Pharmaceutical Cocrystal of Ethenzamide with Gallic Acid: Structural Investigation Based on Terahertz Spectroscopy and DFT Calculation

The pharmaceutical cocrystal of ethenzamide (ETZ) with gallic acid (GA) was synthesized by the solvent evaporation method. Terahertz (THz) spectroscopy and density functional theory (DFT) were used to explore cocrystal molecular structures and vibrational mode attribution. The THz spectrum showed distinctly different characteristic peaks between the cocrystal and its original components, indicating the formation of the cocrystal. Furthermore, simulations showed that the ETZ-GA cocrystal forms O-H$\cdots$O hydrogen bonds and interacts through the -OH in the GA and oxygen of amide group in the ETZ molecule.