Department of Physics, University of Antwerp, B-2610 Antwerp, Belgium.
Inorg Chem. 2010 Mar 1;49(5):2083-92. doi: 10.1021/ic901849e.
The activation of N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamino Co(II), [Co(II)(1)], by the addition of acetic acid under aerobic conditions has been investigated by a range of spectroscopic techniques including continuous-wave EPR, HYSCORE, pulsed ENDOR, and resonance Raman. These measurements have revealed for the first time the formation of a coordinated cobalt(III)-bound phenoxyl radical labeled Co(III)(1(*))(OAc)(n)(m) (n = m = 1 or n = 2, m = 0). This cobalt(III)-bound phenoxyl radical is characterized by the following spin Hamiltonian parameters: g(x) = 2.0060, g(y) = 2.0031, g(z) = 1.9943, A(x) = 17 MHz, A(y) = 55 MHz, and A(z) = 14 MHz. Although the radical contains coordinated acetate(s), the experiments unambiguously proved that the phenoxyl radical is situated on ligand (1) as opposed to a phenoxyl radical ligated to cobalt in the axial position. Density functional theory computations on different models corroborate the stability of such a phenoxyl radical species and suggest the ligation of one or two acetate molecules to the complex. A mechanism is proposed, which accounts for the formation of this unusual and extremely robust phenoxyl radical, never previously observed for [Co(1)].
在有氧条件下，通过添加醋酸，研究了 N,N'-双(3,5-二叔丁基水杨醛)-1,2-环己二胺合钴(II)，[Co(II)(1)]的激活作用。这些测量首次揭示了形成配位钴(III)结合的酚氧基自由基标记的Co(III)(1(*))(OAc)(n)(m) (n = m = 1 或 n = 2, m = 0)。这种钴(III)结合的酚氧基自由基的自旋哈密顿参数如下：g(x) = 2.0060, g(y) = 2.0031, g(z) = 1.9943, A(x) = 17 MHz, A(y) = 55 MHz, 和 A(z) = 14 MHz。尽管自由基含有配位的醋酸根，但实验明确证明，酚氧基自由基位于配体(1)上，而不是位于轴向位置与钴配位的酚氧基自由基。不同模型的密度泛函理论计算证实了这种酚氧基自由基物种的稳定性，并表明一个或两个醋酸分子与配合物的配位。提出了一种机制，该机制解释了这种不寻常且极其稳定的酚氧基自由基的形成，这在以前的[Co(1)]中从未观察到过。
