Two-State Hydrogen Atom Transfer Reactivity of Unsymmetric [Cu2(O)(NO)]2+ Complexes
Samantha Carter1, Wenjie Tao1, Rajat Majumder1
1Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States.
Journal of the American Chemical Society
|August 4, 2023
Summary
Temperature influences dicopper oxo nitrosyl ([Cu2(O)(NO)]2+) complexes, switching spin states and affecting hydrogen atom transfer (HAT) reactivity. The S=1/2 isomer drives HAT, and asymmetric environments enhance reaction rates.
Area of Science:
- Inorganic Chemistry
- Bioinorganic Chemistry
- Physical Chemistry
Background:
- Dicopper oxo nitrosyl ([Cu2(O)(NO)]2+) complexes exhibit temperature-dependent spin states.
- Hydrogen atom transfer (HAT) is a fundamental reaction in chemistry and biology.
- Understanding spin state influence on reactivity is crucial for catalyst design.
Purpose of the Study:
- To investigate the temperature-dependent spin switching of [Cu2(O)(NO)]2+ complexes.
- To elucidate the relationship between spin states and hydrogen atom transfer (HAT) reactivity.
- To explore strategies for controlling HAT rates using coordination environment modifications.
Main Methods:
- Electron paramagnetic resonance (EPR) spectroscopy to analyze spin states.
- Evans method for magnetic susceptibility measurements.
- Kinetic studies to determine HAT rates (kHAT).
Main Results:
- [Cu2(O)(NO)]2+ complexes transition from S=1/2 to S=3/2 around 202 K.
- A strong correlation (R2=0.988) was found between HAT rate and the S=1/2 state population at 198 K.
- Asymmetric coordination environments accelerate HAT rates by perturbing spin equilibria.
Conclusions:
- HAT by [Cu2(O)(NO)]2+ complexes is primarily mediated by the S=1/2 isomer.
- Modulating spin equilibria through coordination environment design can control HAT reactivity.
- Metalloenzymes may utilize similar strategies to regulate HAT reactions in biological systems.
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