Paramagnetic rings neutral radicals

The one-electron reduction of phospholium salts llla-c has been studied by electron paramagnetic resonance (EPR) and DFT calculations, which conclude that they are good electron acceptors <2006PCP862>. Their reduction affords neutral radicals where the unpaired electron is mainly delocalized over the carbon skeleton of the P-ring. These compounds have been characterized in the solid state by X-ray diffraction and exhibit metric data that are typical of this type of compound (see Table 11). 

When the dithiole ring is annelated by phenalene, the laws of valence require the resultant aromatic heterocycle to be cationic reduction thus gives the neutral phenaleno[l,9-c(/][l,2]dithiolyl radical (138). This persistent radical has been examined in solution and its hyperfine splittings assigned on the basis of MO calculations. The radical is remarkably stable against dimerization it may be isolated as a paramagnetic solid whose mass... 

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