Pressure- and Temperature-Induced Phase Transitions in 2,4,6-Trichloro-1,3,5-triazine Crystal.

The effects of pressure and temperature on the frequencies and band structures of the Raman active inter- and intramolecular vibrations of 2,4,6-trichloro-1,3,5-triazine crystal were studied. The changes in the Raman frequency, band width, and band structure of both the inter- and intramolecular vibrations induced by changes of pressure and temperature indicate that (1) a displacive phase transition caused by a shear distortion of π-stacked layer structure may take place under about 1.7 GPa at 298 K and (2) the intermolecular nitrogen–chlorine donor–acceptor attractive interactions supporting the extensive network structure in crystal have a direct effect upon the totally symmetric C–Cl stretching vibration.