Sulfonamide Molecular Crystals: Thermodynamic and Structural Aspects

The crystal structures of three sulfonamides with the structures C6H5-SO2NH-C6H5, C6H5-SO2NH-C6H4-R (R = 4-NO2), 4-NH2-C6H4-SO2NH-C6H4-R (R = 4-NO2; 4-CN) have been determined by X-ray diffraction. On the basis of our previous data and the obtained results, comparative analysis of crystal properties was performed: molecular conformational states, packing architecture, and hydrogen bond networks using graph set notations. Conformational flexibility of the bridge connecting two phenyl rings was studied and described by a correlation equation. Hydrogen bonds were grouped according to the frequency of hydrogen bond appearance within the definite graph set assignment. The strength of the hydrogen bonds was evaluated. The influence of various molecular fragments on crystal lattice energy was analyzed. A correlation between melting points and fragmental molecular interactions in the crystal lattices was obtained. The thermodynamic aspects of the sulfonamide sublimation were studied by investigating the temperature dependence of vapor pressure using the transpiration method. A correlation between the Gibbs energy of the sublimation process and molecular H-bond acceptor factors was found. In addition, a regression equation was derived for describing the correlation between the sublimation entropy terms and crystal density data calculated from X-ray diffraction results. These dependencies allow us to predict sublimation thermodynamic parameters not knowing more than the molecular formula and crystal density.