High-pressure studies on fluorine substituted 2,5-di(phenyl)-1,3,4-oxadiazoles

Results are presented from structural and high-pressure investigations on four differently but symmetrically fluorine substituted 2,5-di(phenyl)-1,3,4-oxadiazoles. The substitution pattern includes the para-, meta-, or ortho-substitution and the fully fluorinated 2,5-bis(pentafluorophenyl)-1,3,4-oxadiazole. The crystal structure depends on the molecular structure and results in a different high-pressure behavior. Parameters for the Murnaghan equation of state (EOS) are determined for every compound and the anisotropic pressure response of the crystal lattice is discussed. Although the EOS parameters, bulk modulus Ko and its pressure derivative Ko′ are of the same order of magnitude for all four compounds, the anisotropy of strain is noticeably different.