Characterization of copper complexes with derivatives of the ligand (2-aminoethyl)bis(2-pyridylmethyl)amine (uns-penp) and their reactivity towards oxygen

• Published in: Journal of inorganic biochemistry Vol. 223; p. 111544
• Main Authors: Brückmann, Tim, Becker, Jonathan, Würtele, Christian, Seuffert, Marcel Thomas, Heuler, Dominik, Müller-Buschbaum, Klaus, Weiß, Morten, Schindler, Siegfried
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.10.2021
• Subjects: Coordination Complexes - chemical synthesis; Coordination Complexes - chemistry; Copper - chemistry; Copper complex; Dioxygen activation; Ligands; Molecular Structure; Oxidation-Reduction; Oxygen - chemistry; Peroxido complex; Pyridines - chemical synthesis; Pyridines - chemistry; Stopped-flow; Superoxido complex; Tripodal ligands; Superoxido complex; Peroxido complex; Tripodal ligands; Copper complex; Dioxygen activation; Stopped-flow
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2021.111544

A series of copper(I) complexes with ligands derived from the tripodal ligand (2-aminoethyl)bis(2-pyridylmethyl)amine (uns-penp) have been structurally characterized and their redox chemistry analyzed by cyclic voltammetry. While the redox potentials of most of the complexes were similar their reactivity towards dioxygen was quite different. While the complex with a ferrocene derived ligand of uns-penp reacted in solution at low temperatures in a two-step reaction from the preliminary formed mononuclear end-on superoxido complex to a quite stable dinuclear peroxido complex it did not react with dioxygen in the solid state. Other complexes also did not react with dioxygen in the solid state while some showed a reversible formation to a green compound, indicating formation of an end-on superoxido complex that unfortunately so far could not be characterized. In contrast, copper complexes with the Me2uns-penp and Et-iProp-uns-penp formed dinuclear peroxido complexes in a solid-state reaction. While the reaction of dioxygen with the [Cu(Me2uns-penp]BPh4 was quite slow an instant reaction took place for [Cu(Et-iProp-uns-penp]BPh. Very unusual, it turned out that crystals of the copper(I) complex that could be structurally characterized still were crystalline when reacted with dioxygen. Therefore, it was possible to solve the structure of the corresponding dinuclear peroxido complex directly from the same batch of crystals. The crystalline structures of the copper(I) and copper(II) complex revealed that the reason for this is the fact, that the copper(I) complex is kind of preorganized for the uptake of dioxygen and does not really change in its overall structure when being oxidized. During a systematic study of the reactivity of a series of copper(I) complexes with tripodal ligands towards dioxygen a crystalline transformation of a copper(I) complex to the corresponding end-on peroxido complex was observed. [Display omitted] •Detailed study on the reactivity of copper(I) complexes towards dioxygen.•Low temperature UV–vis studies to detect labile “dioxygen adduct” copper complexes.•Optimization of ligand system to obtain more stable peroxido copper complexes.•Solid state reactions of copper(I) complexes with dioxygen.•Molecular structure of an end-on copper peroxido complex.