O- and C-Adducts of 5-(het)aryl-2,3-dicyano-1-ethylpyrazinium salts are latent sources of biradicals capable of forming tetraazaphenanthrene derivatives via dimerization. The mechanisms of the reactions were examined using ESR spectroscopy. The stereochemistry of the resulting heterocyclic systems was studied by NMR spectroscopy. The crystallographic data on their three-dimensional structures were obtained