Transformation-induced evolution of far-infrared vibrational modes in theophylline

Abstract

Time-resolved terahertz (THz) spectroscopy has been used to characterize polymorphic transformations in crystalline theophylline, a widely used pharmaceutical compound. On transformation, different inter-molecular bonding arrangements arise, leading to distinct THz spectral signals. Changes between polymorphic forms were confirmed by IR and powder X-ray diffraction measurements.