Basic study of photochemistry of photochromic molecules

1. 二乙烯基的光致变色反应研究了二乙烯基顺式-1,2-二氰-1,2-二（2,4,5-三甲基-3-噻吩基）乙烯（化合物1）和2,3-二（2,4,5-三甲基-3-噻吩基）马来酸酐（化合物2）的光致变色反应。(1)根据紫外光照射前后的紫外可见吸收光谱，证实化合物1在花生酸和花生酯甲酯混合LB膜中具有高效的光致变色反应。(2)采用半经验分子轨道法MOPAC优化了二乙烯基的基态和激发态构象。同时计算了共形体间的势垒高度和电荷分布。从S_1态的大偶极现象解释了光致变色反应效率与聚合物（或溶剂）极性的关系。(3)在低极性、低玻璃化温度的聚合物基体中，化合物2的光致变色反应效率高。化合物1的光致变色反应效率不受聚合物种类的影响。(4)制备了二亚乙烯的胶体溶液和非晶膜，并研究了它们的光致变色反应效率。化合物1的胶体溶液具有与其己烷溶液一样高的效率。然而，由于能量在固相中发生了从开环到闭环的转移，紫外辐照后效率很快下降。化合物2的多晶或胶体溶液均未发生光致变色反应。另一方面，化合物2的一小部分非晶态薄膜被紫外照射着色。菁染料的光致变色反应非极性溶剂中的反离子影响菁染料光致异构体的寿命。对某些染料的影响很大。可见吸收波长和荧光最大值也受到反离子的影响。半经验分子轨道计算阐明了反作用的机理。少

1. Photochromic reactions of diarylethenesPhotochromic reactions of diarylethenes, cis-1,2-dicyano-1,2-bis (2,4,5-trimethyl-3-thienyl) ethene (Compound 1) and 2,3-bis (2,4,5-trimethyl-3-thienyl) maleic anhydride (Compound 2) were studied. (1) Photochromic reaction with high efficiency was confirmed for compound 1 in mixed LB films of arachidic acid and methyl arachidate on the basis o UV-visible absorption spectra before and after UV irradiation. (2) Conformations of the ground states and excited states of diarylethenes were optimized by a semiempirical molecular orbital method, MOPAC.Barrier heights between conformeres and charge distributions were also calculated. The dependence of photochromic reaction efficiency on polymer (or solvent) polarity was explained in terms of large dipolemoment in the S_1 state. (3) It was found that photochromic reaction efficiency of Compound 2 is high in a polymer matrix with low polarity and low glass-transformation temperature. Photochromic reaction … More efficiency of Compound 1 was not significantly affected by the kind of polymer. (4) Colloidal solutions and amorphous films of diarylethenes were formed and their efficiency of photochromic reactions was studied. Colloidal solution of Compound 1 has an efficiency as high as its hexane solution. However the efficiency was dropped soon after UV irradiation started, because energy transfer from ring-opened form to ring-closed form occurs in solid phase. No photochromic reactions were observed for polycrystal or colloidal solution of Compound 2. On the other hand, a little part of amorphous films of Comopund 2 was colored by UV irradiation.2. Photochromic reactins of cyanine dyesCounterions in a non-polar solvent affect lifetimes of photoisomer of cyanine dyes. The Influence was large for some kinds of dyes. Wavelengths of visible absorption and fluorescence maxima also were affected by counterions. Semiempirical molecular orbital calculations clarified the mechanism of the counterion effects. Less