A multi-step procedure for evaluating the EPR parameters of indolinonic aromatic aminoxyls: A combined DFT and spectroscopic study

A DFT study on indolinonic aromatic aminoxyls has been carried out at different levels of theory. The comparison with previous experimental data from ENDOR, X-rays and PND (polarized neutron diffraction) techniques confirms that such a computational approach represents an important aid for understanding the properties of this class of aminoxyls such as hyperfine coupling constants (hfcc), isotropic g-factors, spin density distributions and geometries. At first, a model compound was studied with different model chemistries; B1LYP, B3LYP and PBE0 hybrid functionals were employed in conjunction with various medium to large size basis sets. The study outlines that none of the model chemistries considered is able to correctly describe the EPR features of these radicals by itself. For this reason, by taking into account a compromise between accuracy and computational cost, a multi-step procedure was checked over a homogeneous series of indolinonic aminoxyls and then proposed.