Fully Delocalized Mixed‐Valent Cu1.5Cu1.5 Complex: Strong Cu‐Cu interaction and Fast Electron Self‐Exchange Rate Despite Large Structural Changes. Issue 10 (25th January 2023)

• Record Type: Journal Article
• Authors: Liu, Yang; Resch, Stefan G.; Chen, Haowei; Dechert, Sebastian; Demeshko, Serhiy; Bill, Eckhard; Ye, Shengfa; Meyer, Franc
• Is Part Of: Angewandte Chemie international edition. Volume 62:Issue 10(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-25
• Subjects: Conformational Change -- CuA Site -- Electron Self-Exchange -- Macrocyclic Ligands -- Mixed-Valent Cu1.5Cu1.5; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202215840
• Languages: English
• ISSNs: 1433-7851

Abstract

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 CuA 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 CuA site. Abstract : Dicopper complexes in the Cu I Cu I and mixed‐valent Cu 1.5 Cu 1.5 states have been synthesized and comprehensively characterized, revealing a high delocalization energy of the mixed‐valent species comparable with the biological CuA site. Fast electron self‐exchange is suggested to occur via a sequential ET pathway, involving an active conformational isomer of the flexible Cu I Cu I species, pointing to a potential gating scenario for ET.