Enantiospecific photochromic reaction of thiophenophan-1-enes

以二（氯甲基）苯和二（巯基）二乙烯为原料，在高稀释条件下进行偶联反应，合成了二（二）乙烯-二（二硫乙烯）烷衍生物。该产物在紫外线和可见光照射下表现出光致变色特性。测定了光环化量子产率和环还原量子产率，并建立了光环化量子产率与反应碳原子间距离的关系。邻位异构体由于其固定在光活性反构象上且两个活性碳原子之间的距离较短，因此具有较高的光环化效率。研究了这些光致变色化合物的热稳定性，发现其邻位异构体具有热不可逆性。PMMA（聚甲基丙烯酸甲酯）薄膜中的光致变色[2.2]元环苯环-1-烯可逆地改变了折射率，通过椭偏分析估计了折射率。例如，PMMA薄膜（10.6%）在901.82nm处，开放态和352 nm处的折射率分别为1.4934和1.4996，变化量（Δn）为0.0062。计算得到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薄膜的折射率由于[2.2]元环苯环-1-烯的开放和封闭形式之间的光致变色反应而发生光可逆变化。

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.