Selective and efficient catalytic two-electron two-proton (2e^–/2H⁺) reduction of dioxygen (O₂) to hydrogen peroxide (H₂O₂) has been achieved less successfully than four-electron four-proton (4e^–/4H⁺) reduction of O₂ because of the instability of the H₂O₂ product in the presence of metal catalysts. We report herein a highly efficient 2e^–/2H⁺ reduction of O₂ by ferrocene (Fc; one-electron reductant) and 9,10-dihydro-10-methylacridine (AcrH₂; two-electron reductant and an NADH analog), with a cobalt corrole complex, [Co^III(tpfc)(Py)₂] (1), in the presence of HClO₄ in CH₃CN at 298 K, affording a large TON (50,000) and a high turnover frequency (275 s^–1) with 100% selectivity in producing H₂O₂. The H₂O₂ product yielded in the 2e^–/2H⁺ reduction of O₂ using AcrH₂ as a reductant was stable for more than 5 h even in the presence of 1. Detailed kinetic analysis revealed that the rate-determining step (rds) for the 2e^–/2H⁺ reduction of O₂ by Fc with 1 in the presence of HClO₄ in CH₃CN was the proton-coupled electron transfer from Co^III(tpfc) (2) to O₂ to produce a cobalt(III) corrole radical cation, [Co^III(tpfc^•+)]⁺ (3), which was detected by EPR. When ferrocene was replaced by AcrH₂, the rds became the electron transfer from AcrH₂ to 3, coupled with the deprotonation of AcrH₂^•+ (ET/PT), followed by fast ET from AcrH^• to 3. To the best of our knowledge, this is a report of a highly efficient Co-corrole catalyst that retains its cobalt(III) oxidation state for the 2e^–/2H⁺ reduction of O₂ in producing H₂O₂ with a high selectivity.

中文翻译：

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钴钴配合物高效催化双电子双质子化将双氧还原为过氧化氢

与四电子四质子（4e ^– / 4H ）相比，成功实现了选择性和高效的催化双电子二质子（2e ^– / 2H ⁺）将双氧（O ₂）还原为过氧化氢（H ₂ O ₂）的成功。⁺）减少的O ₂，因为H的不稳定的₂ ö ₂产物在金属催化剂存在下进行。我们在这里报告了由二茂铁（Fc；单电子还原剂）和9,10-二氢-10-甲基ac啶（AcrH ₂）对O ₂的高效2e ^– / 2H ⁺还原; 双电子还原剂和NADH类似物），并在HClO ₄存在下于298 K的CH ₃ CN中，存在钴钴络合物[Co ^III（tpfc）（Py）₂ ]（1）。50,000）和高周转频率（275 s ^–1），在生产H ₂ O _2时具有100％的选择性。使用AcrH ₂作为还原剂，在2e ^– / 2H ⁺的O ₂还原中生成的H ₂ O ₂产物即使在存在1的条件下也能稳定5小时以上。。详细的动力学分析表明，该速率决定步骤（RDS）为2E ^- / 2H ⁺还原的O- ₂通过FC与1中的HClO的存在₄在CH ₃ CN是从Co质子偶联的电子传递^III（TPFC ）（2）到O ₂生成钴（III）钴自由基阳离子，[Co ^III（tpfc ^•+）] ⁺（3），由EPR检测。当二茂铁被AcrH ₂取代时，rds成为电子从AcrH ₂转移到3，再加上AcrH ₂ ^•+（ET / PT）的去质子作用，然后是从AcrH ^•到3的快速ET 。据我们所知，这是一份高效的Co-corole催化剂的报告，该催化剂保留了钴（II​​I）的氧化态，可在高选择性生产H ₂ O _2时以2e ^– / 2H ⁺还原O ₂。