Using terahertz spectroscopy and solid-state density functional theory to characterize a new polymorph of 5-(4-pyridyl)tetrazole

A new high-temperature polymorph of 5-(4-pyridyl)tetrazole has been discovered and characterized using X-ray crystallography and terahertz (THz) spectroscopy. The THz spectrum of the new polymorph was compared to the previously published form and was replicated by means of solid-state density functional theory. Terahertz spectroscopy was used to determine the influence of the different packing motifs on the molecular and low energy lattice vibrations displayed in the region from 10 to 100 cm^-1. It was found that there is only a ∼2 cm^-1 difference in the primary peak location, caused by a whole molecule rotation along the principal a axis, between the two polymorphic forms. In addition, the energy of formation was determined, and it was found that the previously known polymorphic form is more stable by ∼0.25 kJ/mol, compared to the newly discovered form.