Inspired by the oxygen-evolving complex in photosystem II, the nature of intermediates and the oxygen–oxygen bond formation mechanism in photocatalytic water oxidation have been the topic of current research. Herein, we report that the key intermediates and the O–O bond formation step in the catalytic water oxidation by [Ru^III(bpy)₃]³⁺ or the excited state of 2,3-dichloro-5,6-dicyano-p-benzoquinone (³DDQ∗) with a nonheme iron complex, [Fe^II(dpaq)]⁺, were captured and identified. Especially, two keyintermediates, such as an iron(V)-oxo ([Fe^V(dpaq)(O)]²⁺ or [Fe^IV(dpaq cation radical)(O)]²⁺) and an iron(III)-hydroperoxo species ([Fe^III(dpaq)(OOH)]⁺), were captured in the water oxidation reactions; [Fe^V(dpaq)(O)]²⁺ (or [Fe^IV(dpaq cation radical)(O)]²⁺) was detected using transient absorption spectroscopy in the oxidation of [Fe^IV(dpaq)(O)]⁺ by ³DDQ∗, whereas the formation of [Fe^III(dpaq)(OOH)]⁺ was directly observed by reacting [Fe^IV(dpaq)(O)]⁺ with [Ru^III(bpy)₃]³⁺ or ³DDQ∗ in the presence of water. The evolution of O₂ upon the oxidation of [Fe^III(dpaq)(OOH)]⁺ by DDQ was also demonstrated in this study.

受光系统II中的放氧络合物的启发，光催化水氧化中中间体的性质和氧-氧键形成机制一直是当前研究的主题。在此，我们报道了[Ru ^III (bpy) ₃ ] ³⁺或2,3-二氯-5,6-二氰基-p的激发态催化水氧化的关键中间体和O-O键形成步骤。捕获并鉴定了-苯醌 ( ³ DDQ*) 与非血红素铁络合物 [Fe ^II (dpaq)] ⁺ 。特别是，两种关键中间体，例如铁(V)-氧代([Fe ^V (dpaq)(O)] ²⁺或[Fe ^IV (dpaq 阳离子自由基)(O)] ²⁺ )和铁(III)-氢过氧化物 ([Fe ^III (dpaq)(OOH)] ⁺ )，在水氧化反应中被捕获； [Fe ^IV (dpaq)(O)] ²⁺（或 [Fe ^IV (dpaq 阳离子自由基)(O)] ^{2+ ) 在 [Fe IV} (dpaq)(O)] ⁺的氧化过程中使用瞬态吸收光谱法检测到通过^{3 DDQ*，而 [Fe III} (dpaq)(OOH)] ⁺的形成是通过 [Fe ^IV (dpaq)(O)] ⁺与 [Ru ^III (bpy) ₃ ] ³⁺或³ DDQ反应直接观察到的* 有水存在时。本研究还证明了 DDQ氧化 [Fe ^III (dpaq)(OOH)] ^{+时 O} ₂的演变。