Synthesis Of Novel Nonsymmetric Photochromic Diarylethenes And Investigation On Their Spectra Properties

Diarylethenes have so far been shown to be one of the most promising materials in realizing the development of photo-mode data storage and molecule switches having photochromic characteristics, because of their thermal stability, high fatigue resistance, and very rapid response time. Many efforts have been made to study in detail the diarylethene class, including molecular design principle, synthesis, their properties, and so on.In the present dissertation, we have designed eleven nonsymmetric molecule, 1-(2-methyl-5-phenylthiophen-3-yl)-2-(2-methyl-5-(R-phenyl)thiophene-3-yl)perfluorocyclopentene (R=-p-fluoro, m-fluoro, o-fluoro, p-methyl, m-methyl, m-trifluoromethyl, 3-thienyl) and 1-(2, 5-dimethyl)-2-[2-methyl-5-(R-phenyl)thiophene-3-yl]perfluorocyclopentene(R=-p-methoxy, p-eth -oxy, p-chloro), and characterized by NMR, IR, UV-Vis spectra, et al. Four single crystal samples of the diarylethenes were prepared and analyzed by X-ray crystallography.Their optoelectronic properties, such as UV-Vis spectra, fluorescence spectra, thermal irreversibility, fatigue resistance and electrochemical properties were investigated in solution, crystalline state, and on PMMA films. They all showed good photochromic properties and gave strong fluorescence. Both the maximum emission and absorption wavelength of the diarylethenes in PMMA were longer than that of them in solutions. In addition, solvent effect and photochemical reaction kinetics of diarylethenes were also investigated. Diarylethenes showed positive solvent effect which the maximum wavelength is increased with the enhance of solvent polarity. When the intensity of the irradiation light is constant, the cyclization and cyclorevsion reaction belonged to zero and first order reaction, respectively. When the aryl groups are thiophene rings, which have low aromatic stabilization energies, the closed-ring isomers are thermally stable and can not return to the open-ring form isomers. Their fatigue resistance can be measured by irradiation with UV and Vis light by turns. The results showed that they have good fatigue resistance. Finally, the electrochemical properties of diarylethene were investigated in acetonitrile. It was found that the oxidation potentials of opening-ring state are all higher than those of closed-ring state because of the extent of π-conjugation in the closed-ring isomers.