High pressure studies of Ni3[(C2H5N5)6(H2O)6](NO3)6 • 1.5H2O by Raman scattering, IR absorption, and synchrotron X-ray diffraction

Herein, we report the high-pressure studies of Ni-3[(C2H5N5)(6)(H2O)(6)](NO3)(6) center dot 1.5H(2)O (1) by in situ Raman scattering, infrared absorption, and synchrotron angle-dispersive X-ray diffraction techniques up to similar to 22 GPa at room temperature. We assigned all the vibration modes of 1 at ambient conditions. Detailed spectroscopy analyses revealed a chemical transformation at similar to 0.75 GPa and a phase transition at similar to 4.7 GPa, which are related to the behaviors of energetic ligands and flexible structures. Upon compression, the distortion of the energetic ligand induced the disconnection of NH2 and the triazole ring at 0.75 GPa. Further analyses of the N-H vibration modes indicated the phase transition at 4.7 GPa accompanied with the rearrangement of hydrogen bonds. In addition, the lattice structure abnormally expanded above 8.6 GPa due to the deformation of nitrate ions and the extension of the triazole ring. This study helps to understand the properties and the behavior of energetic coordination complexes under high pressure.