The average excitation energy approximation, used in conjunction with INDO molecular orbital calculations, is shown to give a quantitative correlation between the experimental nitrogen chemical shifts of some azine ring systems and the calculated values of the local paramagnetic term. The molecules studied include pyridine, three isomeric diazines, 1,3,5-triazine, and 1,2,4,5-tetrazine. The results obtained compare favorably with previous estimates of the nitrogen nuclear screening in these molecules. © 1974.
Witanowski, M., Stefaniak, L., Januszewski, H., & Webb, G. A. (1974). Nitrogen NMR chemical shifts of some simple azines interpreted by INDO molecular orbital calculations. Journal of Magnetic Resonance (1969), 16(1), 69–74. https://doi.org/10.1016/0022-2364(74)90200-5