Experimental and Computational Study of the Structural and Electronic Properties of FeII(2,2′-bipyridine)(mes)2 and [FeII(2,2′-bipyridine)(mes)2]-, a Complex Containing a 2,2′-Bipyridyl Radical Anion
Experimental and Computational Study of the Structural and Electronic Properties of FeII(2,2′-bipyridine)(mes)2 and [FeII(2,2′-bipyridine)(mes)2]-, a Complex Containing a 2,2′-Bipyridyl Radical Anion
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DOI：
10.1021/ic100817s
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发表时间：
2010-07-05
影响因子：
4.6
通讯作者：
Goicoechea, Jose M.
中科院分区：
文献类型：
--
作者：
Irwin, Mark;Jenkins, Rhiannon K.;Goicoechea, Jose M.
在四氢呋喃（THF） Fe（2,2'-联吡啶）（mes）(2) （1; mes = 2,4,6- me3c6h2）溶液中加入金属钾和2,2,2-隐窝（4,7,13,16,21,24-己氧-1,10-重氮杂环[8.8.8]己基烷），得到阴离子络合物[Fe（2,2'-联吡啶）（mes）(2)](-)，分离为[K（2,2,2-隐窝）][Fe（2,2,2 '-联吡啶）（mes）(2)](2)和副产物[K（2,2,2-隐窝）][Fe(mes)(3)]中心点C6H12(3)。通过将2和3的混合物溶解在干吡啶中并将所得溶液与甲苯分层，获得了2的组成纯样品。1号材料的固态磁化率测量结果显示，在20 ~ 300 K范围内，其摩尔磁矩为5.12(1)mu(B)，具有居里-魏斯顺磁性；在2上进行的磁测量表明，铁（II）离子（S-Fe = 2）的未配对电子与联吡啶自由基（S-bipy = 1/2）的π *轨道之间存在更复杂的温度依赖行为，这与分子内反铁磁耦合（J=-46 cm(-1)）相一致。结构数据、穆斯堡尔和电子顺磁共振（EPR）光谱测量以及密度泛函理论（DFT）计算都与该电子结构模型一致。据我们所知，物种2代表了第一个具有晶体学特征的2,2'-联吡啶配体的过渡金属配合物，其磁性，光谱和计算数据表明π *反键轨道中存在未配对电子。
Addition of potassium metal and 2,2,2-crypt (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) to a tetrahydrofuran (THF) solution of Fe(2,2'-bipyridine)(mes)(2) (1; mes = 2,4,6-Me3C6H2) yielded the anionic complex [Fe(2,2'-bipyridine)(mes)(2)](-) which was isolated as [K(2,2,2-crypt)][Fe(2,2'-bipyridine)(mes)(2)] (2) alongside the side-product [K(2,2,2-crypt)][Fe(mes)(3)] center dot C6H12 (3). A compositionally pure sample of 2 was obtained by dissolving a mixture of 2 and 3 in dry pyridine and layering the resulting solution with toluene. Solid state magnetic susceptibility measurements on 1 reveal Curie-Weiss paramagnetic behavior with a molar magnetic moment of 5.12(1) mu(B) between 20 and 300 K, a value which is in line with the expected iron(II) spin-only value of 4.90 mu B. The magnetic measurements carried out on 2 reveal more complex temperature dependent behavior consistent with intramolecular antiferromagnetic coupling (J=-46 cm(-1)) between the unpaired electrons of the iron(II) ion (S-Fe = 2) and a pi* orbital of the bipyridyl radical (S-bipy = 1/2). Structural data, Mossbauer and electron paramagnetic resonance (EPR) spectroscopic measurements, and density functional theory (DFT) calculations are all consistent with this model of the electronic structure. To the best of our knowledge, species 2 represents the first crystallographically characterized transition metal complex of the 2,2'-bipyridyl ligand for which magnetic, spectroscopic, and computational data indicate the presence of an unpaired electron in the pi* antibonding orbital.