DFT calculation of isotropic hyperfine coupling constants of spin adducts of 5,5-dimethyl-1-pyrroline-N-oxide in benzene and water

Isotropic hyperfine coupling constants (HFCCs) of spin adducts of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) are calculated by DFT method with solvation effect. Geometries of ring conformers and rotational conformers of trapped radicals are optimized and their HFCCs are calculated. Boltzmann weighted average of HFCCs of low energy conformations shows very good agreement with the experimental value in benzene. Two or four water molecules hydrogen bonded to the spin adduct have to be explicitly incorporated in the case of water. The results show time-independent averaging of relevant conformers is a very practical method for calculation of HFCCs of DMPO spin adducts. (C) 2017 Elsevier B.V. All rights reserved.