One-electron reduced photosensitizers have been invoked as crucial intermediates in photoredox catalysis, including multiphoton excitation and electrophotocatalytic processes. However, such reduced chromophores have been less investigated, limiting mechanistic studies of their associated electron transfer processes. Here, we report a total of 11 different examples of isolable singly reduced iridium chromophores. Chemical reduction of a cyclometalated iridium complex with potassium graphite affords a 19-electron species. Structural and spectroscopic characterizations reveal a ligand-centered reduction product. The reduced chromophore absorbs a wide range of light from ultraviolet to near-infrared and exhibits photoinduced bimolecular electron transfer reactivity. These studies shed light on elusive reduced iridium chromophores in both ground and excited states, providing opportunities to investigate a commonly invoked intermediate in photoredox catalysis.

中文翻译：

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单还原铱发色团：合成、表征和光化学

单电子还原光敏剂已被用作光氧化还原催化中的关键中间体，包括多光子激发和电光催化过程。然而，这种还原发色团的研究较少，限制了对其相关电子转移过程的机理研究。在这里，我们报告了总共 11 个不同的可分离单还原铱发色团的例子。环金属化铱配合物与钾石墨的化学还原提供了 19 电子物质。结构和光谱表征揭示了以配体为中心的还原产物。还原的生色团吸收从紫外线到近红外的各种光，并表现出光诱导的双分子电子转移反应性。