Synthesis and Electronic Structure Determination of N-Alkyl-Substituted Bis(imino)pyridine Iron Imides Exhibiting Spin Crossover Behavior
Synthesis and Electronic Structure Determination of N-Alkyl-Substituted Bis(imino)pyridine Iron Imides Exhibiting Spin Crossover Behavior
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DOI：
10.1021/ja205736m
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发表时间：
2011-11-02
影响因子：
15
通讯作者：
Chirik, Paul J.
中科院分区：
文献类型：
--
作者：
Bowman, Amanda C.;Milsmann, Carsten;Chirik, Paul J.
合成了三种新的N-烷基取代双（亚氨基）吡啶铁酰亚胺配合物（（PDI）-P-iPr）FeNR（（PDI）-P-iPr = 2，6-（2，6-Pr-i（2）-C6H3-N=CMe）（2）C5H3N; R = 1-金刚烷基（（1）Ad）、环辛基（（Cy）Oct）和2-金刚烷基（（2）Ad（二氮）配合物（（PDI）-P-iPr）Fe（N-2）（2）。对异构铁酰亚胺（（PDI）-P-iPr）FeN（1）Ad和（（PDI）-P-iPr）FeN（2）Ad）的SQUID磁性测量建立了自旋交叉行为，后一个示例在实验可达到的温度范围内具有更完整的自旋转变。所有三个烷基取代的双（亚氨基）吡啶铁酰亚胺的X射线衍射建立基本上平面的化合物与相对较短的Fe-Nd-酰亚胺键长和两个电子还原的氧化还原活性的双（亚氨基）吡啶螯合物。零场和应用场穆斯堡尔谱测量表明在低温下的抗磁性基态和建立低异构体位移符合高度共价分子。对于（（PDI）-P-iPr）FeN（2）Ad，穆斯堡尔谱也支持自旋交叉行为，并允许提取S = 0到S = 1跃迁的热力学参数。X射线吸收光谱和计算研究也进行了探索的电子结构的双（亚氨基）吡啶烷基取代的酰亚胺。低自旋铁中心（S = 1/2）反铁磁耦合到一个酰亚胺基自由基（S-酰亚胺= 1/2）和一个封闭的壳层，双阴离子双（亚氨基）吡啶螯合物（S-PDI = 0）的电子结构的描述是有利的S = 0状态。一个铁为中心的自旋过渡到一个中间自旋铁离子（S-Fe = 3/2）占在较高温度下观察到的S = 1状态。基于计算和实验数据的其他可能性也进行了评估和比较的电子结构的双（亚氨基）吡啶铁N-芳基酰亚胺对应物。
Three new N-alkyl substituted bis(imino)pyridine iron imide complexes, ((PDI)-P-iPr)FeNR ((PDI)-P-iPr = 2, 6-(2,6-Pr-i(2)-C6H3-N=CMe)(2)C5H3N; R = 1-adamantyl ((1)Ad), cyclooctyl ((Cy)Oct), and 2-adamantyl ((2)Ad)) were synthesized by addition of the appropriate alkyl azide to the iron bis(dinitrogen) complex, ((PDI)-P-iPr)Fe(N-2)(2). SQUID magnetic measurements on the isomeric iron imides, ((PDI)-P-iPr)FeN(1)Ad and ((PDI)-P-iPr)FeN(2)Ad, established spin crossover behavior with the latter example having a more complete spin transition in the experimentally accessible temperature range. X-ray diffraction on all three alkyl-substituted bis(imino)pyridine iron imides established essentially planar compounds with relatively short Fe-Nd-imide bond lengths and two-electron reduction of the redox-active bis(imino)pyridine chelate. Zero- and applied-field Mossbauer spectroscopic measurements indicate diamagnetic ground states at cryogenic temperatures and established low isomer shifts consistent with highly covalent molecules. For ((PDI)-P-iPr)FeN(2)Ad, Mossbauer spectroscopy also supports spin crossover behavior and allowed extraction of thermodynamic parameters for the S = 0 to S = 1 transition. X-ray absorption spectroscopy and computational studies were also performed to explore the electronic structure of the bis(imino)pyridine alkyl-substituted imides. An electronic structure description with a low spin ferric center (S = 1/2) antiferromagnetically coupled to an imidyl radical (S-imide = 1/2) and a closed-shell, dianionic bis(imino)pyridine chelate (S-PDI = 0) is favored for the S = 0 state. An iron-centered spin transition to an intermediate spin ferric ion (S-Fe = 3/2) accounts for the S = 1 state observed at higher temperatures. Other possibilities based on the computational and experimental data are also evaluated and compared to the electronic structure of the bis(imino)pyridine iron N-aryl imide counterparts.