Resonance Raman spectrum of the 4, 4′‐bipyridine radical anion

Resonance Raman, ESR and visible absorption spectra have been observed at room temperature for the 4, 4′‐bipyridine radical anion in tetrahydrofuran and for 4, 4′‐bipyridine adsorbed on metallic potassium. Based on the quinoid structure of the radical anion, as predicted by the MO theory, a normal coordinate analysis has been carried out. The relative Raman intensities have also been calculated satisfactorily for the totally symmetric modes of the radical anion. Thus, the main Raman bands are interpreted in terms of the molecular structure change caused by the resonant electronic transition in the visible region. The results are compared with those of the biphenyl radical anion, 2,2′‐bipyridine radical anion and the methylviolegen radical cation reported in the literature.