Mechanochemical reactivity of a multimodal 2H-bis-naphthopyran mechanophore
Mechanochemical reactivity of a multimodal 2H-bis-naphthopyran mechanophore
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DOI：
10.1039/d3py00344b
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发表时间：
2023-05-10
影响因子：
4.6
通讯作者：
Robb, Maxwell J.
中科院分区：
文献类型：
--
作者：
Osler, Skylar K.;McFadden, Molly E.;Robb, Maxwell J.
在机械力作用下反应产生具有独特耦合吸收特性的离散产物态的多模态机械基团是力传感聚合物设计的有趣目标。在此，我们研究了2h -双萘吡喃机械载体的反应性，该机械载体在溶液中使用超声波机械激活产生热持久的单merocyanine和双merocyanine产物，不同于光化学产生的热可逆产物。我们证明了力介导的酯C(O)-O键断裂反应在环打开后建立了分子内氢键，锁定了一个开放形式的merocyanine亚基。模型化合物研究表明，这种锁定的亚基对在另一个亚基上有反式外环烯烃的双merocyanine异构体具有显著的热稳定性，这意味着作为机械化学激活的产物，形成了一种不寻常的反式merocyanine异构体。密度泛函理论计算意外地预测了双merocyanine物种的热可逆反环化反应，这可以解释不寻常的反merocyanine异构体的机械化学生成。
Multimodal mechanophores that react under mechanical force to produce discrete product states with uniquely coupled absorption properties are interesting targets for the design of force-sensing polymers. Herein, we investigate the reactivity of a 2H-bis-naphthopyran mechanophore that generates thermally persistent mono-merocyanine and bis-merocyanine products upon mechanical activation in solution using ultrasonication, distinct from the thermally reversible products generated photochemically. We demonstrate that a force-mediated ester C(O)-O bond scission reaction following ring opening establishes an intramolecular hydrogen bond, locking one merocyanine subunit in the open form. Model compound studies suggest that this locked subunit confers remarkable thermal stability to bis-merocyanine isomers possessing a trans exocyclic alkene on the other subunit, implicating the formation of an unusual trans merocyanine isomer as the product of mechanochemical activation. Density functional theory calculations unexpectedly predict a thermally reversible retro-cyclization reaction of the bis-merocyanine species that could explain the mechanochemical generation of the unusual trans merocyanine isomer.