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One- versus two-electron oxidation of complexed guanidino-functionalized aromatic compounds

Herein, we report a rational synthetic access to dinuclear CuII complexes with radical monocationic guanidine ligands. The starting point was the first directed synthesis of a dinuclear CuII complex of the redox-active, neutral guanidino-functionalized aromatic (GFA) compound 1,2,4,5-tetrakis(tetram...

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Main Authors: Trumm, Christine Helga (Author) , Hübner, Olaf (Author) , Walter, Petra (Author) , Leingang, Simone (Author) , Wild, Ute (Author) , Kaifer, Elisabeth (Author) , Eberle, Benjamin (Author) , Himmel, Hans-Jörg (Author)
Format: Article (Journal)
Language:English
Published: 06 November 2014
In: European journal of inorganic chemistry
Year: 2014, Issue: 35, Pages: 6039-6050
ISSN:1099-0682
DOI:10.1002/ejic.201402840
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1002/ejic.201402840
Verlag, lizenzpflichtig, Volltext: https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/ejic.201402840
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Author Notes:Christine Trumm, Olaf Hübner, Petra Walter, Simone Leingang, Ute Wild, Elisabeth Kaifer, Benjamin Eberle, and Hans-Jörg Himmel
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Summary:Herein, we report a rational synthetic access to dinuclear CuII complexes with radical monocationic guanidine ligands. The starting point was the first directed synthesis of a dinuclear CuII complex of the redox-active, neutral guanidino-functionalized aromatic (GFA) compound 1,2,4,5-tetrakis(tetramethylguanidino)benzene (1) as ligand by treatment of 1 with Cu(OAc)2. The neutral complex [1Cu(OAc)22] was then oxidized with several oxidizing reagents. With I2 two-electron oxidation occurred, thus leading to green salts of the dication [1Cu(OAc)22]2+. In contrast, with AgPF6 or AgSbF6 one-electron oxidation was observed to yield red salts of the monocation [1Cu(OAc)22]+, which is a three-spin system with one unpaired electron at each copper atom and at the ligand unit. Superconducting quantum interference device (SQUID) magnetometric measurements confirm a quartet electronic ground state that arises from strong ferromagnetic copper-ligand coupling. Intense charge-transfer transitions in the visible region (576 and 536 nm) were observed in the electronic absorption spectra and assigned to strong ligand-ligand (1·+←OAc) charge-transfer (LLCT) excitations. These LLCT bands open up the possibility of photoinduced redox reactions with [1Cu(OAc)22]+ driven by restoration of the aromatic system at the GFA ligand.
Item Description:Gesehen am 06.11.2020
Physical Description:Online Resource
ISSN:1099-0682
DOI:10.1002/ejic.201402840

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