High-pressure-induced phase transition in 2-amino-6-nitrobenzothiazole

In situ high-pressure synchrotron angular dispersive x-ray diffraction (ADXRD) experiments reveal a pressure-induced structural phase transition in the molecular crystal of 2-amino-6-nitrobenzothiazole (C7H5N3O2S, 2A6NBT) at ∼2.0 GPa. Furthermore, in situ high-pressure Fourier transform-infrared absorption and Raman spectroscopy experiments confirm the occurrence of this phase transition and clarify the structural evolution. The N-H⋯N and C-H⋯O hydrogen bonds (along the c-axis direction), as well as the N-H⋯O hydrogen bonds (along the b-axis direction) and van der Waals force, are enhanced due to interlayer compression. When the pressure reaches about 2.0 GPa, the collapse of the molecular layer space and the distortion of the N-H⋯N hydrogen bond make the hydrogen-bonding network rearrange, leading to the phase transition. Finally, the evolution of molecular stacking is further illustrated by first principles calculations. This study provides important insights for the development of new supramolecular polymorphism containing various types of hydrogen-bonded interactions.