Macrocyclic photochromic molecules incorporating multiple photochromic units are known to exhibit cooperative and nonlinear photochromic reactions among distinct photochromic components. While extensive research has concentrated on positive photochromic molecules, this study presents a pioneering attempt in synthesizing macrocyclic photochromic molecules that integrate negative photochromic units. Binaphthyl-bridged phenoxyl imidazolyl radical complex, BN-PIC, exhibits unique negative photochromism in which the thermally stable colored isomer converts to the metastable colorless isomer via a short-lived biradical upon visible-light irradiation. Macrocyclic biphotochromic molecules incorporating two BN-PIC units were synthesized and the effects of ring strain on the photochromic properties including the photoconversion efficiencies and the rates of the thermal reverse reaction were investigated. The photokinetic study of these macrocyclic biphotochromic molecules demonstrated that the structural distortion of the ring caused by the isomerization of one photochromic unit significantly influenced the photoisomerization efficiency and the rate of the thermal reverse reaction of the other photochromic unit.

中文翻译：

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包含两个负光致变色单元的大环的逐步光致变色


已知包含多个光致变色单元的大环光致变色分子在不同的光致变色组分之间表现出协同和非线性光致变色反应。虽然广泛的研究集中在正性光致变色分子上，但这项研究提出了合成集成负性光致变色单元的大环光致变色分子的开创性尝试。联萘桥苯氧基咪唑基自由基络合物 BN-PIC 表现出独特的负光致变色性，其中热稳定的有色异构体在可见光照射下通过短寿命的双自由基转化为亚稳态无色异构体。合成了包含两个 BN-PIC 单元的大环双光致变色分子，并研究了环应变对光致变色性能（包括光转换效率和热逆反应速率）的影响。这些大环双光致变色分子的光动力学研究表明，一个光致变色单元异构化引起的环结构变形显着影响另一个光致变色单元的光异构化效率和热逆反应速率。