Cyclotriguaiacylene has been functionalised with 3- or 4-pyridyl-azo-phenyl groups to form a series of molecular hosts with three azobenzene-type groups that exhibit reversible photo-isomerisation. Reaction of the host molecules with [Ir(C^N)₂(NCMe)₂]⁺ where C^N is the cyclometallating 2-phenylpyridinato, 2-(4-methylphenyl)pyridinato or 2-(4,5,6-trifluorophenyl)pyridinato results in the self-assembly of a family of five different [{Ir(C^N)₂}₃(L)₂]³⁺ coordination cages. Photo-irradiation of each of the cages with a high energy laser results in E → Z photo-isomerisation of the pyridyl-azo-phenyl groups with up to 40% of groups isomerising. Isomerisation can be reversed by exposure to blue light. Thus, the cages show reversible structure-switching while maintaining their compositional integrity. This represents the largest photo-induced structural change yet reported for a structurally-integral component of a coordination cage. Energy minimised molecular models indicate a switched cage has a smaller internal space than the initial all-E isomer. The [Ir(C^N)₂(NCMe)₂]⁺ cages are weakly emissive, each with a deep blue luminescence at ca. 450 nm.

中文翻译：

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具有光异构化偶氮芳香族连接基的结构转换 M3L2 Ir(iii) 配位笼†‡

环三愈创木已被 3- 或 4-吡啶基-偶氮-苯基官能化，形成一系列具有三个偶氮苯型基团的分子主体，这些基团表现出可逆的光异构化。主体分子与 [Ir(C^N) ₂ (NCMe) ₂ ] ⁺的反应，其中 C^N 是环金属化 2-苯基吡啶基、2-(4-甲基苯基)吡啶基或 2-(4,5,6-三氟苯基) )pyridinato 导致五个不同的 [{Ir(C^N) ₂ } ₃ (L) ₂ ] ³⁺配位笼家族的自组装。用高能激光对每个笼子进行光照射，导致吡啶基偶氮苯基基团发生E → Z光异构化，其中异构化率高达 40%。暴露于蓝光下可以逆转异构化。因此，笼子表现出可逆的结构转换，同时保持其成分完整性。这代表了迄今为止报道的配位笼结构整体组件中最大的光诱导结构变化。能量最小化分子模型表明，开关笼具有比初始全E异构体更小的内部空间。[Ir(C^N) ₂ (NCMe) ₂ ] ⁺笼具有弱发射性，每个笼子在约100° C处发出深蓝色发光。450 纳米。