Multifrequency, multitechnique pulse EPR spectroscopy was employed to unravel the spin Hamiltonian parameters of 17O in the [FeVO] moiety with two different tetraamido macrocyclic ligands (TAMLs), [FeV(O)(TAML-1)]- (1, H4(TAML-1) = 3,4,8,9-tetrahydro-3,3,6,6,9-hexamethyl-1H-1,4,8,11-benzotetraazocyclotridecane-2,5,7,10-(6H,11H)-tetrone) and [FeV(O)(TAML-2)]- (2, H4(TAML-2) = H4[(Me2CNCOCMe2NCO)2CMe2]), to investigate the electronic structure of FeV-oxo species. Although rigorous computational studies on high-valent iron-oxo species have been reported recently, experimental evidence to explicate the electronic structure of FeV-oxo species is sparse. In particular, a complete hyperfine tensor of 17O can hardly be detected. Herein, we successfully probed the hyperfine tensor of 17O of the FeV-oxo moiety using ENDOR spectroscopy. Hence, the EPR spectroscopic results reported here provide a conclusive experimental basis for elucidating the electronic structure of the FeV-oxo complex. Moreover, the reactivity of the two different complexes is very distinct, and our results may provide insight into how their electronic structure contributes to their reactivity.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF-2017M3D1A1039380 and NRF-2020R1F1A1069151) and KBSI grant C1300000 to S. H. K. This work was also supported by the NRF of Korea through CRI (NRF-2012R1A3A2048842 to W. N.) and the Basic Science Research Program (NRF-2020R1I1A1A01074630 to Y.-M. L.).
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