Fan Suju, Lam Yintung, He Liang, Xin John H
Institute of Textiles & Clothing, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
Shenzhen Research Institute, The Hong Kong Polytechnic University, Shenzhen, People's Republic of China.
R Soc Open Sci. 2022 Jun 8;9(6):211894. doi: 10.1098/rsos.211894. eCollection 2022 Jun.
Symmetrical azobenzene derivatives with two catechol groups, 1d-4d, were synthesized as kinds of novel compounds, and the structures were confirmed using mass spectrometry and nuclear magnetic resonance spectroscopy. These compounds could attain photostationary state rapidly in solution upon UV irradiation, and their photochromism had good reversibility. Substituents and their positions on azobenzene chromophore had obvious influence on the maximum absorption and photochromic performances of these as-synthesized compounds. Electron-donating group on positions could contribute to the redshift π-π* band. The sulfonamide group that is bonded to dopamine molecules and azobenzene rings caused a negligible n-π* transition of isomer, resulting in photobleaching upon UV irradiation. Among the four compounds, 4d had the strongest electron-donating -methoxy substituents and lower planarity; thus its absorption could decrease more significantly upon UV irradiation of the same intensity, and its -to- conversion could be up to 63%. Furthermore, owing to the presence of catechol groups, 4d showed an effective affinity and adhesion to substrate, and on the surface of substrate, a weak colour change could be observed upon UV irradiation, but the reversibility was poorer than that in solution.
合成了具有两个儿茶酚基团的对称偶氮苯衍生物1d - 4d作为新型化合物，并通过质谱和核磁共振光谱对其结构进行了确证。这些化合物在紫外光照射下能在溶液中迅速达到光稳态，且其光致变色具有良好的可逆性。偶氮苯发色团上的取代基及其位置对这些合成化合物的最大吸收和光致变色性能有明显影响。对位上的供电子基团有助于π - π带发生红移。与多巴胺分子和偶氮苯环相连的磺酰胺基团导致反式异构体的n - π跃迁可忽略不计，从而在紫外光照射下发生光漂白。在这四种化合物中，4d具有最强的供电子甲氧基取代基且平面性较低；因此，在相同强度的紫外光照射下，其吸收下降更为显著，其反式到顺式的转化率可达63%。此外，由于儿茶酚基团的存在，4d对底物表现出有效的亲和力和附着力，在底物表面，紫外光照射时可观察到微弱的颜色变化，但其可逆性比在溶液中差。
