Solvent Control of Ligand–Metal Electron Transfer in Mononuclear Copper Complexes with Redox‐Active Bisguanidine Ligands

• Published in: European journal of inorganic chemistry 2018-08, Vol.2018 (32), p.3660-3667
• Main Authors: Schrempp, David F., Kaifer, Elisabeth, Himmel, Hans‐Jörg
• Format: Article
• Language: English
• Subjects: Catalysis; Coordination chemistry; Coordination compounds; Copper; Copper compounds; Electron transfer; Electronic structure; Inorganic chemistry; Ligands; Organic chemistry; Polarity; Quantum chemistry; Redox reactions; Redox‐active ligands; Solvents; Valence tautomerism
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201800525

Intramolecular electron transfer (IET) processes between the metal and a redox‐active ligand in a transition‐metal complex are currently intensively studied, as they represent key steps of some redox‐catalytic reactions in synthetic chemistry and of some enzymatic redox reactions in biological systems. Using a combination of experimental results and quantum chemical calculations, we herein examine in detail the role of the solvent polarity and seemingly small modifications at the redox‐active ligand on IET processes in mononuclear copper complexes with redox‐active bisguanidine ligands. A direct and simple correlation between the coordination mode and the electronic structure in these complexes is established, assisting in the fine‐tuning of the ligand properties for optimal promotion of IET. Intramolecular metal–ligand electron transfer processes in mononuclear copper complexes with redox‐active bisguanidine ligands can be controlled by the solvent polarity, as disclosed by a combination of experimental work and quantum chemical calculations.