14N Quadrupole Cross-Relaxation Spectroscopy of a Compound of Pharmacological Interest

Abstract

Cross-relaxation spectroscopy has been used to record the 14N quadrupole resonance spectrum of two of the polymorphic forms of the pharmacologically-important compound: 2-4-(5-Bromo- 3-methylpyrid-2-yl)butylammo-5-(6-methylpyrid-3-yl)methyl-pyrimidin-4-one. Three 14N frequencies for four of the non-equivalent nitrogen sites within the molecule have been identified by combined irradiation and cross-relaxation techniques and quadrupole coupling constants and asymmetry parameters deduced therefrom; the absence of 14N (and 79Br) signals from the bromine-substituted pyridine ring suggests that this part of the molecule is disordered in the crystal. The spectral intensities have been used to derive approximate values for the 14N and 1H relaxation times, which show clear differences between the two polymorphs.