM1-TM4 all have a triplet state, like o-BTF6. All these research results make a firm foundation on the further research of fluorescent photochromic compound with a benzo[b]thiophene-1,1-dioxide bridge.