Ground-State Copper(III) Stabilized by N‑Confused/N-Linked Corroles: Synthesis, Characterization, and Redox Reactivity

Stable
square planar organocopper­(III) complexes (CuNCC2, CuNCC4, and CuBN) supported by carbacorrole-based
tetradentate macrocyclic ligands with NNNC coordination cores were
synthesized, and their structures were elucidated by spectroscopic
means including X-ray crystallographic analysis. On the basis of their
distinct planar structures, X-ray absorption/photoelectron spectroscopic
features, and temperature-independent diamagnetic nature, these organocopper
complexes can be preferably considered as novel organocopper­(III)
species. The remarkable stability of the high-valent Cu­(III) states
of the complexes stems from the closed-shell electronic structure
derived from the peculiar NNNC coordination of the corrole-modified
frameworks, which contrasts with the redox-noninnocent radical nature
of regular corrole copper­(II) complexes with an NNNN core. The proposed
structure was supported by DFT (B3LYP) calculations. Furthermore,
a π-laminated dimer architecture linked through the inner carbons
was obtained from the one-electron oxidation of CuNCC4. We envisage that the precise manipulation of the molecular orbital
energies and redox profiles of these organometallic corrole complexes
could eventually lead to the isolation of yet unexplored high-valent
metal species and the development of their organometallic reactions.

以碳卟啉（carbacorrole）基四齿大环配体（配位核为NNNC）负载的稳定方形平面有机铜(III)配合物（CuNCC2、CuNCC4及CuBN）经合成得到，其结构通过包括X射线晶体衍射分析在内的光谱表征手段得以解析。基于其独特的平面结构、X射线吸收/光电子光谱特征以及与温度无关的抗磁性，这类有机铜配合物可被认定为新型有机铜(III)物种。该类配合物高价铜(III)价态的优异稳定性，源自卟啉改性骨架特殊的NNNC配位模式所赋予的闭壳层电子结构，这与具有NNNN配位核的常规卟啉铜(II)配合物的氧化还原非innocent自由基特性形成鲜明对比。所提出的配合物结构得到了密度泛函理论（Density Functional Theory, DFT，B3LYP泛函）计算的佐证。此外，通过对CuNCC4进行单电子氧化，可获得由内部碳原子连接的π堆叠二聚体结构。我们认为，精准调控这类有机金属卟啉配合物的分子轨道能级与氧化还原特性，有望最终分离得到尚未被探索的高价金属物种，并推动其有机金属反应的发展。