A new class of photoswitchable NHC ligands, named azImBA, has been developed by integrating azobenzene into a previously unreported imidazobenzoxazol-1-ylidene framework. These rigid photochromic carbenes enable precise control over confinement around a metal’s coordination sphere. As a model system, gold(I) complexes of these NHCs exhibit efficient bidirectional E–Z isomerization under visible light, offering a versatile platform for reversibly photomodulating the reactivity of organogold species. Comprehensive kinetic studies of the protodeauration reaction reveal rate differences of up to 2 orders of magnitude between the E and Z isomers of the NHCs, resulting in a quasi-complete visible-light-gated ON/OFF switchable system. Such a high level of photomodulation efficiency is unprecedented for gold complexes, challenging the current state-of-the-art in photoswitchable organometallics. Thorough investigations into the ligand properties paired with structure–reactivity correlations underscored the unique ligand’s steric features as a key factor for reactivity. This effective photocontrol strategy was further validated in gold(I) catalysis, enabling in situ photoswitching of catalytic activity in the intramolecular hydroalkoxylation and -amination of alkynes. Given the significance of these findings and its potential as a widely applicable, easily customizable photoswitchable ancillary ligand platform, azImBA is poised to stimulate the development of adaptive, multifunctional metal complexes.

中文翻译：

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偶氮苯集成 NHC 配体：可见光可切换金属催化的多功能平台

通过将偶氮苯整合到先前未报道的咪唑并苯并恶唑-1-亚基框架中，开发出了一类新型光开关 NHC 配体，名为 azImBA。这些刚性光致变色卡宾能够精确控制金属配位球周围的限制。作为模型系统，这些 NHC 的金 (I) 配合物在可见光下表现出高效的双向E - Z异构化，为可逆光调节有机金物质的反应性提供了一个多功能平台。原脱环反应的综合动力学研究揭示了 NHC 的E和Z异构体之间高达 2 个数量级的速率差异，从而形成了准完整的可见光门控开/关可切换系统。如此高水平的光调制效率对于金配合物来说是前所未有的，挑战了当前光可切换有机金属的最先进水平。对配体特性与结构-反应性相关性的深入研究强调了独特配体的空间特征是反应性的关键因素。这种有效的光控制策略在金（I）催化中得到了进一步验证，能够在炔烃的分子内加氢烷氧基化和氨基化中实现催化活性的原位光切换。鉴于这些发现的重要性及其作为广泛适用、易于定制的光开关辅助配体平台的潜力，azImBA 有望刺激适应性多功能金属配合物的开发。