Enabling Valence Delocalization in Iron(III) Macrocyclic Complexes through Ring Unsaturation.
Enabling Valence Delocalization in Iron(III) Macrocyclic Complexes through Ring Unsaturation.
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DOI：
10.1021/acs.inorgchem.3c01179
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发表时间：
2023-06
影响因子：
4.6
通讯作者：
Reese A. Clendening;Stephanie S Delancey;Andrew T Poore;Shan Xue;Yisong Guo;Shiliang Tian;T. Ren
中科院分区：
文献类型：
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作者：
Reese A. Clendening;Stephanie S Delancey;Andrew T Poore;Shan Xue;Yisong Guo;Shiliang Tian;T. Ren
合成了配合物[FeIII(HMC)(C2DMA)2]CF3SO3([2]OTf)和[FeIII(HMTi)(C2Y)2]CF3SO3([3a-c]OTf)，并对其进行了结构表征(Hmc=5，5，7，12，12，14-hexamethyl-1，4，8，11-tetraazacyclotetradecane；HMTi=5，5，7，12，12，14-hexamethyl-1，4，8，11-tetraazacyclotetradeca-1，3，8，10-tetraene；Y=FC(二茂铁基，[3a]OTf)、4-(N，N-二甲基)苯胺基(DMA，[3b]OTf)或4-(N，N-二(4-甲氧基苯基)苯胺基(TPA，[3c]OTf)；OTf-=CF3SO3-)。乙炔取代基Y的单电子氧化后的振动和电子吸收光谱电化学分析表明，所有基于HMTi的化合物在生成的混合价物种中都有强烈的偶合。然而，基于[2]OTF的类似的混合价离子似乎更具局域性。因此，四亚胺大环HMTi使得-C2-FeIII-C2-桥上的价离域化显著。[3b]OTf的电子顺磁共振和穆斯堡尔谱研究表明，与纯π供体的HMC相比，HMTi的π-酸性降低了Fe3 dσ轨道的能量。这一观察结果为解释大周期依赖的价(De)局域化提供了基础。
The complexes [FeIII(HMC)(C2DMA)2]CF3SO3 ([2]OTf) and [FeIII(HMTI)(C2Y)2]CF3SO3 ([3a-c]OTf) have been prepared and thoroughly characterized (HMC = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; HMTI = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene; Y = Fc (ferrocenyl, [3a]OTf), 4-(N,N-dimethyl)anilino (DMA, [3b]OTf), or 4-(N,N-bis(4-methoxyphenyl)anilino (TPA, [3c]OTf); OTf- = CF3SO3-)). Vibrational and electronic absorption spectroelectrochemical analyses following one-electron oxidation of the ethynyl substituent Y revealed evidence of strong coupling in the resultant mixed valent species for all HMTI-based complexes. However, the analogous mixed valent ion based on [2]OTf appeared to be more localized. Thus, the tetra-imino macrocycle HMTI has enabled significant valence delocalization along the -C2-FeIII-C2- bridge. Electron paramagnetic resonance and Mössbauer spectroscopic studies of [3b]OTf reveal that the π-acidity of HMTI lowers the energy of the FeIII dπ orbitals compared to the purely σ-donating HMC. This observation provides a basis for the interpretation of the macrocycle-dependent valence (de)localization.