Seven ruthenium catalysts with the general formula [(CNC)Ru(CH₃CN)₂Cl]OTf have been used to understand structure function relationships in the sensitized photocatalytic CO₂ reduction reaction. Herein, CNC is a pincer ligand containing imidazole‐based N‐heterocyclic carbenes (NHCs) attached to a central pyridyl ring with R groups at the 3‐ or 4‐position. Two new complexes (R = 3‐OMe, 4‐NPh₂) have been fully characterized by analytical and spectroscopic methods and single‐crystal X‐ray diffraction. Furthermore, three previously synthesized complexes (R = 4‐Me, 4‐NMe₂, and 4‐OH) are used for photocatalysis for the first time. Methoxy and methyl donor groups in the 4‐position lead to durable catalysts (TON up to 1000) with high TOFs (up to 174 h^–1) for CO production. In contrast, R = 4‐NPh₂, 3‐OMe, and 4‐H substituents lead to modest TOF values (up to 32 h^–1), yet these systems are still robust and achieve up to 565 TON. In contrast, low activity is observed with 4‐NMe₂ and 4‐OH substituents, which resemble sacrificial donors and may be leading to side reactions. Thus, remote substituents were found to greatly influence catalyst activity and longevity.

中文翻译：

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含供体基团的CNC钳在钌二氧化碳还原催化剂中的结构功能关系

通式[（CNC）Ru（CH ₃ CN）₂ Cl] OTf的七种钌催化剂已被用于理解光敏型CO ₂还原反应中的结构功能关系。在本文中，CNC是一种钳位配体，其中包含咪唑基N杂环卡宾（NHC），该碳烯连接到在3或4位带有R基团的中央吡啶基环上。两种新的络合物（R = 3-OMe，4-NPh ₂）已通过分析和光谱法以及单晶X射线衍射进行了充分表征。此外，三个先前合成的配合物（R = 4-Me，4-NMe ₂，和4-OH）首次用于光催化。4位上的甲氧基和甲基供体基团可产生持久的催化剂（TON高达1000）和高的TOF（长达174 h ^–1）用于生产CO。相比之下，R = 4-NPh _2，3 -OMe和4-H取代基会产生适度的TOF值（最高32 h ^–1），但是这些系统仍然很可靠，最高可达565 TON。相反，使用4-NMe ₂和4-OH取代基观察到的活性较低，它们类似于牺牲性供体，可能导致副反应。因此，发现远程取代基极大地影响催化剂的活性和寿命。