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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >A mononuclear ruthenium complex showing multiple proton-coupled electron transfer toward multi-electron transfer reactions
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A mononuclear ruthenium complex showing multiple proton-coupled electron transfer toward multi-electron transfer reactions

机译：单核钌配合物，显示多质子偶联电子向多电子转移反应的转移

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摘要

Two new ruthenium(ii) complexes bearing dissociable protons, [Ru(trpy)(H _2bim)Cl]PF _6 (1) and [Ru(trpy)(H _2bim)(OH _2)](PF _6) _2 (2) (H _2bim = 2,2′-biimidazole and trpy = 2,2′:6′, 2′′-terpyridine), were synthesized and characterized, where the H _2bim and M-OH _2 moieties are expected to serve as proton-dissociation sites. Single crystal X-ray diffraction analyses revealed that the H _2bim and M-OH _2 moieties act as proton donors in intermolecular hydrogen bonds. Two pK _a values of 2 (pK _a1 = 9.0 and pK _a2 = 11.3) were spectrophotometrically determined, where the first proton dissociation is assigned to that from H 2bim and the second is from M-OH _2. This assignment was supported by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations for two sets of conjugated bases, [Ru(trpy)(Hbim)(OH _2)] ~+ and [Ru(trpy)(H _2bim)(OH)] ~+ for the first proton dissociation, and [Ru(trpy)(Hbim)(OH)] ~+ and [Ru(trpy)(bim)(OH _2)] ~+ for the second dissociation. Electrochemical studies in aqueous solutions under various pH conditions afforded the Pourbaix diagram (potential versus pH diagram) of 2, where the pK a values found from the diagram agree well with those determined spectrophotometrically. It was also found that 2 demonstrates four-step proton-coupled electron transfer (PCET) reactions to give the four-electron oxidized species, [Ru ~(IV)(trpy)(bim)(O)] ~(2+), without electrostatic charge buildup during the reactions. The multiple PCET ability of 2 would be applicable to various multi-electron oxidation reactions. Catalysis of electrochemical water oxidation was indeed evaluated in the initial attempt to demonstrate multi-electron oxidation reactions, revealing that the water oxidation potential for 2 is lower than that for other ruthenium catalysts, [Ru(trpy)(bpy)(OH _2)] ~(2+), [Ru(trpy)(bpm)(OH _2)] ~(2+) and [Ru(tmtacn)(bpy)(OH _2)] ~(2+) (bpy = 2,2′-bipyridine, bpm = 2,2′-bipyrimidine, and tmtacn = 1,4,7-trimethyl-1,4,7-triazacyclononane), which are known to be active catalysts for water oxidation.
机译：两个带有可分解质子的新钌（ii）络合物[Ru（trpy）（H _2bim）Cl] PF _6（1）和[Ru（trpy）（H _2bim）（OH _2）] [PF _6）_2（2） （H _2bim = 2,2'-联咪唑和trpy = 2,2'：6'，2''-叔吡啶）被合成和表征，其中H _2bim和M-OH _2部分有望作为质子-离解位点。单晶X射线衍射分析表明，H _2bim和M-OH _2部分在分子间氢键中充当质子供体。用分光光度法确定了两个pK _a值为2（pK _a1 = 9.0和pK _a2 = 11.3），其中第一个质子离解与H 2bim缔合，第二个质子离解与M-OH _2缔合。两组共轭碱基[Ru（trpy）（Hbim）（OH _2）]〜+和[Ru]的密度泛函理论（DFT）和时变密度泛函理论（TD-DFT）计算支持该分配。 （trpy）（H _2bim）（OH）]〜+用于第一次质子解离，[Ru（trpy）（Hbim）（OH）]〜+和[Ru（trpy）（bim）（OH _2）]〜+对于第二个解离。在各种pH条件下在水溶液中进行的电化学研究得出的Pourbaix图（电势与pH图）为2，其中从该图发现的pKA值与通过分光光度法测定的值相吻合。还发现2证明了四步质子偶联电子转移（PCET）反应产生了四电子氧化物种[Ru〜（IV）（trpy）（bim）（O）]〜（2+），反应期间不会积聚静电荷。 2的多重PCET能力将适用于各种多电子氧化反应。实际上，在最初尝试证明多电子氧化反应的过程中确实评估了电化学水氧化的催化作用，结果表明2的水氧化电位低于其他钌催化剂[Ru（trpy）（bpy）（OH _2）]的水氧化电位。 〜（2 +），[Ru（trpy）（bpm）（OH _2）]〜（2+）和[Ru（tmtacn）（bpy）（OH _2）]〜（2+）（bpy = 2,2' -bipyridine，bpm = 2,2'-bipyrimidine和tmtacn = 1,4,7-trimethyl-1,4,7-triazacyclononane），它们是水氧化的活性催化剂。

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