The oxidation of organic substrates is of fundamental importance in nature and includes key transformations in organic synthesis and industry. Dioxygen (O₂) is potentially the greenest oxidant because O₂ is available in air and its reduction product is water, which is environmentally the most benign substance. However, the direct thermal oxidation of organic substrates with O₂ is spin-forbidden because the spin state of ground-state O₂ is triplet and the spin state of most organic substrates is singlet. Transition metal complexes can react with triplet O₂ in the presence of an electron source to produce metal–oxygen intermediates, such as metal-oxo and metal-hydroperoxo complexes, that can oxidize substrates under mild conditions. Various thermal and photocatalytic mechanisms of the oxidation of organic substrates by O₂ with transition metal complexes have been critically discussed by focusing on how metal–oxygen intermediates are produced in the presence of an electron source and then react with organic substrates. Metal–oxygen intermediates are more easily produced by the reactions of metal complexes with hydrogen peroxide (H₂O₂) and act as active catalysts for the oxidation of substrates by H₂O₂. The photocatalytic oxidation of water by O₂ to produce H₂O₂ has been combined with the catalytic oxidation of organic substrates by H₂O₂ to achieve the photocatalytic oxidation of organic substrates by O₂. The photocatalytic oxidation of organic substrates by O₂ with the use of water as an electron source has also been made possible by the use of inorganic and organic photocatalysts, which can be combined with transition metal complexes as catalysts for thermal reaction steps.

中文翻译：

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以水为电子源的双氧热和光催化氧化有机底物

有机底物的氧化本质上具有根本的重要性，包括有机合成和工业中的关键转变。氧气（O ₂）可能是最绿色的氧化剂，因为空气中有O ₂，其还原产物是水，这是环境上最有益的物质。然而，由于基态O ₂的自旋态为三重态且大多数有机基板的自旋态为单重态，因此禁止使用O ₂对有机基板进行直接热氧化。过渡金属络合物可以与三重态O ₂反应在电子源的存在下产生金属-氧中间体，例如金属-氧代和金属-氢过氧配合物，它们可以在温和的条件下氧化底物。通过重点讨论在电子源存在下如何生成金属-氧中间体，然后使其与有机底物发生反应的方法，对用O ₂与过渡金属配合物氧化有机底物的各种热催化机理和光催化机理进行了严格的讨论。金属-氧中间体更容易被金属配合物与过氧化氢（H的反应中产生的₂ ö ₂），并且作为底物的氧化活性的催化剂用H ₂ ö ₂。O ₂对水的光催化氧化生成H ₂ ö ₂已结合由H有机底物的催化氧化₂ ö ₂被O，实现有机基质的光催化氧化₂。通过使用无机和有机光催化剂，还可以使用水作为电子源通过O ₂对有机底物进行光催化氧化，所述无机和有机光催化剂可以与过渡金属配合物结合用作热反应步骤的催化剂。