Thiourea as a Template for Photodimerization of Azastilbenes,Journal of the American Chemical Society

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Thiourea as a Template for Photodimerization of Azastilbenes
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2010-09-29 , DOI: 10.1021/ja105166d
Balakrishna R. Bhogala ₁ , Burjor Captain ₁ , Anand Parthasarathy ₁ , V. Ramamurthy ₁

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In this study we have explored the potential of thiourea (TU) as a template to preorient stilbazoles and bispyridylethylenes (azastilbenes) in the crystalline state. TU is able to preorient eleven azastilbenes toward dimerization in the crystalline state. While cocrystals of these eleven olefins photodimerized to a single dimer expected based on crystal packing, pure crystals of these olefins either were nonreactive or gave a mixture of dimers. The differential photobehavior of the pure crystals and cocrystals highlights the importance of TU in templating the olefins in a photoreactive orientation in the crystalline state. X-ray crystallographic and photochemical studies have identified a few azastilbenes that photodimerize in spite of not being arranged in an ideal orientation in the crystalline state. These as well as a few examples already reported in the literature suggest that it is important to recognize that molecules could experience large amplitude motions in the crystalline state, especially when energized by light. Short-term lattice instability caused by photoexcitation can be effective in driving a photochemical reaction. Thus one should view the crystalline arrangement of molecules upon light exposure as "dynamic" rather than "static" as determined from X-ray structure analysis.

中文翻译：

硫脲作为氮二苯乙烯光二聚化的模板

在这项研究中，我们探索了硫脲 (TU) 作为模板在结晶状态下预定向 stilbazoles 和双吡啶基乙烯 (azastilbenes) 的潜力。TU 能够将 11 种氮杂二苯乙烯预先定向为结晶状态的二聚化。虽然这 11 种烯烃的共晶体光二聚化为基于晶体堆积预期的单一二聚体，但这些烯烃的纯晶体要么是非反应性的，要么是二聚体的混合物。纯晶体和共晶体的不同光行为突出了 TU 在将烯烃模板化为结晶状态的光反应取向中的重要性。X 射线晶体学和光化学研究已经确定了一些氮杂二苯乙烯，尽管在结晶状态下没有以理想的取向排列。这些以及文献中已经报道的一些例子表明，重要的是要认识到分子可以在结晶状态下经历大幅度的运动，尤其是在受光激励时。由光激发引起的短期晶格不稳定性可以有效地驱动光化学反应。因此，应该将曝光时分子的晶体排列视为“动态”而不是根据 X 射线结构分析确定的“静态”。

更新日期：2010-09-29

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