朝向功能化的羧酸桥联双核铁蛋白模拟物：使用大环配体框架实现结构稳定性和构象灵活性。
Toward functional carboxylate-bridged diiron protein mimics: achieving structural stability and conformational flexibility using a macrocylic ligand framework.
机构信息
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
出版信息
J Am Chem Soc. 2011 Jul 13;133(27):10568-81. doi: 10.1021/ja2021312. Epub 2011 Jun 17.
A dinucleating macrocycle, H(2)PIM, containing phenoxylimine metal-binding units has been prepared. Reaction of H(2)PIM with [Fe(2)(Mes)(4)] (Mes = 2,4,6-trimethylphenyl) and sterically hindered carboxylic acids, Ph(3)CCO(2)H or Ar(Tol)CO(2)H (2,6-bis(p-tolyl)benzoic acid), afforded complexes [Fe(2)(PIM)(Ph(3)CCO(2))(2)] (1) and [Fe(2)(PIM)(Ar(Tol)CO(2))(2)] (2), respectively. X-ray diffraction studies revealed that these diiron(II) complexes closely mimic the active site structures of the hydroxylase components of bacterial multicomponent monooxygenases (BMMs), particularly the syn disposition of the nitrogen donor atoms and the bridging μ-η(1)η(2) and μ-η(1)η(1) modes of the carboxylate ligands at the diiron(II) centers. Cyclic voltammograms of 1 and 2 displayed quasi-reversible redox couples at +16 and +108 mV vs ferrocene/ferrocenium, respectively. Treatment of 2 with silver perchlorate afforded a silver(I)/iron(III) heterodimetallic complex, [Fe(2)(μ-OH)(2)(ClO(4))(2)(PIM)(Ar(Tol)CO(2))Ag] (3), which was structurally and spectroscopically characterized. Complexes 1 and 2 both react rapidly with dioxygen. Oxygenation of 1 afforded a (μ-hydroxo)diiron(III) complex [Fe(2)(μ-OH)(PIM)(Ph(3)CCO(2))(3)] (4), a hexa(μ-hydroxo)tetrairon(III) complex [Fe(4)(μ-OH)(6)(PIM)(2)(Ph(3)CCO(2))(2)] (5), and an unidentified iron(III) species. Oxygenation of 2 exclusively formed di(carboxylato)diiron(III) compounds, a testimony to the role of the macrocylic ligand in preserving the dinuclear iron center under oxidizing conditions. X-ray crystallographic and (57)Fe Mössbauer spectroscopic investigations indicated that 2 reacts with dioxygen to give a mixture of (μ-oxo)diiron(III) [Fe(2)(μ-O)(PIM)(Ar(Tol)CO(2))(2)] (6) and di(μ-hydroxo)diiron(III) [Fe(2)(μ-OH)(2)(PIM)(Ar(Tol)CO(2))(2)] (7) units in the same crystal lattice. Compounds 6 and 7 spontaneously convert to a tetrairon(III) complex, [Fe(4)(μ-OH)(6)(PIM)(2)(Ar(Tol)CO(2))(2)] (8), when treated with excess H(2)O.
一种双氮大环化合物 H(2)PIM，其中包含苯并恶嗪金属结合单元，已经被制备出来。H(2)PIM 与 [Fe(2)(Mes)(4)]（Mes = 2,4,6-三甲基苯基）和空间位阻羧酸 Ph(3)CCO(2)H 或 Ar(Tol)CO(2)H（2,6-双（对甲苯基）苯甲酸）反应，分别得到了配合物 [Fe(2)(PIM)(Ph(3)CCO(2))(2)]（1）和 [Fe(2)(PIM)(Ar(Tol)CO(2))(2)]（2）。X 射线衍射研究表明，这些二铁(II)配合物紧密模拟了细菌多组分单加氧酶（BMM）中羟化酶成分的活性部位结构，特别是氮供体原子的顺式排列以及羧酸盐配体在二铁(II)中心的桥联 μ-η(1)η(2)和 μ-η(1)η(1)模式。1 和 2 的循环伏安图在+16 和+108 mV 相对于铁电/铁电对分别显示出准可逆氧化还原对。2 与高氯酸银反应得到了银(I)/铁(III)杂二金属配合物 [Fe(2)(μ-OH)(2)(ClO(4))(2)(PIM)(Ar(Tol)CO(2))Ag]（3），其结构和光谱特征已得到证实。配合物 1 和 2 均能快速与氧气反应。1 的氧合作用生成了（μ-羟基金属）二铁(III)配合物 [Fe(2)(μ-OH)(PIM)(Ph(3)CCO(2))(3)]（4）、六（μ-羟基金属）四铁(III)配合物 [Fe(4)(μ-OH)(6)(PIM)(2)(Ph(3)CCO(2))(2)]（5）和一种未鉴定的铁(III)物种。2 的氧合作用仅形成二（羧酸盐）二铁(III)化合物，这证明了大环配体在氧化条件下保持双核铁中心的作用。X 射线晶体学和 (57)Fe Mössbauer 光谱研究表明，2 与氧气反应生成（μ-氧基金属）二铁(III) [Fe(2)(μ-O)(PIM)(Ar(Tol)CO(2))(2)]（6）和二（μ-羟基金属）二铁(III) [Fe(2)(μ-OH)(2)(PIM)(Ar(Tol)CO(2))(2)]（7）在同一晶体晶格中的混合物。当用过量的 H(2)O 处理时，化合物 6 和 7 会自发转化为四铁(III)配合物 [Fe(4)(μ-OH)(6)(PIM)(2)(Ar(Tol)CO(2))(2)]（8）。
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