¹⁵N NMR spectroscopy of some azines

Abstract

Abstract 15 N NMR shielding data are presented for 56 cyclic azines in 0.5 M dimethyl sulfoxide solutions with 0.01 M increments of Cr(acac) 3 added for each nitrogen atom in the molecules. For the polyazines, the 15 N signal assignments were based on 2 J (NH) interactions and some INDO/S‐SOS shielding calculations. The effects of α‐, β‐ and γ‐methyl and conjugated ring substitution on nitrogen shielding are presented and discussed, as are the influences arising from fusion with alicyclic and aromatic rings at various positions. The effects of a second nitrogen atom on the shielding of the first one are shown to be critically dependent on both their relative positions and on the position of fusion of conjugated ring systems.