The Multiple Switch System Based On The Diarylethene Dimer And The Nitrogenous Diarylethene

Diarylethene compounds under irradiation of UV and white light alternately, can change between open-ring and closed-ring isomers. With the change of the molecule structure, photochemical and photophysical properties of the compounds will change. Thus, these two isomers of having different photochemical and photophysical properties can form a switching system under light stimulation. Diarylethene of comprising two photochromic diarylethene units is called diarylethene dimer, a asymmetric diarylethene dimer theoretically may form four isomers under light stimulation, it is possible to construct multiple switche system, but actually, it can not always get four isomers. Since nucleophilicity of the nitrogen atom, the diarylethene containing a nitrogen atom, not only can respond to light, but also can have a response on metal ions, and therefore can also constructe multiple switches.In this paper, six kinds of new diarylethene dimer molecules, three diarylethene isomers containing a pyridine ring and a diarylethene containing a benzene ring were synthesized, and were identificated through NMR, IR and elemental analysis in structure. Switching process of six kinds of diarylethene dimers under irradiation of ultraviolet and white light was deeply studied. And It also was studied that nitrogen atom position effect of three kinds of diarylethene isomers containing a pyridine ring. The main results were summarized as follows:The diarylethene dimmers DT-1-4were synthesized, compound DT-1could occur light reaction when it was irradiated by UV or white light in acetonitrile solution, and can not return to the initial state. UV absorption spectrum changes and fluorescence spectrum changes of DT-1in acetonitrile solution had the same switching process. Three diarylethene dimer compounds DT-2-4could also undergo photochromic reaction in acetonitrile solution. There was the same switch of UV absorption and fluorescent emission between DT-2and DT-1. Compounds DT-3and DT-4only had one photochromic product, their photochromic properties were same with the monomer diarylethene.Diarylethene dimer DT-5was synthesized, which had only one photochromic product under UV irradiation. Extending the irradiation time and reducing the ultraviolet wavelength of light could not get more photochromic products, and therefore its photochromic properties could be studied with the method the monomer diarylethene. The cyclization quantum yield of compound DT-5was greater than that of the monomer diarylethene, and the cycloreversion quantum yield of compound DT-5was lower than that of the monomer diarylethene, this result was because of the the existence of the photochromic group with imidazole as the bridge unit which is not active under UV irradiation.The solution of compound DT-5could be regulated by pH, and addtion trifluoroacetic acid to the solution of the closed-ring isomer of DT-5can result in blue shift of absorption peak, accompanying with solution color from violet to purple red. Addtion trifluoroacetic acid to the solution of the open-ring isomer of DT-5could make the fluorescence of solution enhancement and in this moment the solution emit blue fluorescence. The open-ring isomer and closed-ring isomer of DT-5did not have fluorescent switching performance, but addtion trifluoroacetic acid to the solution of the open-ring isomer of DT-5could activate its fluorescent switching performance. Compound DT-5can be regulated acid/base and ultraviolet/white light circularly, and therefore it could structure a multiple switching system. In addition, I had synthesized compound DT-6, and it had similar UV and fluorescence switching performance with DT-5.Compounds DT-7-10were synthesized, and existence of pyridine ring and the nitrogen atom position had a huge impact on the optical properties of diarylethene. The compound DT-7had the maximum cyclization quantum yield and the compound DT-9had the minimum cyclization quantum yield and cycloreversion quantum yield. Comparing with the cyclization quantum yield and cycloreversion quantum yield of DT-10with a benzene ring, the cyclization quantum yields of compounds DT-7-10, had no large change, but the cycloreversion quantum yields of compounds DT-7-10were greatly improved. Compounds DT-7-9not only could response to light stimulation, but also could response to the pH. Under UV irradiation, compounds DT-7-9all changed to orange red, and after adding the acid, the absorption peaks of closed isomers of compounds DT-7and DT-9’s red shift, but the absorption peak of closed isomer of compound DT-8blue shift. By simultaneously light and acid-base regulation, multi-switch system of DT-7-9could be built. Compounds DT-7-9had great potential to be used as a fluorescent switch material. Under the UV light, the fluorescence quenching rate of compounds DT-7-9in the PMMA is greater than that in hexane solution. Fluorescence emission spectrums of the open-ring isomers of compounds DT-7-9have a certain order, in which the fluorescence emission intensity of compound DT-8o is the lowest and the fluorescence emission intensity of compound DT-9o is the highest, but were all lower than the fluorescence emission intensity of compound DT-10o with a benzene.