Synthesis, structure, and physical properties for a series of monomeric iron(III) hydroxo complexes with varying hydrogen-bond networks
Synthesis, structure, and physical properties for a series of monomeric iron(III) hydroxo complexes with varying hydrogen-bond networks
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DOI：
10.1021/ic800048e
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发表时间：
2008-07-07
影响因子：
4.6
通讯作者：
Borovik, A. S.
中科院分区：
文献类型：
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作者：
Mukherjee, Jhumpa;Lucas, Roble L.;Borovik, A. S.
具有末端羟基配体的单核铁(III)络合物被认为是几种金属蛋白中的重要物种，但它们在合成体系中一直难以分离。利用一系列酰胺/脲三脚架配体，我们合成并表征了具有相似的三角-双锥体初级配位球的单体(FeOH)-O-III配合物。三个阴离子氮给体定义了三角平面，羟基氧原子被转化为顶端的胺氮原子。配合物具有不同的二次配位球，这些二次配位球由(FeOH)-O-III单元和尿素NH基团之间的分子内氢键定义。氢键数目与Fe-O-羟基键距离之间存在结构趋势：分子内氢键越多，Fe-O键越长。光谱趋势也被发现，包括O-H振动的能量增加，氢键的数目减少。然而，Fe-III/II还原电位在整个系列中是恒定的(类似于2.0V vs[Cp2Fe](0/+1))，这归因于初级和次级配位球效应的平衡。
Mononuclear iron(III) complexes with terminal hydroxo ligands are proposed to be important species in several metalloproteins, but they have been difficult to isolate in synthetic systems. Using a series of amidate/ureido tripodal ligands, we have prepared and characterized monomeric (FeOH)-O-III complexes with similar trigonal-bipyramidal primary coordination spheres. Three anionic nitrogen donors define the trigonal plane, and the hydroxo oxygen atom is trans to an apical amine nitrogen atom. The complexes have varied secondary coordination spheres that are defined by intramolecular hydrogen bonds between the (FeOH)-O-III unit and the urea NH groups. Structural trends were observed between the number of hydrogen bonds and the Fe-O-hydroxo bond distances: the more intramolecular hydrogen bonds there were, the longer the Fe-O bond became. Spectroscopic trends were also found, including an increase in the energy of the O-H vibrations with a decrease in the number of hydrogen bonds. However, the Fe-III/II reduction potentials were constant throughout the series (similar to 2.0 V vs [Cp2Fe](0/+1)), which is ascribed to a balancing of the primary and secondary coordination-sphere effects.