Significant advances during the past decades in the design and studies of Ru complexes with polypyridine ligands have led to the great development of molecular water oxidation catalysts and understanding on the O−O bond formation mechanisms. Here we report a Ru-based molecular water oxidation catalyst [Ru(bds)(pic)₂] (Ru-bds; bds²⁻ = 2,2′-bipyridine-6,6′-disulfonate) containing a tetradentate, dianionic sulfonate ligand at the equatorial position and two 4-picoline ligands at the axial positions. This Ru-bds catalyst electrochemically catalyzes water oxidation with turnover frequencies (TOF) of 160 and 12,900 s⁻¹ under acidic and neutral conditions respectively, showing much better performance than the state-of-art Ru-bda catalyst. Density functional theory calculations reveal that (i) under acidic conditions, the high valent Ru intermediate Ru^V=O featuring the 7-coordination configuration is involved in the O−O bond formation step; (ii) under neutral conditions, the seven-coordinate Ru^IV=O triggers the O−O bond formation; (iii) in both cases, the I2M (interaction of two M−O units) pathway is dominant over the WNA (water nucleophilic attack) pathway.

在过去几十年中，具有聚吡啶配体的Ru配合物的设计和研究取得了重大进展，这导致了分子水氧化催化剂的巨大发展以及对O-O键形成机理的理解。在这里，我们报告了一种基于Ru的分子水氧化催化剂[Ru（bds）（pic）₂ ]（Ru-bds； bds ²⁻ = 2,2'-联吡啶-6,6'-二磺酸盐），其中含有四齿双阴离子磺酸盐在赤道位置的配体和在轴向位置的两个4-甲基吡啶配体。该Ru-bds催化剂以电化学方式催化水氧化，其周转频率（TOF）为160和12,900 s ^-1分别在酸性和中性条件下显示出比现有的Ru-bda催化剂更好的性能。密度泛函理论计算表明：（i）在酸性条件下，具有7位配位构型的高价Ru中间体Ru ^V = O参与了O-O键的形成步骤；（ii）在中性条件下，七坐标Ru ^IV = O触发O-O键的形成；（iii）在这两种情况下，I2M（两个M-O单元的相互作用）途径都比WNA（水亲核攻击）途径更重要。