Fully Delocalized Mixed-Valent Cu1.5 Cu1.5 Complex: Strong Cu-Cu interaction and Fast Electron Self-Exchange Rate Despite Large Structural Changes

Yang Liu; Stefan G Resch; Haowei Chen; Sebastian Dechert; Serhiy Demeshko; Eckhard Bill; Shengfa Ye; Franc Meyer

doi:10.1002/anie.202215840

Fully Delocalized Mixed-Valent Cu^1.5 Cu^1.5 Complex: Strong Cu-Cu interaction and Fast Electron Self-Exchange Rate Despite Large Structural Changes

Angew Chem Int Ed Engl. 2023 Mar 1;62(10):e202215840. doi: 10.1002/anie.202215840. Epub 2023 Jan 25.

Authors

Yang Liu¹, Stefan G Resch¹, Haowei Chen^{2

3}, Sebastian Dechert¹, Serhiy Demeshko¹, Eckhard Bill⁴, Shengfa Ye², Franc Meyer¹

Affiliations

¹ Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, 37077, Göttingen, Germany.
² State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, P. R. China.
³ Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
⁴ Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470, Mülheim an der Ruhr, Germany.

PMID: 36504436
DOI: 10.1002/anie.202215840

Abstract

A flexible macrocyclic ligand with two tridentate {CNC} compartments can host two Cu ions in reversibly interconvertible states, Cu^I Cu^I (1) and mixed-valent Cu^1.5 Cu^1.5 (2). They were characterized by XRD and multiple spectroscopic methods, including EPR, UV/Vis absorption and MCD, in combination with TD-DFT and CASSCF calculations. 2 features a short Cu⋅⋅⋅Cu distance (≈2.5 Å; compared to ≈4.0 Å in 1) and a very high delocalization energy of 13 000 cm^-1 , comparable to the mixed-valent state of the biological Cu_A site. Electron self-exchange between 1 and 2 is rapid despite large structural reorganization, and is proposed to proceed via a sequential mechanism involving an active conformer of 1, viz. 1'; the latter has been characterized by XRD. Such electron transfer (ET) process is reminiscent of the conformationally gated ET proposed for biological systems. This redox couple is a unique pair of flexible dicopper complexes, achieving fast electron self-exchange closely related to the function of the Cu_A site.

Keywords: Conformational Change; CuA Site; Electron Self-Exchange; Macrocyclic Ligands; Mixed-Valent Cu1.5Cu1.5.

Abstract

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