具有类似于环金属化铱 (III) 化合物的电子激发态结构的钴 (III) 卡宾配合物,Journal of the American Chemical Society

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具有类似于环金属化铱 (III) 化合物的电子激发态结构的钴 (III) 卡宾配合物
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2022-05-27 , DOI: 10.1021/jacs.2c02592
Narayan Sinha ₁ , Björn Pfund ₁ , Christina Wegeberg ₁ , Alessandro Prescimone ₂ , Oliver S Wenger ₁

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许多有机金属铱 (III) 配合物具有光活性激发态，具有混合金属到配体和配体内电荷转移 (MLCT/ILCT) 特性，这为光物理学和光化学中的众多应用奠定了基础。具有类似 MLCT 激发态特性的钴 (III) 配合物似乎尚不清楚，尽管铱 (III) 和钴 (III)由于它们密切的化学关系可以采用相同的低自旋 d ^{6价电子构型。}使用刚性三齿螯合配体 (L ^CNC )，其中一个中央酰胺 π 供体两侧是两个 σ 供体 N-杂环卡宾亚基，我们获得了一个稳健的同配络合物 [Co(L ^CNC ) ₂ ](PF ₆)，具有光活性激发态，具有大量 MLCT 特征。与绝大多数等电子铁 (II) 配合物相比，[Co(L ^CNC ) ₂ ](PF ₆ ) 的 MLCT 态寿命较长，因为它不会有效地钝化为低位金属中心激发态；此外，它直接参与光致电子转移反应。与 [Fe(L ^CNC ) ₂ ](PF ₆ ) 的比较，以及结构、电化学和 UV-vis 瞬态吸收研究，提供了对具有光物理和光化学的第一行过渡金属配合物的新配体设计原则的见解与铂族金属相似的特性。

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Cobalt(III) Carbene Complex with an Electronic Excited-State Structure Similar to Cyclometalated Iridium(III) Compounds

Many organometallic iridium(III) complexes have photoactive excited states with mixed metal-to-ligand and intraligand charge transfer (MLCT/ILCT) character, which form the basis for numerous applications in photophysics and photochemistry. Cobalt(III) complexes with analogous MLCT excited-state properties seem to be unknown yet, despite the fact that iridium(III) and cobalt(III) can adopt identical low-spin d⁶ valence electron configurations due to their close chemical relationship. Using a rigid tridentate chelate ligand (L^CNC), in which a central amido π-donor is flanked by two σ-donating N-heterocyclic carbene subunits, we obtained a robust homoleptic complex [Co(L^CNC)₂](PF₆), featuring a photoactive excited state with substantial MLCT character. Compared to the vast majority of isoelectronic iron(II) complexes, the MLCT state of [Co(L^CNC)₂](PF₆) is long-lived because it does not deactivate as efficiently into lower-lying metal-centered excited states; furthermore, it engages directly in photoinduced electron transfer reactions. The comparison with [Fe(L^CNC)₂](PF₆), as well as structural, electrochemical, and UV–vis transient absorption studies, provides insight into new ligand design principles for first-row transition-metal complexes with photophysical and photochemical properties reminiscent of those known from the platinum group metals.

更新日期：2022-05-27

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