Geometric and electronic structure of a crystallographically characterized thiolate-ligated binuclear peroxo-bridged cobalt(III) complex
Geometric and electronic structure of a crystallographically characterized thiolate-ligated binuclear peroxo-bridged cobalt(III) complex
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DOI：
10.1007/s00775-019-01686-x
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发表时间：
2019-09-01
影响因子：
3
通讯作者：
Kovacs, Julie A.
中科院分区：
文献类型：
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作者：
Dedushko, Maksym A.;Schweitzer, Dirk;Kovacs, Julie A.
为了阐明O-O键断裂的金属依赖机制及其微观反转，我们在此比较了O-2衍生的双核Co（III）-和Mn（III）-过氧化合物的电子和几何结构。双核金属过氧配合物提出形成作为中间体在锰促进光合H2O氧化，和一个含钴的人工叶的灵感来自自然的光合H2O氧化催化剂。一个非常活跃的过氧的晶体学表征是可能的工作与替代惰性，低自旋钴（III）。密度泛函理论（DFT）计算表明，前线轨道的钴（III）-过氧化合物明显不同于类似的锰（III）-过氧化合物。与Co（III）-过氧相关的最高占据分子轨道（HOMO）更多地位于反键π *（O-O）轨道中的过氧上，而结构类似的Mn（III）-过氧的HOMO在金属d-轨道和过氧π *（O-O）轨道上都是离域的。对于低自旋d（6）Co（III），填充的t（2g）轨道阻止了双占据反键π *（O-O）轨道对金属离子的π反馈。这与高自旋d（4）Mn（III）的情况不同，因为这些轨道是半填充的。相对于后者，这削弱了前者的过氧O-O键。
In order to shed light on metal-dependent mechanisms for O-O bond cleavage, and its microscopic reverse, we compare herein the electronic and geometric structures of O-2-derived binuclear Co(III)- and Mn(III)-peroxo compounds. Binuclear metal peroxo complexes are proposed to form as intermediates during Mn-promoted photosynthetic H2O oxidation, and a Co-containing artificial leaf inspired by nature's photosynthetic H2O oxidation catalyst. Crystallographic characterization of an extremely activated peroxo is made possible by working with substitution-inert, low-spin Co(III). Density functional theory (DFT) calculations show that the frontier orbitals of the Co(III)-peroxo compound differ noticeably from the analogous Mn(III)-peroxo compound. The highest occupied molecular orbital (HOMO) associated with the Co(III)-peroxo is more localized on the peroxo in an antibonding pi*(O-O) orbital, whereas the HOMO of the structurally analogous Mn(III)-peroxo is delocalized over both the metal d-orbitals and peroxo pi*(O-O) orbital. With low-spin d(6) Co(III), filled t(2g) orbitals prevent pi-back-donation from the doubly occupied antibonding pi*(O-O) orbital onto the metal ion. This is not the case with high-spin d(4) Mn(III), since these orbitals are half-filled. This weakens the peroxo O-O bond of the former relative to the latter.