The complete 14N NQR spectra have been measured in the two polymorphic crystalline phases of the molecular complex isonicotinamide oxalic acid (2:1) by nuclear quadrupole double resonance. The observed NQR parameters have been assigned to the two nitrogen positions (ring and amide) in a molecule and analyzed in a model, where it is assumed that an additional electric charge on the nitrogen atom changes the NQR parameters. The model suggests that this additional electric charge is negative so that the N H O hydrogen bond seem to be partially ionic, of the type N...H-O.
COBISS.SI-ID: 2274660
The 1,3,4-thiadiazole derivatives have been studied experimentally in the solid state by 1H–14N NQDR spectroscopy and theoretically by Density Functional Theory (DFT). The specific pattern of the intra and intermolecular interactions in 1,3,4-thiadiazole derivatives is described within the QTAIM (Quantum Theory of Atoms in Molecules)/DFT formalism. The results obtained suggest that considerable differences in the NQR parameters permit differentiation even between specific pure association polymorphic forms and indicate that the stronger hydrogen bonds.
COBISS.SI-ID: 2267236