Covalent symmetrization of the hexagonal networks of trimesic acids at high pressure

The covalent symmetrization of the hexagonal networks of 1,3,5-trimesic acids under compression was studied applying inelastic Raman spectroscopic scattering in the pressure range 0–7.6 GPa. The first pressure induced phase transition, resulted from representative warping of trimesic acids network plane, was observed when compression met 0.4 GPa. Above approximately 1.9 GPa, as reflected in our Raman data, intra-plane hydrogen bonds became covalent and proton became homogeneous. Further compression beyond 7.6 GPa led to a significant loss of long-range order, marked by amorphization. Pressure-induced transformation and its mechanisms, exhibited in our experiment, reflect a characteristic structural transition of symmetric trimesic acids resulted from the effect of hydrogen-bonding interaction.