Molecular arrangement planarization induces a high-pressure polymorphism transition of the hydrogen-bonded organic crystal maltol

Abstract

The high-pressure behavior of maltol (3-hydroxy-2-methyl-4H-pyran-4-one, C6H6O3) molecular crystals has been investigated using in situ high-pressure Raman spectroscopy and synchrotron angular dispersive x-ray diffraction. The results of the high-pressure experiments indicate that the transition from phase II (monoclinic, P21/c) to phase III (monoclinic, P21/c) occurs at pressures above 2.0 GPa and is completed at pressures above 6.4 GPa. The mechanism of the phase transition is that the fastest compression along the c-axis at high pressures leads to a planarization tendency of supramolecular layers, which triggers the rearrangement of O–H⋯O and C–H⋯O hydrogen bonds. This study provides a theoretical basis for the development of supramolecular materials with layered hydrogen-bonded networks.