Hybrid density functional approach to the structures and EPR parameters of σ-type iminoxy radicals: the case of 3-oxobutan-2-iminoxyl

Hybrid density functional calculations are used to study geometries together with 1H, 13C, 14N and 17O isotropic hyperfine coupling constants for the 3-oxabutan-2-iminoxy radical. The effect of 12 different basis sets on the calculated hyperfine parameters is investigated. Particular emphasis is placed on the performance of the B3LYP functional in the description of the unpaired electron interaction with the iminoxy 17O nucleus. It is found that the EPR-III basis sets of Barone and TZVP of Godboud and Andzelm lead to the best quantitative agreement between theoretical and experimental hyperfine constants; the mean absolute deviation from experiment for 13C, 14N and 17O is ca. 2 G.