Ab Initio Study of Nitroxyl and Imino Nitroxides. Relation Between Electronic Structure and Magnetic Properties in Metal-Nitroxide Complexes

A complete ab initio optimization of the simplest nitronyl and imino nitroxides was performed at the UHF-SCF level, using a 3-21G basis set. The molecular electrostatic potential maps were drawn and correctly predict the coordinating ability of oxygen and nitrogen in both radicals. The largest fraction of the unpaired electron is always found on the oxygens, but the imino nitrogen bears a noticeable part of the spin population in agreement with experimental findings. All the trends of experimental EPR spectra are well reproduced by the calculated spin-projected densities at nuclei, the imino nitrogen being found to have the largest coupling const. at the SCF le