Isotropic hyperfine splitting in the nitroxide radicals 4-amino-2,2,5,5-tetramethyl-3-imidazoline-N-oxyl and 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl

Experimentally measured and DFT calculated isotropic hyperfine splitting constants for the nitroxide radicals 4-amino-2,2,5,5- tetramethyl-3-imidazoline-N-oxyl and 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl were compared to provide the basis for a choice of an appropriate level of low-cost DFT computations of electronic characteristics of nitroxide radicals.