Improving Fatigue Resistance of Dihydropyrene by Encapsulation within a Coordination Cage
Improving Fatigue Resistance of Dihydropyrene by Encapsulation within a Coordination Cage
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DOI：
10.1021/jacs.0c06146
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发表时间：
2020-08-26
影响因子：
15
通讯作者：
Klajn, Rafal
中科院分区：
文献类型：
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作者：
Canton, Martina;Grommet, Angela B.;Klajn, Rafal
光致变色分子在不同波长的光照射下发生可逆异构化，这是一个可以改变其物理和化学性质的过程。例如，二氢芘（DHP）是一种深色化合物，在可见光照射下异构化为浅棕色的环番二烯（CPD）。CPD然后可以在用UV光照射或在黑暗中加热时异构化回DHP。DHP和CPD之间的转化被认为是通过双自由基中间体进行的;涉及这种不稳定中间体的双分子事件因此导致快速分解和差的循环性能。在这里，我们表明，DHP的可逆异构化可以稳定后，限制在（PdIIL 4）-L-6协调笼。通过使用笼保护该反应性中间体，每个异构化反应进行到更高的产率，这显著降低了系统在重复光循环时经历的疲劳。虽然已知分子限制有助于稳定反应性物质，但这种效应通常不用于保护反应性中间体，从而提高反应产率。我们设想，在限制下进行反应将不仅改善光致变色分子的环状性能，而且还可以增加可从传统的低产率有机反应获得的产物的量。
Photochromic molecules undergo reversible isomerization upon irradiation with light at different wavelengths, a process that can alter their physical and chemical properties. For instance, dihydropyrene (DHP) is a deep-colored compound that isomerizes to light-brown cyclophanediene (CPD) upon irradiation with visible light. CPD can then isomerize back to DHP upon irradiation with UV light or thermally in the dark. Conversion between DHP and CPD is thought to proceed via a biradical intermediate; bimolecular events involving this unstable intermediate thus result in rapid decomposition and poor cycling performance. Here, we show that the reversible isomerization of DHP can be stabilized upon confinement within a (PdIIL4)-L-6 coordination cage. By protecting this reactive intermediate using the cage, each isomerization reaction proceeds to higher yield, which significantly decreases the fatigue experienced by the system upon repeated photocycling. Although molecular confinement is known to help stabilize reactive species, this effect is not typically employed to protect reactive intermediates and thus improve reaction yields. We envisage that performing reactions under confinement will not only improve the cyclic performance of photochromic molecules, but may also increase the amount of product obtainable from traditionally low-yielding organic reactions.