Switching from metal- to ligand-based oxidation in cobalt complexes with redox-active bisguanidine ligands
The control of the redox reactivity, magnetic and optical properties of the different redox states of complexes with redox-active ligands permits their rational use in catalysis and materials science. The redox-chemistry of octahedrally coordinated high-spin CoII complexes (three unpaired electrons)...
Saved in:
| Main Authors: | , , , |
|---|---|
| Format: | Article (Journal) |
| Language: | English |
| Published: |
2021
|
| In: |
Chemistry - a European journal
Year: 2021, Volume: 27, Issue: 46, Pages: 11852-11867 |
| ISSN: | 1521-3765 |
| DOI: | 10.1002/chem.202101364 |
| Online Access: | Verlag, kostenfrei, Volltext: https://doi.org/10.1002/chem.202101364 Verlag, kostenfrei, Volltext: https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.202101364 
|
| Author Notes: | Lukas Lohmeyer, Elisabeth Kaifer, Markus Enders, and Hans-Jörg Himmel |
| Summary: | The control of the redox reactivity, magnetic and optical properties of the different redox states of complexes with redox-active ligands permits their rational use in catalysis and materials science. The redox-chemistry of octahedrally coordinated high-spin CoII complexes (three unpaired electrons) with one redox-active bisguanidine ligand and two acetylacetonato (acac) co-ligands is completely changed by replacing the acac by hexafluoro-acetylacetonato (hfacac) co-ligands. The first one-electron oxidation is metal-centered in the case of the complexes with acac co-ligands, giving diamagnetic CoIII complexes. By contrast, in the case of the less Lewis-basic hfacac co-ligands, the first one-electron oxidation becomes ligand-centered, leading to high-spin CoII complexes with a radical monocationic guanidine ligand unit (four unpaired electrons). Ferromagnetic coupling between the spins on the metal and the organic radical in solution is evidenced by temperature-dependent paramagnetic NMR studies, allowing to estimate the isotropic exchange coupling constant in solution. Second one-electron oxidation leads to high-spin CoII complexes with dicationic guanidine ligand units (three unpaired electrons) in the presence of hfacac co-ligands, but to low-spin CoIII complexes with radical monocationic, peralkylated guanidine ligand (one unpaired electron) in the presence of acac co-ligands. The analysis of the electronic structures is complemented by quantum-chemical calculations on the spin density distributions and relative energies of the possible redox isomers. |
|---|---|
| Item Description: | First published: 08 June 2021 Gesehen am 25.11.2022 |
| Physical Description: | Online Resource |
| ISSN: | 1521-3765 |
| DOI: | 10.1002/chem.202101364 |