Investigation of a C(sp²)-coupled nitronyl nitroxide diradical by electron paramagnetic resonance

A heteroatomic analog of 1,1,2,3,3-pentamethylenepropane, the diradical N-[bis(4,4,5,5-tetramethyl-3-oxide-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)methylene]-2-methylpropane-2-amine oxide (1) with two C(sp²)-bonded nitronyl nitroxide fragments in magnetically concentrated (single crystal) and magnetically diluted (frozen solution) forms was studied by EPR spectroscopy. The longitudinal and transverse relaxation times of diradical 1 in the frozen solution were measured for the first time; a significant difference in the intramolecular exchange interaction was demonstrated for the cases of the single crystal and the frozen solution. The influence of solvation on the value of the intramolecular exchange interaction in this class of compounds was discussed.