Electronic structures of pyridine N-oxide and 4-nitrosopyridine N-oxide

The -electron structure of pyridine N-oxide was calculated by the Pariser-Parr-Pople method, the effect of -polarization of the NO bond upon the valence state ionization potentials and electron affinities being taken into account. By the aid of these results, the -electron structure of 4-nitrosopyridine N-oxide was studied by the composite system method. The calculated transition energies and oscillator strengths can satisfactorly explain the observed electronic absorption spectrum. The 372 m band was ascribed to the charge-transfer transition from the oxygen atom of the NO group to the nitroso group via the pyridine nucleus.