Small molecule photoswitches capable of toggling between two distinct molecular states in response to light are versatile tools to monitor biological processes, control photochemistry, and design smart materials. In this work, six novel dicyanorhodanine-based pyrrole-containing photoswitches are reported. The molecular design avails both the Z and E isomers from synthesis, where each can be isolated using chromatographic techniques. Inter- and intramolecular hydrogen bonding (H-bonding) interactions available to the E and Z isomers, respectively, uniquely impart thermal stability to each isomer over long time periods. Photoisomerization could be assessed by solution NMR and UV–vis spectroscopic techniques along with complementary ground- and excited-state computational studies, which show good agreement. Quantitative E → Z isomerization occurs upon 523 nm irradiation of the parent compound (where R = H) in solution, whereas Z → E isomerization using 404 nm irradiation offers a photostationary state (PSS) ratio of 84/16 (E/Z). Extending the π-conjugation of the pyrrole unit (where R = p-C₆H₄–OMe) pushes the maximum absorption to the yellow-orange region of the visible spectrum and allows bidirectional quantitative isomerization with 404 and 595 nm excitation. Comparator molecules have been prepared to report how the presence or absence of H-bonding affects the photoswitching behavior. Finally, studies of the photoswitches in neat films and photoinactive polymer matrices reveal distinctive structural and optical properties of the Z and E isomers and ultimately afford reversible photoswitching to spectrally unique PSSs using visible light sources including the Sun.

中文翻译：

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用于溶液和固态中可见光驱动定量光开关的二氰基罗丹宁-吡咯缀合物

小分子光电开关能够响应光在两种不同的分子状态之间切换，是监测生物过程、控制光化学和设计智能材料的多功能工具。在这项工作中，报道了六种新型的基于二氰基罗丹宁的含吡咯的光开关。分子设计利用了合成中的Z和E异构体，其中每种异构体都可以使用色谱技术分离。E和Z异构体分别具有分子间和分子内氢键（H 键）相互作用，独特地赋予每种异构体长期的热稳定性。光异构化可以通过溶液核磁共振和紫外可见光谱技术以及互补的基态和激发态计算研究来评估，结果显示出良好的一致性。溶液中母体化合物（其中R = H）在 523 nm 照射下发生定量E → Z异构化，而使用 404 nm 照射的Z → E异构化提供 84/16 ( E / Z )的光稳态 (PSS) 比率。扩展吡咯单元的 π 共轭（其中R = p -C ₆ H ₄ –OMe）将最大吸收推至可见光谱的黄橙色区域，并允许在 404 和 595 nm 激发下进行双向定量异构化。已准备好比较分子来报告氢键的存在或不存在如何影响光开关行为。最后，对纯薄膜和光惰性聚合物基质中的光开关的研究揭示了Z和E异构体独特的结构和光学特性，并最终使用包括太阳在内的可见光源为光谱独特的 PSS 提供可逆光开关。