Structural elucidation, theoretical insights and thermal properties of three novel multicomponent molecular forms of gallic acid with hydroxypyridines

Abstract

Development of novel drug for manipulating the physicochemical properties of the API by obtaining their multicomponent forms is a challenging task in the pharmaceutical industry. Novel multicomponent crystal forms of gallic acid with three hydroxypyridines have been prepared by liquid assisted grinding and slow evaporation of the solvent. Preliminary PXRD and FTIR characterizations were carried out to confirm the interactions between the components, then the three dimensional molecular structures were confirmed through single crystal X-ray diffraction method. Structural studies clearly revealed the three distinct molecular crystal forms of gallic acid with hydroxypyridines. The molecular structures exhibit O–H⋯O, N–H⋯O and C–H⋯O intermolecular hydrogen bond interactions, which results different supramolecular motifs. Further, intermolecular interactions were quantified through Hirshfeld surface analysis, which revealed the dominance of O⋯H and H⋯H interactions. Computation of interaction energies between the molecules and analysis of three dimensional energy frameworks quantifies the molecular packing. The density functional theory calculations were employed to optimize the structural coordinates, which substantiate the experimental results. Low value of HOMO-LUMO energy gap signifies the promising electronic properties of the molecules. The chemical reactive sites were further identified on the molecular electrostatic potential surface. Finally, thermal properties of the crystals were studied using thermogravimetric analysis.