Experimental and Theoretical Investigations of the Existence of CuII, CuIII, and CuIV in Copper Corrolato Complexes

• Published in: Angewandte Chemie International Edition 2015-11, Vol.54 (46), p.13769-13774
• Main Authors: Sinha, Woormileela, Sommer, Michael G., Deibel, Naina, Ehret, Fabian, Bauer, Matthias, Sarkar, Biprajit, Kar, Sanjib
• Format: Article
• Language: English
• Subjects: Catalysis; Copper; copper corroles; EPR spectroscopy; higher oxidation states; Oxidation; spectroelectrochemistry; XANES measurements
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201507330

The most common oxidation states of copper in stable complexes are +I and +II. CuIII complexes are often considered as intermediates in biological and homogeneous catalysis. More recently, CuIV species have been postulated as possible intermediates in oxidation catalysis. Despite the importance of these higher oxidation states of copper, spectroscopic data for these oxidation states remain scarce, with such information on CuIV complexes being non‐existent. We herein present the synthesis and characterization of three copper corrolato complexes. A combination of electrochemistry, UV/Vis/NIR/EPR spectroelectrochemistry, XANES measurements, and DFT calculations points to existence of three distinct redox states in these molecules for which the oxidation states +II, +III, and +IV can be invoked for the copper centers. The present results thus represent the first spectroscopic and theoretical investigation of a CuIV species, and describe a redox series where CuII, CuIII, and CuIV are discussed within the same molecular platform. Fly high: Electrochemical, UV/Vis/NIR/EPR spectroelectrochemical, and XANES measurements as well as DFT calculations point to the existence of three distinct redox states in the title compounds as oxidation states of +II, +III, and +IV can be invoked for the copper centers. These results thus represent the first spectroscopic and theoretical investigation of a CuIV species.