报告题目：Kinetic Isotope Effect and Tunneling:
Effective Probes of the Reactive-Spin-State and the Stereo Chemistry of the Transition State During Hydrogen Abstraction Reactions of Oxoiron (IV) Complexes and Enzymes
报告人：Prof. Sason Shaik
The Hebrew University of Jerusalem, Israel
Two-state and multi-state reactivity (TSR and MSR) are ubiquitous in chemistry and in nature. These reactivity patterns, which involve more than one spin state, are found by now, starting from oxidation reactions of the tiny oxo-iron diatomic all the way to Cytochrome P450 enzymes, nonheme enzymes and synthetic oxo-metal analogs. Furthermore, it turns out that many bond activation reactions by closed- shell catalysts also involve TSR/MSR.
Despite the current popularity of the TSR/MSR concepts among chemists, the spin crossover does not have as yet a clear kinetic signature, which makes the idea somewhat abstract from practicing chemists. Is there a way to find clear kinetic signatures of such reactivity patterns? This is the main question I would answer in my talk: Yes, such a signature is in fact available. The talk will demonstrate that kinetic isotope effect (KIE) with tunneling correction [KIETC] constitutes a reliable signature of the following:
•The reactive spin state
•The structure of the transition state (TS)
•The orbital (s) which control these structures
•The ligand constitution of the TS.
Examples will be shown for synthetic oxo-iron species and P450 enzymes.
 Mandal, Mallick and Shaik, Acc. Chem. Res. 2018, 51, 107.