Tuning the Redox Potentials and Ligand Field Strength of Fe(II) Polypyridines: The Dual π-Donor and π-Acceptor Character of Bipyridine
Tuning the Redox Potentials and Ligand Field Strength of Fe(II) Polypyridines: The Dual π-Donor and π-Acceptor Character of Bipyridine
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DOI：
10.1021/acs.inorgchem.8b01002
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发表时间：
2018-08-20
影响因子：
4.6
通讯作者：
Jakubikova, Elena
中科院分区：
文献类型：
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作者：
Ashley, Daniel C.;Jakubikova, Elena
铁（II）多吡啶配合物中的五重态-单线态能量差（δ E-Q/S）通常用金属配体π相互作用来解释。对一系列取代的[Fe(bpy)(3)](2+) （bpy = 2,2'-联吡啶）配合物的DFT计算表明，取代基对调节δ E- q /S和还原电位（E度）的影响程度不同。在这个系列中，E的范围比Delta E- q /S大得多（2.07 vs 0.29 eV）。δ E- q /S的小变化是由金属配体Jr相互作用控制的，而E的大变化是由Fe中心周围静电环境的改变引起的。分子轨道分析表明，与bpy作为jr受体的典型描述相反，bpy在[Fe(bpy)(3)]（2+）配合物中作为pi给体和a受体被更好地描述，即使它被高吸电子取代基取代。总的来说，取代基修饰是一种微调配体场强的有用策略，但对于自旋态流形的显著重排序却不是，尽管它对金属-配体静电相互作用有很大影响。
The quintet-singlet energy difference (Delta E-Q/S) in Fe(II) polypyridine complexes is often interpreted in terms of metal ligand pi interactions. DFT calculations on a series of substituted [Fe(bpy)(3)](2+) (bpy = 2,2'-bipyridine) complexes show the disparate magnitudes of substituent effects on tuning Delta E-Q/S and reduction potentials (E degrees). In this series, E spans a much larger range than Delta E-Q/S (2.07 vs 0.29 eV). 'While small changes in Delta E-Q/S are controlled by metal ligand Jr interactions, large changes in E arise from modification of the electrostatic environment around the Fe center. Molecular orbital analysis reveals that, contrary to the typical description of bpy as a Jr-acceptor, bpy is better described as acting as both a pi-donor and a-acceptor in [Fe(bpy)(3)](2+) complexes, even when it is substituted with highly electron withdrawing substituents. Overall, substituent modification is a useful strategy for fine-tuning the ligand field strength but not for significant reordering of the spin-state manifold, despite the large effect on metal-ligand electrostatic interactions.