Enantiospecific photochromic reaction of thiophenophan-1-enes

在高稀释条件下，通过双（氯甲基）苯与双（巯基甲基）二噻吩基乙烯的偶联反应，合成了由二噻吩基乙烯和苯桥组成的双硫杂（二噻吩基乙烯）芳衍生物。产物在紫外光和可见光照射下表现出光致变色性能。测定了苯环化和环化反转的量子产率，并建立了苯环化量子产率与苯环上活性碳原子间距的关系。邻位异构体由于其固定在光活性反构象和两个活性碳原子之间的短距离而在光环化中具有高效率。研究了这些光致变色化合物的热稳定性，发现邻位异构体具有热不可逆性，光致变色[2.2]间环番-1-烯在聚甲基丙烯酸甲酯（PMMA）膜中可逆地改变了折射率，这是通过椭圆偏振分析估算的。例如，PMMA薄膜（10.6%）在352 nm处的开放态和光稳态的折射率在901.82 nm处分别为1.4934和1.4996，变化量（Δn）为0.0062。计算的开放和封闭形式的折射率分别为1.744和1.859。含有光致变色染料的PMMA膜的折射率由于[2.2]间环番-1-烯的开放和封闭形式之间的光致变色反应而光可逆地改变。

Dithia-(dithienylethena)phane derivatives, composed of dithienylethene moieties and benzene bridges, were synthesized by a coupling reaction of the corresponding bis(chloromethyl)benzene with bis(mercaptomethyl)dithienylethene under high-dilution conditions. The products exhibit photochromic properties upon irradiation with ultraviolet and visible light. The photocyclization and cycloreversion quantum yields were determined, and a relationship between the photocyclization quantum yield and distance between the reactive carbon atoms of the phane derivatives established. The ortho isomer has a high efficiency in photocyclization due to its fixation in the photo-active anti conformation and short distance between the two reactive carbon atoms. The thermal stability of these photochromic compounds has been studied and the ortho isomer found to show thermal irreversibility.Photochromic [2.2]metacyclophan-1-ene in a PMMA (polymethylmethacryate) film reversibly changed the refractive index, which was estimated by ellipsometric analysis. For example, the refractive indexes of the open form and the photostationary state at 352 nm in PMMA films (10.6%) were 1.4934 and 1.4996 at 901.82nm, respectively, and the variation (Δn) was 0.0062. The calculated refractive indexes of the open and closed forms were 1.744 and 1.859, respectively. The refractive index of the PMMA film containing a photochromic dye changed photoreversibly due the photochromic reaction between the open and closed forms of [2.2]metacyclophan-1-ene.