A Ru-bda Complex with a Dangling Carboxylate Group: Synthesis and Electrochemical Properties,Inorganic Chemistry

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A Ru-bda Complex with a Dangling Carboxylate Group: Synthesis and Electrochemical Properties
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-03-10 , DOI: 10.1021/acs.inorgchem.9b03595
Abolfazl Ghaderian _{1,

2} , Jan Holub ₁ , Jordi Benet-Buchholz ₁ , Antoni Llobet _{1,

3} , Carolina Gimbert-Suriñach ₁

Affiliation

Ruthenium complexes containing the tetradentate 2,2′-bipyridine-6,6′-dicarboxylato (bda^2–) equatorial ligand and ortho-subsituted pyridines in the axial position have been prepared and characterized using spectroscopic, crystallographic and electrochemical techniques. Complexes [Ru(Hbda)(DMSO)(pyC)] (1) and [Ru(bda)(DMSO)(pyA)] (2) (where pyC is 2-pyridinecarboxylate, pyA is pyridine-2-ylmethanol and DMSO is dimethyl sulfoxide) have been isolated in moderate to high yields. The solid state structures of (1-H)⁻ and 2 reveal the strong chelate effect of the axial pyridine ligand that coordinates in a bidentate fashion leaving the bda^2– equatorial ligand coordinating in a tridentate mode. In solution, compound 2 shows a dynamic equilibrium between different coordination modes of the bda^2– and pyA ligands. This phenomenon does not occur for 1 because the carboxylate binds stronger than the labile alcohol in 2. Cyclic voltammetry analysis of 1 reveals a complex behavior with a pH-independent wave at E_1/2 = 1.12 V that is tentatively associated with the two-electron Ru^IV/II couple. In sharp contrast, complex 2 shows a pH-dependent one-electron wave at E_1/2 = 0.83 V (pH 1), assigned to the proton-coupled electron transfer process of the Ru^III/II couple and a pH-independent wave at E_1/2 = 1.06 V assigned to the Ru^IV/III couple. Compound 2 is used to prepare complex [Ru(bda)(pic)(pyA)] (4). This complex is air sensitive and converts to complex [Ru(bda)(pic)(pyE)] (5) (where pyE is methyl 2-pyridine carboxylate) in the presence of methanol. This oxidation also occurs by applying a positive potential to an aqueous solution of 4, producing the derivative [Ru(bda)(pic)(pyC)] (3). Cyclic voltammetry of 3 shows two pH-independent one-electron oxidation waves at E_1/2 = 0.64 V and E_1/2 = 1.0 V, corresponding to the Ru^III/II and Ru^IV/III couples, respectively. In addition, a water oxidation catalytic wave appears at E_onset ≈ 1.4 V. Foot-of-the-wave analysis of this catalytic wave based on a water nucleophilic attack accounts for a TOF_max = 0.63–0.74 s^–1.

中文翻译：

具有悬挂羧酸盐基团的Ru-bda配合物：合成和电化学性质

制备了在轴向位置上含有四齿2,2'-联吡啶-6,6'-二羧基（bda ^2-）赤道配体和邻位取代吡啶的钌配合物，并使用光谱，晶体学和电化学技术对其进行了表征。配合物[Ru（Hbda）（DMSO）（pyC）]（1）和[Ru（bda）（DMSO）（pyA）]（2）（其中pyC是2-吡啶羧酸酯，pyA是吡啶-2-基甲醇，而DMSO是二甲基亚砜）已以中等至高收率分离出来。（1 -H）^-和2的固态结构揭示了轴向吡啶配体的强螯合作用，该配体以双齿形式配位，离开bda ^2–赤道配体以三齿模式进行配位。在溶液中，化合物2在bda ^2–和pyA配体的不同配位模式之间显示出动态平衡。这种现象不会对发生1，因为羧酸盐结合比在不稳定的醇更强2。的循环伏安法分析1揭示了与pH无关的波复杂行为ë _1/2 = 1.12信息v暂定与两个电子孺相关^{IV / II}的夫妇。与之形成鲜明对比的是，络合物2在E _1/2处显示了pH依赖的单电子波= 0.83 V（pH 1），分配给Ru ^{III / II}对的质子耦合电子传递过程，将E _1/2 = 1.06 V的不依赖pH的波分配给Ru ^{IV / III}对。化合物2用于制备复合物[Ru（bda）（pic）（pyA）]（4）。该络合物对空气敏感，并在甲醇存在下转化为络合物[Ru（bda）（pic）（pyE）]（5）（其中pyE为2-吡啶甲酸甲酯）。通过在4的水溶液上施加正电势，还会生成衍生物[Ru（bda）（pic）（pyC）]（3），也会发生这种氧化。循环伏安法3图1显示了在E _1/2 = 0.64 V和E _1/2 = 1.0 V时的两个与pH无关的单电子氧化波，分别对应于Ru ^{III / II}和Ru ^{IV / III对}。另外，水的氧化催化波出现在ê_发病基于水亲核攻击该催化波的≈1.4 V.足的最波分析占了TOF_最大= 0.63-0.74小号^-1。

更新日期：2020-03-10

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