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Diruthenium Complexes of p‐Benzoquinone–Imidazole Hybrid Ligands: Innocent or Noninnocent Behavior of the Quinone Moiety
Chemistry - An Asian Journal ( IF 3.5 ) Pub Date : 2018-09-11 , DOI: 10.1002/asia.201801101
Mohd. Asif Ansari 1 , Katharina Beyer 2 , Brigitte Schwederski 2 , Wolfgang Kaim 2 , Goutam Kumar Lahiri 1
Affiliation  

After double deprotonation, 2,6‐diaryl‐p‐benzoquinonodiimidazoles (aryl=4‐tolyl (I) or 2‐pyridyl (II)) were shown to bridge two [Ru(bpy)2]2+ (bpy=2,2‐bipyridine) complex fragments through the imidazolate N and p‐quinone O (I12+) or through the imidazolate N and pyridyl N donor atoms (II22+). Characterization by crystal structure analysis, 1H/13C NMR spectroscopy, cyclic and differential pulse voltammetry, and spectroelectrochemistry (UV/Vis/NIR, IR, EPR) in combination with TD‐DFT calculations revealed surprisingly different electronic structures for redox systems 1n and 2n. Whereas 12+ is reduced to a radical complex with considerable semiquinone character, the reduction of 22+ with its exclusive N coordination exhibits little spin on the now redox‐innocent quinone moiety, compared with the electron uptake by the pyridyl–imidazolate chelating site. The first of two close‐lying oxidation processes occurs at the bridging heteroquinone ligand, whereas the second oxidation is partly (14+) or predominantly (24+) centered on the metal atoms.

中文翻译:

对苯醌-咪唑杂配体的钌络合物:醌部分的无害或无害行为

双重去质子化后,显示2,6-二芳基-对-苯并醌二咪唑(芳基= 4-甲苯基(I)或2-吡啶基(II))桥接两个[Ru(bpy)2 ] 2+(bpy = 2,2 ′-联吡啶)的复合物通过咪唑化物N和对苯醌O(I1 2+)或通过咪唑化物N和吡啶基N供体原子(II2 2+)裂解。通过晶体结构分析表征,1 H / 13C NMR光谱法,循环和差分脉冲伏安法以及光谱电化学法(UV / Vis / NIR,IR,EPR)与TD-DFT计算相结合,揭示了氧化还原系统1 n2 n令人惊讶的不同电子结构。尽管1 2+被还原为具有相当半醌特征的自由基配合物,但2 2+的独特N配位还原却使现在的氧化还原-无辜醌部分几乎没有自旋,而吡啶基-咪唑化物螯合位点则吸收了电子。 。两个紧密的氧化过程中的第一个发生在桥接的杂醌配体上,而第二个氧化过程的一部分(1 4+)或主要(2 4+)以金属原子为中心。
更新日期:2018-09-11
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