High-pressure polymorphism in amoxicillin

[Display omitted] •The polymorphic transformation of amoxicillin under high pressure.•The amoxicillin sample underwent two phase transitions at 2.71 GPa and 7.45 GPa.•High pressure led to restructuring of the molecular layering in amoxicillin.•High pressure-induced polymorphic transformations of amoxicillin were reversible. This work is devoted to the pressure-induced structural transformations of amoxicillin by Raman and infrared spectroscopy at pressures up to 10 GPa. The Raman and infrared results indicate that amoxicillin underwent two phase transitions upon compression, specifically phase α → β and β → γ phase transitions at 2.71 GPa and 7.45 GPa. The significant changes of hydrogen bonding are indicated by the softened Raman modes, suggesting that the α → β phase transition may be a molecular layering reorganization process. The retrieved Raman and FT-IR spectra demonstrate that pressure-induced phase transitions are reversible upon decompression from 10 GPa to ambient pressure.