Electronic spectra of 2-N-substituted derivatives of 2-amino-4-nitropicolines -: I.: 2-alkylamino-3- (or -5)-methyl-4-nitropyridine N-oxides

The UV spectra of 2-methyl- and 2-ethylamino-3- (or -5)-methyl-4-nitropyridine N-oxides in ethanol have been examined and compared with results (transition energies, intensities) of modified INDO calculations in order to make the assignment of allowed bands. The influence of substituents in the molecule on lambda(max) and epsilon(max) of spectral bands is discussed. The electronic spectra of 2-alkylamino-3- (or -5)-methyl-4-nitropyridine N-oxides and the effect of steric hindrance on the spectra are interpreted. The preparation procedure of four new 2-alkylamino-4-nitropicoline N-oxides is described.