Importance of weak interactions in developing 1,3-bis(4,6-dimethyl-1H-nicotinonitrile-1-yl)1,3-dioxy propane polymorphs

The structure of 1,3-bis(4,6-dimethyl-1H-nicotinonitrile-1-yl)1,3-dioxy propane polymorphs has been characterized by X-ray diffraction, FT-IR, 1H and 13C NMR spectroscopies. The influence of intra and intermolecular weak interactions is thoroughly studied in solid state using single crystal X-ray diffraction and FT-IR. These polymorphs belong to monoclinic space group ‘P21/n’ and ‘P21/c’. These polymorphs have C–H⋯n (lone pair), hydrogen bonds, C–N⋯π, C–H⋯π and π⋯π intermolecular non-covalent interactions. These polymorphs are the result of weak interactions and solvent used in crystallization. The FT-IR spectra have been recorded in the solid phase and NMR has been recorded in solvent. The optimized geometry has been calculated by B3LYP methods using different basis sets. The FT-IR and NMR spectra of 1st polymorphs has been calculated at B3LYP/6–31G (d) level. The scaled theoretical wave number showed good agreement with the experimental values. These two polymorphs as well as other stereomers are studied by DFT calculations.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Polymorphism: These become important branch in pharmaceutical chemistry due to activity difference in polymorphs. ► Non-covalent interactions: These weak interactions play a vital role to develop polymorphism in compounds. ► Spectroscopy methods: Here these interactions have been studied via NMR, FT-IR and single crystal X-ray diffractions. ► Calculations: The calculations were performed using the Gaussian 03 package.