Equipe de Chimie Inorganique Redox Biomimétique, Département de Chimie Moléculaire, Université Joseph Fourier, 38041 Grenoble Cedex 9, France.
Inorg Chem. 2012 Oct 15;51(20):10557-71. doi: 10.1021/ic300763t. Epub 2012 Sep 26.
Square planar cobalt(II) complexes of salen ligands N,N'-bis(3-tert-butyl-5R-salicylidene)-1,2-cyclohexanediamine), where R = OMe (1) and tert-butyl (2), were prepared. 1 and 2 were electrochemically reversibly oxidized into cations 1-H(2)O and 2-H(2)O in CH(2)Cl(2). The chemically generated 1-H(2)O·0.68 H(2)O·0.82CH(2)Cl(2) and 2-H(2)O·0.3H(2)O·0.85CH(2)Cl(2) were characterized by X-ray diffraction and NIR spectroscopy. Both complexes are paramagnetic species containing a square pyramidal cobalt ion coordinated at the apical position by an exogenous water molecule. They exhibit remarkable NIR bands at 1220 (7370 M(-1) cm(-1)) and 1060 nm (5560 M(-1) cm(-1)), respectively, assigned to a CT transition. DFT calculations and magnetic measurements confirm the paramagnetic (S = 1) ground spin state of the cations. They show that more than 70% of the total spin density in 1-H(2)O and 2-H(2)O is localized on the metal, the remaining spin density being distributed over the aromatic rings (30% phenoxyl character). In the presence of N-methylimidazole 1 and 2 are irreversibly oxidized by air into the genuine octahedral cobalt(III) bis(phenolate) complexes 1-im(2) and 2-im(2), the former being structurally characterized. Neither 1-im(2) nor 2-im(2) exhibits a NIR feature in its electronic spectrum. 1 and 2 were electrochemically two-electron oxidized into 1 and 2. The cations were identified as Co(III)-phenoxyl species by their characteristic absorption band at ca. 400 nm in the UV-vis spectrum. Coordination of the phenoxyl radical to the cobalt(III) metal ion is evidenced by the EPR signal centered at g = 2.00.
席夫碱配体 N,N'-双(3-叔丁基-5R-水杨醛基)-1,2-环己二胺)的正方形平面钴(II)配合物，其中 R = OMe (1) 和叔丁基 (2)，被制备。1 和 2 在 CH(2)Cl(2)中电化学可逆地氧化为阳离子 1-H(2)O 和 2-H(2)O。通过 X 射线衍射和近红外光谱对化学生成的 1-H(2)O·0.68 H(2)O·0.82CH(2)Cl(2) 和 2-H(2)O·0.3H(2)O·0.85CH(2)Cl(2)进行了表征。这两个配合物都是含有一个在顶点位置由外源水分子配位的正方形金字塔钴离子的顺磁性物种。它们在 1220（7370 M(-1) cm(-1)) 和 1060 nm（5560 M(-1) cm(-1)) 处分别显示出显著的近红外带，分别归因于 CT 跃迁。DFT 计算和磁性测量证实了阳离子的顺磁（S = 1）基自旋态。它们表明，1-H(2)O 和 2-H(2)O 中的总自旋密度超过 70%定域在金属上，剩余的自旋密度分布在芳环上（30% 苯氧基特征）。在 N-甲基咪唑存在下，1 和 2 被空气不可逆地氧化为真正的八面体钴(III)双(苯氧)配合物 1-im(2) 和 2-im(2)，前者的结构得到了表征。1-im(2) 和 2-im(2) 都没有在其电子光谱中显示出近红外特征。1 和 2 通过电化学两电子氧化为 1 和 2。通过在紫外可见光谱中约 400 nm 处的特征吸收带，将阳离子鉴定为 Co(III)-苯氧自由基物种。苯氧自由基与钴(III)金属离子的配位由 g = 2.00 处的 EPR 信号证实。
