A restricted Hartree-Fock calculation of the spin density distribution and the ionization potentials of the benzyl, aminophenyl, and phenoxy radicals

Mestechkin, M. M.; Poltavets, V. N.; Degtyarev, L. S.; Pokhodenko, V. D.

doi:10.1007/bf00519793

Cited by 1 publication

(2 citation statements)

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“…24,25 Earlier studies show that restricted Hartree-Fock reference states yield satisfactory results for several substituted benzene radicals except for the phenoxyl radical. 30,36 This discrepancy is explained by a complex electronic structure with strong correlation, and to the presence of low-lying excited states. However, MCSCF wave functions with cc-pVDZ basis set yield g-values consistent with experiments.…”

Section: Resultsmentioning

confidence: 99%

“…An experimental geometric structure is not available for the phenoxyl radical. Unfortunately, various problems connected with the determination of a proper CO bond length are reported in the literature. ,,− Calculations based upon different methods (Restricted Open shell Hartree−Fock (ROHF), UHF, MCSCF, Density Functional Theory (DFT)) generate bond lengths in the range 1.22−1.38 Å. Predictions of the ground-state symmetry strongly depend on the starting guess for zero-iteration, and two main predictions for the ground state of the phenoxyl radical are reported.…”

Section: Resultsmentioning

confidence: 99%

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Hydrogen Bonding to Tyrosyl Radical Analyzed by Ab Initio g-Tensor Calculations

et al. 2000

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Hydrogen bonding to the tyrosyl radical in ribonucleotide reductase (RNR) has been simulated by a complex between the phenoxyl radical and a water molecule. Multiconfigurational self-consistent field linear response theory was used to calculate the g-tensor of the isolated phenoxyl radical and of the phenoxyl−water model. The relevance of the model was motivated by the fact that spin density distributions and electron paramagnetic resonance (EPR) spectra of the phenoxyl and tyrosyl radicals are very similar. The calculated g-tensor anisotropy of the phenoxyl radical was comparable with experimental findings for tyrosyl in those RNRs where the H-bond is absent: g x = 2.0087(2.0087), g y = 2.0050(2.0042), and g z = 2.0025(2.0020), where the tyrosyl radical EPR data from Escherichia coli RNR are given in parentheses. The hydrogen bonding models reproduced a shift toward a lower g x value that was observed experimentally for mouse and herpes simplex virus RNR where the H-bond was detected by electron−nuclear double resonance after deuterium exchange. This decrease could be traced to lower angular momentum and spin-orbit coupling matrix elements between the ground 2 B 1 and the first excited 2 B 2 states (oxygen lone-pair n to πSOMO excitation) upon hydrogen bonding in a linear configuration. The g x value was further decreased by hydrogen bonding in bent configurations due to a blue shift of this excitation.

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Section: Resultsmentioning

confidence: 99%