Changes in the IR spectra and structures of pyridine-3-carboxamides-d0 and -d2 caused by their conversion into azanions-d0 and -d1: Experimental and computational studies

The IR spectral and structural changes caused by conversions of pyridine-3-carboxamide (nicotinamide)-d0 and -d2 into azanions-d0 and -d1 have been studied by means of both spectroscopic experiments and B3LYP force field computations. In agreement between theory and experiment, the conversions cause a 184 cm−1 decrease in the carbonyl stretching frequency, 13.2-fold increase in the integrated intensity of the 8a-type pyridyl ring band and other essential spectral changes. According to the calculations, the strongest changes in the steric structure, caused by the conversion, take place at and next to the azanionic center. The non-planar (twisted) nicotinamide molecule converts into a planar azanion. Nearly half of the new (azanionic) charge remains localized at the azanionic center.