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

Abstract

X-ray data for ortho, meta and para nitraminopyridine N-oxides are compared with the structures obtained using semi-empirical AM1, PM3 and MNDO calculations. The calculated vibrational frequencies and potential energy distribution are used in the analysis of the IR and Raman spectra. The spectra of the molecular complex formed between the ortho derivative and methylamine are discussed. The characteristic vibrational features, observed for all compounds around 3000–2400 and 1800cm−1, are assigned to the ν(N–H⋯O) stretching modes on Fermi resonance, with the overtone of the out-of-plane bending mode 2γ(N–H⋯O).