| Photochromic functional materials undergo reversible conversion between two isomers by absorbing light within a specific wavelength range,which is accompanied by changes in the optical and chemical properties of the material.Diarylethene compounds have attracted much attention because of their excellent fatigue resistance,thermal stability and high potential for structural modification.Turn-on fluorescent diarylethenes,which turn fluorescence on and off when changing from their open-ring to closed-ring isomers,can meet the requirements of many imaging applications where requires initial dark background.As we all know highenergy ultraviolet light can harm to biological group and high precision equipment,and the traditional diarylethene photochromic materials often require the ultraviolet light for triggering.In this dissertation,the visible light-driven photochromic molecules were successfully prepared by modifying Ph-BTTO4 with dimethylamine groups and methoxy groups as donors,and the influence of the donor groups on photochromic properties of the synthesized molecules when they were attached to different sites on the benzene ring of Ph-BTTO4 was systematically investigated.The main contents of the study are summarized as follows:(1)Synthesis of reference molecules: The Br-BTTO4 was first synthesized using thiophene as an ethylene bridge with two benzothiophene 1,1-dioxides to form a central hexatriene unit.The reference molecule Ph-BTTO4 was successfully synthesized by replacing the bromine atom on Br-BTTO4 with a benzene ring using a new synthetic method,and used for comparison with the D-A type molecules where the electron-giving groups are introduced on the benzene ring.(2)Study on D-A type diarylethene molecules with single donor attached at different site: Molecules with dimethylamine(DMA)group and BTTO4 on the benzene ring at o-,inter-and p-positions were designed and successfully synthesized.The experiments have shown that all photochromic molecules with dimethylamine groups modification can be triggered with visible light,and the change on molecular energy bandgap is the smallest,when the dimethylamine group is linked at p-position.The strongest electron-giving effect and the most obvious charge transfer were found when the dimethylamine group was para-substituted,so the cycloreversion reaction was suppressed in the ring-closed state of the molecule.The gated photochromic function of DMA-p-BTTO4 was demonstrated with trifluoroacetic acid and triethylamine,taking the advantage of that dimethylamine can participate in acid-base equilibrium reactions.(3)Synthesis and study of D-A type diarylethene molecules with multiple donors attached at different position: To overcome the above phenomenon of the cycloreversion reaction suppression caused by the strong CT,methoxy groups with moderate electron-giving properties were used as the donor groups in this work.The molecules were designed by attaching methoxy group and BTTO4 to the benzene ring through the sites of 3,4,3,4,5,and 2,5,and the photophysical properties of synthesized molecules were studied.The experimental results show that the methoxy group substituted molecules can reach at least 20 photochromic cycles and have good fatigue resistance and thermal stability.It has been verified that those molecules are more photostable with visible light driving than UV light driving.The 2,5-DMPhBTTO4 was used to formulate the anti-counterfeiting ink,and inkjet printed on filter paper to form designed patterns.The molecules in the open-ring state were invisible to the naked eye,then became colored and fluorescence after conversion to the closed-ring state,demonstrating the potential of these materials for anti-counterfeiting applications. |
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