Source:Magnetic Resonance in Chemistry, John Wiley & Sons, Ltd., 27:88–91, 1989
14N NMR data and semiempirical molecular orbital calculations are reported for dibenzo-[1,3a,4,6a]tetrazapentalene (1). The 14N signals were assigned by means of the results of the molecular orbital calculations and measured relative signal widths. A comparison was made with results for some azolopyridines. A linear correlation was obtained between the nitrogen shieldings, expressed with respect to the bridging nitrogen atom, and the corresponding relative charge densities. Thus nitrogen nuclear shielding results provide a good estimation of electron charge distribution in these molecules. Compound 1 provides the first case in which the shielding of a pyridine-type nitrogen atom is greater than that of the indolizine-type nitrogen.