Characterization of Monomeric Mn II/III/IV –Hydroxo Complexes from X- and Q-Band Dual Mode Electron Paramagnetic Resonance (EPR) Spectroscopy
Year: 2013
Type: article
Abstract: Manganese-hydroxo species have been implicated in C-H bond activation performed by metalloenzymes, but the electronic properties of many of these intermediates are not well characterized. The present work presents a detailed characterization of three Mn(n)-OH complexes (where n = II, III, and IV) of the tris[(N'-tert-butylureaylato)-N-ethylene]aminato ([H3buea](3-)) ligand using X- and Q-band dual mode electron paramagnetic resonance (EPR). Quantitative simulations for the [Mn(II)H3buea(OH)](2-) complex demonstrated the ability to characterize similar Mn(II) species commonly present in the resting states of manganese-containing enzymes. The spin states of the Mn(III) and Mn(IV) complexes determined from EPR spectroscopy are S = 2 and 3/2, respectively, as expected for the C3 symmetry imposed by the [H3buea](3-) ligand. Simulations of the spectra indicated the constant presence of two Mn(IV) species in solutions of [Mn(IV)H3buea(OH)] complex. The simulations of perpendicular- and parallel-mode EPR spectra allow determination of zero-field splitting and hyperfine parameters for all complexes. For the Mn(III) and Mn(IV) complexes, density functional theory calculations are used to determine the isotropic Mn hyperfine values, to compare the excited electronic state energies, and to give theoretical estimates of the zero-field energy.
Source: Inorganic Chemistry
DOI: 10.1021/ic401681r
Institutions: Carnegie Mellon University, University of California, Irvine
Language: English
Subfield: Inorganic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2329070983