Steric restraints in redox-active guanidine ligands and their impact on coordination chemistry
The introduction of redox-active ligands into coordination compounds is attractive for a number of applications; intramolecular electron transfer between a redox-active ligand and a metal is the basis for applications in switchable devices and advanced redox catalysis for multielectron substrate act...
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| Main Authors: | , , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
November 25, 2025
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| In: |
Chemistry - a European journal
Year: 2025, Volume: 31, Issue: 66, Pages: 1-13 |
| ISSN: | 1521-3765 |
| DOI: | 10.1002/chem.202502457 |
| Online Access: | Verlag, kostenfrei, Volltext: https://doi.org/10.1002/chem.202502457 Verlag, kostenfrei, Volltext: https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.202502457 
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| Author Notes: | Eliane Engels, Hanna Koepcke, Marko Lörsch, Patrick David Römgens, Anna Katharina Helm, Simone Leingang, Elisabeth Kaifer, and Hans-Jörg Himmel |
| Summary: | The introduction of redox-active ligands into coordination compounds is attractive for a number of applications; intramolecular electron transfer between a redox-active ligand and a metal is the basis for applications in switchable devices and advanced redox catalysis for multielectron substrate activations. A fine-tuning of the properties of redox-active ligands focusses on the redox potential and frontier orbital energies, as well as the steric demand and coordination mode. In this work, we report the first synthesis of new o-diguanidino-benzene ligands in which the two guanidino groups are connected through an alkyl chain of different length. The introduction of an ethylene bridge between the two guanidino groups turns a strongly coordinating ligand into a noncoordinating molecule, while keeping its strong Brønsted basicity. These features qualify the ethylene-bridged compound as a powerful alternative to Huenig's base, diisopropyl-ethyl-amine. The change from an ethylene to a propylene bridge switches back on the coordination ability. It is also possible to introduce a methyl group to the central C atom of the propylene bridge without loss of nucleophilic properties. The analysis, based on a variety of metal complexes, identifies three structural parameters to assay the structural restraint. Macrocyclic tetraguanidines are also formed. |
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| Item Description: | Zuerst veröffentlicht: 25. Oktober 2025 Gesehen am 02.12.2025 |
| Physical Description: | Online Resource |
| ISSN: | 1521-3765 |
| DOI: | 10.1002/chem.202502457 |