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Thermochromism of CuI tetrakisguanidine complexes: reversible activation of metal-to-ligand charge-transfer bands

Abstract Tetranuclear, intensely blue-coloured CuI complexes were synthesised in which two Cu2X3? units (X=Br or I) are bridged by a dicationic GFA (guanidino-functionalised aromatic) ligand. The UV/Vis spectra show a large metal-to-ligand charge-transfer (MLCT) band around 638?nm. The tetranuclear...

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Bibliographic Details
Main Authors: Wiesner, Sven (Author) , Wagner, Arne (Author) , Hübner, Olaf (Author) , Kaifer, Elisabeth (Author) , Himmel, Hans-Jörg (Author)
Format: Article (Journal)
Language:English
Published: September 29, 2015
In: Chemistry - a European journal
Year: 2015, Volume: 21, Issue: 46, Pages: 16494-16503
ISSN:1521-3765
DOI:10.1002/chem.201502584
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1002/chem.201502584
Verlag, lizenzpflichtig, Volltext: https://chemistry-europe.onlinelibrary.wiley.com/doi/full/10.1002/chem.201502584
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Author Notes:Sven Wiesner, Arne Wagner, Olaf Hübner, Elisabeth Kaifer, and Hans-Jörg Himmel
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Summary:Abstract Tetranuclear, intensely blue-coloured CuI complexes were synthesised in which two Cu2X3? units (X=Br or I) are bridged by a dicationic GFA (guanidino-functionalised aromatic) ligand. The UV/Vis spectra show a large metal-to-ligand charge-transfer (MLCT) band around 638?nm. The tetranuclear ?low-temperature? complexes are in a temperature-dependent equilibrium with dinuclear CuI ?high-temperature? complexes, which result from the reversible elimination of two CuX groups. A massive thermochromism effect results from the extinction of the strong MLCT band upon CuX elimination with increasing temperature. For all complexes, quantum chemical calculations predict a small and method-dependent energy difference between the possible electronic structures, namely CuI and dicationic GFA ligand (closed-shell singlet) versus CuII and neutral GFA ligand (triplet or broken-symmetry state). The closed-shell singlet state is disfavoured by hybrid-DFT functionals, which mix in exact Hartree?Fock exchange, and is favoured by larger basis sets and consideration of a polar medium.
Item Description:Gesehen am 01.07.2020
Im Titel ist "I" in CuI hochgestellt
Physical Description:Online Resource
ISSN:1521-3765
DOI:10.1002/chem.201502584

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