Gallic acid-butyramide monohydrate cocrystal: Crystal growth, Structural insights, Theoretical calculations and Molecular docking studies against COVID-19 main protease

Single crystal X-ray diffraction is the only experimental technique available to elucidate the complete three-dimensional structure of the samples at molecular and atomic levels. But this technique demands defect-free single crystals. Growing good quality single crystals which are suitable to collect X-ray intensity data is an art rather than science. Among the various crystal growth methods, the most effective and commonly used is the slow evaporation method. Using this method, defect-free single crystals of the ground mixture of gallic acid (GA) and butyramide (BU) taken in a 1:1 molar ratio are obtained. The compound was subjected to experimental characterizations like; PXRD, FTIR, SCXRD, and TGA. Further, these results were utilized in the computational characterizations namely, Hirshfeld surface analysis, interaction energy calculations, DFT studies, and docking studies. Structural characterization revealed that the GA-BU compound was crystallized as a cocrystal hydrate with 2:1:1 stoichiometry in a monoclinic crystal system and P21/n space group. Structural studies exposed the presence of various inter and intramolecular hydrogen bond interactions, ring synthons, DDAA environment of the water molecule, and π ... π stacking interactions. The contribution of the several close contacts to the crystal structure, the influence of different interaction energies in the packing, the HOMO-LUMO energy gap, and the location of reactive sites were realized through computational studies. Further, a molecular docking study has been performed to check the antiviral activity of the title compound against COVID-19.