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Keywords:

  • g-tensors;
  • hydrogen bonding;
  • semiquinone anion radicals;
  • EPR spectroscopy

Abstract

We report results of systematic g-tensor calculations of hydrogen-bonded complexes of two benchmark semiquinone anion radicals, 1,4-benzoquinone and tetramethyl-1,4-benzoquinone (duroquinone), with water and methanol molecules. The calculations have been carried out with the help of a recently developed g-tensor module that is based on a relativistic density functional method that takes spin–orbit interaction self-consistently into account. We demonstrate the applicability of this new computational scheme to describe quantitatively delicate effects of hydrogen bonding on electronic g-tensor values. Also, we explored general trends of how g-tensors depend on the structure and stoichiometry of hydrogen-bonded semiquinone complexes. Complexes exhibiting one hydrogen bond per oxygen atom of the quinones with a linear arrangement of the C[DOUBLE BOND]O … H moieties were shown to feature g-shifts induced by these hydrogen bonds that are in close agreement with measured electron paramagnetic resonance data. Based on deviations of calculated and measured g-components, we classify all other model complexes studied as less probable under the experimental conditions. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002