Structural and vibrational data obtained from experimental (X-ray, IR and Raman) and AM1, PM3 and MNDO semi-empirical methods for ortho meta and paranitraminopyridine N-oxides

X-ray data for ortho, meta and para nitraminopyridine N-oxides are compared with the structures obtained using semiempirical AM1, PM3 and MNDO calcula tions. The calculated vibrational frequencies and potential energy distribu tion are used in the analysis of the IR and Raman spectra. The spectra of t he molecular complex formed between the ortho derivative and methylamine ar e discussed. The characteristic vibrational features, observed for all comp ounds around 3000-2400 and 1800 cm(-1), are assigned to the nu (N-H . . .O) stretching modes on Fermi resonance, with the overtone of the out-of-plane bending mode 2 gamma (N-H . . .O). (C) 2001 Elsevier Science B.V. All righ ts reserved.