Abstract：
Cyclic amino(alkyl) and cyclic amino(aryl) carbenes (cAACs/cAArCs) have been established as very useful ligands for catalytic and photonic applications of transition metal complexes. Herein, we describe the synthesis of a structurally related sterically demanding, electrophilic [2.2]isoindolinophanyl-based carbene (iPC) with a [2.2]paracyclophane moiety. The latter leads to more delocalized frontier orbitals and intense green fluorescence of (HiPC)OTf (2) from an intra-ligand charge transfer (1ILCT) state in the solid state. Base-promoted synthesis of the free carbene led to an unusual ring expansion and subsequent dimerization reaction, but the beneficial ligand properties can be exploited by trapping in situ at a metal center. The iPC ligand is a very potent π-chromophore, which participates in low energy metal-to-ligand (ML)CT transitions in [RhCl(CO)2(iPC)] (4) and IL-\"through-space\"-CT transitions in [Au(iPC)2]OTf (5). The steric demand of the iPC leads to high stability of 5 against air, moisture, or solvent attack, and ultralong-lived green phosphorescence with a lifetime of 185 μs is observed in solution. The beneficial photophysical and electronic properties of the iPC ligand, including a large accessible π surface area, were exploited by employing highly efficient energy transfer (EnT) photocatalysis in a [2+2] styrene cycloaddition reaction using 5, which outperformed other established photocatalysts in comparison.
摘要：
环氨基（烷基）和环氨基（芳基）卡宾（cAACs/cAArCs）已被确定为过渡金属配合物的催化和光子应用的非常有用的配体。在这里，我们描述了一种结构相关的空间要求的合成，亲电子[2.2]异吲哚基碳烯（iPC），具有[2.2]对环烷部分。后者导致更多的离域前沿轨道和（HiPC）OTf（2）在固态下从配体内电荷转移（1ILCT）状态产生强烈的绿色荧光。游离卡宾的碱促进合成导致不寻常的环膨胀和随后的二聚反应，但有益的配体性质可以通过在金属中心原位捕获来利用。iPC配体是一种非常有效的π-发色团，参与[RhCl（CO）2（iPC）]（4）中的低能金属-配体（ML）CT跃迁和[Au（iPC）2]OTf（5）中的IL-“通过空间”-CT跃迁。iPC的空间需求导致5对空气的高稳定性，水分,或溶剂攻击，在溶液中观察到寿命为185μs的超长寿命绿色磷光。iPC配体的有益光物理和电子性质，包括一个大的可接近的π表面积，通过在使用5的[22]苯乙烯环加成反应中采用高效能量转移（EnT）光催化来开发，相比之下，其性能优于其他已建立的光催化剂。
