Novel 1,2,4-Thiadiazole Derivatives: Crystal Structure, Conformational Analysis, Hydrogen Bond Networks, Calculations, and Thermodynamic Characteristics of Crystal Lattices

The
results of X-ray crystallographic and computational studies
of twelve 1,2,4-thiadiazole derivatives are reported. The effect of
orientation of different parts of the molecules on crystal organization
and hydrogen bond network were studied. DFT calculations were carried
out in order to explore conformational preferences of the molecules
inside and outside of crystal environment. The role of hydrogen bonds
was found to be essential for the stabilization of conformationally
strained molecules as well as for the packing density of such molecules
in a crystal. Thermodynamic aspects of sublimation processes of the
studied compounds were analyzed using temperature dependencies of
their vapor pressure. Thermophysical characteristics of the molecular
crystals were obtained and compared with the sublimation enthalpy
and the structural parameters. The influence of crystal structure
features on the sublimation enthalpy and on the melting temperature
was analyzed.