Lebeau Estelle L., Adeyemi S. Ajao, Meyer Thomas J.
Department of Chemistry, CB#3290, Venable Hall, The University of North Carolina, Chapel Hill, North Carolina 27599-3290.
Inorg Chem. 1998 Dec 14;37(25):6476-6484. doi: 10.1021/ic970908z.
The complex [(tpy)(C(2)O(4))Ru(III)ORu(III)(C(2)O(4))(tpy)].8H(2)O (1.8H(2)O) (tpy is 2,2':6',2"-terpyridine) has been prepared and characterized by X-ray crystallography and FTIR, resonance Raman, and (1)H NMR spectroscopies. From the results of the X-ray analysis, angleRuORu is 148.5 degrees with a torsional angle (O(22)-Ru(2)-O(1)-Ru(1)-O(12)) of 22.7 degrees and there is a short Ru-O bridge distance of 1.843 Å. 1 undergoes a chemically reversible one-electron, pH-independent oxidation at 0.73 V vs NHE (0.49 V vs SCE) from pH = 4-8 and a pH-dependent, two-electron, chemically irreversible reduction at -0.35 V below pH = 4.0. Addition of 1.8H(2)O to strong acid generates (tpy)(H(2)O)(2)Ru(III)ORu(III)(H(2)O)(2)(tpy) (2), which has been characterized by UV-visible, resonance Raman, and (1)H NMR measurements. In pH-dependent cyclic voltammograms there is evidence for a series of redox couples interrelating oxidation states from Ru(II)ORu(II) to Ru(V)ORu(V). In contrast to the "blue dimer", cis,cis-(bpy)(2)(H(2)O)Ru(III)ORu(III)(OH(2))(bpy)(2), oxidation state Ru(IV)ORu(IV) (Ru(V)ORu(III)?) does appear as a stable oxidation state. Oxidation of Ru(IV)ORu(IV) by Ce(IV) in 0.1 M HClO(4) is followed by rapid O(2) production and appearance of an anated form of Ru(IV)ORu(IV). O(2) formation is in competition with oxidative cleavage of Ru(V)ORu(V) by Ce(IV) to give Ru(VI)(tpy)(O)(2)(OH(2)). Anation and oxidative cleavage prevent this complex from being a true catalyst for water oxidation.
已制备出配合物[(tpy)(C₂O₄)Ru(III)ORu(III)(C₂O₄)(tpy)].8H₂O (1·8H₂O)（tpy为2,2':6',2"-三联吡啶），并通过X射线晶体学、傅里叶变换红外光谱、共振拉曼光谱和¹H核磁共振光谱对其进行了表征。根据X射线分析结果，∠RuORu为148.5°，扭转角（O₂₂-Ru₂-O₁-Ru₁-O₁₂）为22.7°，且存在1.843 Å的短Ru-O桥连距离。1在相对于标准氢电极（NHE）为0.73 V（相对于饱和甘汞电极（SCE）为0.49 V）时经历化学可逆的单电子、与pH无关的氧化反应，pH范围为4至8，在pH低于4.0时，在-0.35 V发生与pH有关的双电子、化学不可逆还原反应。向强酸中加入1·8H₂O会生成[(tpy)(H₂O)₂Ru(III)ORu(III)(H₂O)₂(tpy)]⁴⁺ (2)，已通过紫外可见光谱、共振拉曼光谱和¹H核磁共振测量对其进行了表征。在与pH有关的循环伏安图中，有证据表明存在一系列将Ru(II)ORu(II)到Ru(V)ORu(V)氧化态相互关联的氧化还原对。与“蓝色二聚体”顺式、顺式-[(bpy)₂(H₂O)Ru(III)ORu(III)(OH₂)(bpy)₂]⁴⁺不同，氧化态Ru(IV)ORu(IV)（Ru(V)ORu(III)?）确实作为一种稳定的氧化态出现。在0.1 M高氯酸中，Ce(IV)将Ru(IV)ORu(IV)氧化后，会迅速产生O₂并出现Ru(IV)ORu(IV)的酰化形式。O₂的形成与Ce(IV)对Ru(V)ORu(V)的氧化裂解竞争，生成[Ru(VI)(tpy)(O)₂(OH₂)]²⁺。酰化和氧化裂解阻止了该配合物成为真正的水氧化催化剂。
