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

Abstract

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 'P2(1/n)' and 'P2(1/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.