Radical anions of pyridine derivatives

Pyridine radical anion, generated by alkali-metal reduction of pyridine shows an absorption maximum around 340 nm, the actual position varying with the counter-cation. The change in the spectra of the pyridine radical anion with time is due to formation of radical anions and dianions of 4,4′-, and 2,2′-bipyridyls. Alkylpyridines with substituents in the 3- or 4-position form stable radical anions which do not undergo dimerization. Electron-withdrawing groups produce a bathochromic shift of the absorption band of the pyridine radical anion.