Ultraviolet and Spin Resonance Spectra of Nitropyridines and Nitropyridine N-Oxides

The esr and uv spectra of 2-, 3-, and 4-nitropyridine and 2-, 3-, and 4-nitropyridine N-oxide anion radicals in solution have been measured as well as the uv spectra of 2-, 3-, and 4-nitropyridine N-oxide neutral molecules in the same solvent. The results have been interpreted by application of a number of semiempirical quantum mechanical methods. By comparison of experimental and calculated data an assignment of visible and ultraviolet absorption bands to electronic transitions and of hyperfine splitting (hfs) coupling constants to magnetic nuclei is proposed.