Two-State Hydrogen Atom Transfer Reactivity of Unsymmetric [Cu2(O)(NO)]2+ Complexes

Samantha Carter; Wenjie Tao; Rajat Majumder; Alexander Yu Sokolov; Shiyu Zhang

doi:10.1021/jacs.3c04510

Two-State Hydrogen Atom Transfer Reactivity of Unsymmetric [Cu₂(O)(NO)]²⁺ Complexes

J Am Chem Soc. 2023 Aug 16;145(32):17779-17785. doi: 10.1021/jacs.3c04510. Epub 2023 Aug 4.

Authors

Samantha Carter¹, Wenjie Tao¹, Rajat Majumder¹, Alexander Yu Sokolov¹, Shiyu Zhang¹

Affiliation

¹ Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States.

PMID: 37540110
DOI: 10.1021/jacs.3c04510

Abstract

We report the temperature-dependent spin switching of dicopper oxo nitrosyl [Cu₂(O)(NO)]²⁺ complexes and their influence on hydrogen atom transfer (HAT) reactivity. Electron paramagnetic resonance (EPR) and Evans method analysis suggest that [Cu₂(O)(NO)]²⁺ complexes transition from the S = 1/2 to the S = 3/2 state around ca. 202 K. At low temperatures (198 K) where S = 3/2 dominates, a strong correlation between the rate of HAT (k_HAT) and the population of the S = 1/2 state was identified (R² = 0.988), suggesting that the HAT by [Cu₂(O)(NO)]²⁺ complexes proceeds by the S = 1/2 isomer. Installation of functional groups that introduce an unsymmetric secondary coordination environment accelerates the HAT rates through perturbation of the spin equilibria. Given the often unsymmetric coordination sphere of bimetallic active sites in natural proteins, we anticipate that similar strategies could be employed by metalloenzymes to control HAT reactions.