Vibrational spectra and molecular structure of 4,4′-azobis(pyridine N-oxide)

The vibrational and electron absorption spectra of 4,4′-azobis(pyridine N-oxide) have been studied with the help of density functional theory calculations to gain information on the molecular structure in solution. The molecules assume a trans-planar conformation in non-polar solvents, with a strong conjugation between the π electrons of the heteroaromatic rings and of the NN double bond. In polar solvents the molecules have still a center of symmetry, but the rings are not coplanar.