Neutral Aminyl Radicals Derived from Azoimidazolium Dyes

The
synthesis and characterization of a new class of neutral aminyl
radicals is reported. Monoradicals were obtained by reduction of azoimidazolium
dyes with potassium. Structural, spectroscopic, and computational
data suggest that the spin density is centered on one of the nitrogen
atoms of the former azo group. The reduction of a dimeric dye with
an octamethyl­biphenylene bridge between the azo groups resulted
in the formation of a biradical with largely independent unpaired
electrons. Both the monoradicals and the biradical were found to display
high stability in solution as well as in the solid state.