Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 03760, Korea.
Graduate School of Science and Engineering, Meijo University, Nagoya, Aichi, 468-8502, Japan.
ChemSusChem. 2019 Sep 6;12(17):3931-3940. doi: 10.1002/cssc.201901276. Epub 2019 Jul 25.
Water (H O) is the most environmentally benign reductant and is oxidized to evolve dioxygen (O )-the greenest oxidant-in photosystem II. This Minireview focuses on photocatalytic oxygenation of substrates with H O as an oxygen source and O as an oxidant. Metal complexes can be oxidized by two molecules of one-electron oxidants with H O to produce high-valent metal-oxo complexes, which act as active oxidants for oxygenating organic substrates. When an appropriate oxidant is employed for the substrate oxidation, the reduced oxidant can be oxidized by dioxygen to regenerate the oxidant when water and dioxygen are used as an oxygen source and an oxidant, respectively. Photoinduced electron transfer from a substrate (S) to the excited state of complex [(L)M ] produces a substrate radical cation (S ), accompanied by the regeneration of [(L)M ]. S then reacts with H O to produce an OH adduct radical that is oxidized by [(L)M ] to yield an oxygenated product (SO), in which the oxygen atom originates from H O, accompanied by regeneration of [(L)M ]. Photocatalytic oxidation of H O by O to produce H O is combined with the catalytic oxygenation of substrates with H O to produce the oxygenated products, in which the oxygen atom originates from O at the beginning but later from water. This Minireview provides a promising strategy for oxygenation of substrates by using H O as an oxygen source and O as the greenest oxidant.
水（H₂O）是最环保的还原剂，它在光系统 II 中被氧化为释放出氧气（O₂）——最绿色的氧化剂。本篇综述聚焦于以 H₂O 作为氧源和 O₂作为氧化剂的底物光催化氧化。金属配合物可以被两分子单电子氧化剂氧化，产生高价金属氧配合物，后者可作为氧化有机底物的活性氧化剂。当使用合适的氧化剂进行底物氧化时，当水和氧气分别作为氧源和氧化剂时，还原态氧化剂可以被氧气氧化，从而再生氧化剂。当底物（S）向配合物[(L)M]的激发态进行光诱导电子转移时，产生底物自由基阳离子（Sₙ⁺），同时[(L)M]再生。然后，S 与 H₂O 反应生成 OH 加合物自由基，该自由基被[(L)M]氧化，生成含氧产物（SO），其中氧原子来自 H₂O，同时再生[(L)M]。O₂通过光催化氧化 H₂O 产生 H₂O，与 H₂O 催化氧化底物相结合，生成含氧产物，其中氧原子最初来自 O₂，但随后来自水。本篇综述为以 H₂O 作为氧源、O₂作为最绿色氧化剂的底物氧化提供了一种很有前景的策略。
