Mukherjee Chandan, Pieper Ulrich, Bothe Eberhard, Bachler Vinzenz, Bill Eckhard, Weyhermüller Thomas, Chaudhuri Phalguni
Max-Planck-Institute for Bioinorganic Chemistry, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
Inorg Chem. 2008 Oct 6;47(19):8943-56. doi: 10.1021/ic8009767. Epub 2008 Aug 28.
Seven new bis(o-iminosemiquinonato)copper(II) complexes, 1- 5, 1a, 1b, derived from differently substituted N-phenyl-2-aminophenol-based ligands, are described. Their crystal structures were determined by X-ray diffraction, and their electronic structures were established by various physical methods including electron paramagnetic resonance and variable-temperature (2-290 K) susceptibility measurements. Like complex 6, which was reported recently by us, all complexes exhibit an S t = (1)/ 2 ground state, based on the "isolated" copper(II)-spin character resulting from the dominating antiferromagnetic spin coupling between the two radicals; the ground-state electronic configuration can thus be designated as (increasing, increasing, decreasing)[R-Cu-R]. In addition, broken spin symmetry density functional solutions have been obtained. From the set of unrestricted canonical Kohn-Sham orbitals, the magnetic orbitals have been identified. The identification procedure is based on the nonvanishing overlap integrals between the space parts of orbitals occupied by electrons of opposite spin. The theoretically determined magnetic orbitals support the spin configurations suggested by the experiments. Electrochemical measurements (cyclic voltammetry and square-wave voltammetry) indicate ligand-centered redox processes. Complex 1 is found to be the best catalyst among the Cu(II) complexes for oxidation of primary alcohols with aerial oxygen as the sole oxidant to afford aldehydes under mild conditions. Thus, the function of the copper-containing enzyme Galactose Oxidase has been mimicked. Kinetic measurements in conjunction with electron paramagnetic resonance and electronic spectral studies have been used to decipher the catalytic oxidation process. A ligand-derived redox activity has been proposed as a mechanism for the aerial oxidation of primary alcohols.
本文描述了七种新型双（邻亚胺基半醌）铜（II）配合物，即1 - 5、1a、1b，它们由不同取代的N - 苯基 - 2 - 氨基酚基配体衍生而来。通过X射线衍射确定了它们的晶体结构，并通过包括电子顺磁共振和变温（2 - 290 K）磁化率测量在内的各种物理方法确定了它们的电子结构。与我们最近报道的配合物6一样，基于两个自由基之间占主导的反铁磁自旋耦合产生的“孤立”铜（II）自旋特征，所有配合物都表现出(S_t = \frac{1}{2})基态；因此，基态电子构型可指定为（增加，增加，减少）[R - Cu - R]。此外，还获得了破缺自旋对称性密度泛函解。从无限制规范的Kohn - Sham轨道集合中，识别出了磁性轨道。识别过程基于相反自旋电子占据的轨道空间部分之间非零的重叠积分。理论确定的磁性轨道支持了实验所暗示的自旋构型。电化学测量（循环伏安法和方波伏安法）表明存在以配体为中心的氧化还原过程。发现配合物1是铜（II）配合物中用于以空气中的氧气作为唯一氧化剂将伯醇氧化为醛的最佳催化剂，反应在温和条件下进行。因此，模拟了含铜酶半乳糖氧化酶的功能。结合电子顺磁共振和电子光谱研究的动力学测量已被用于解读催化氧化过程。已提出配体衍生的氧化还原活性作为伯醇空气氧化的一种机制。
