A solid state analysis of Metformin Picrate salt

Abstract The title compound Metformin picrate (3-diaminomethylidene-1,1-dimethylgunidine picrate) has been synthesized, crystallized and characterized using FT-IR, 1H-NMR, 13C-NMR and confirmed by using single crystal X-ray diffraction method. In addition, the intermolecular interactions in the crystal structure are analyzed using Hirshfeld surfaces computational method. The title compound crystallizes in a monoclinic crystal system of space group P21/c with cell parameters a = 11.4765(14) A, b= 5.6439 (7) A, c=24.213(3) A, β=94.286(7) A, V=1563.9(3) A3 and Z=4. An intermolecular interaction of the type N4-H4A...O7, N4-H4B...O2, N5-H5A...O6, N5-H5A...O7, N5-H5B...N6, N7-H7A...O1, N7-H7B...07 and C9-H9C...O4 connects the molecules of the crystal structure. The intermolecular interactions are responsible for crystal packing and are analyzed using Hirshfeld surface analysis, 2D finger print plots and molecular electrostatic potential surfaces. The inter contact O...H (52.1%) contributes more to the Hirshfeld surfaces for the title molecule. The crystal structure discloses the proton transfer from the phenolic group of picric acid to the amine group of metformin leading to the salt formation. The thermogravimetric analysis (TGA and DTA) measurement provided the thermal degradation of the Metformin picrate to be from 200 C. In addition the theoretical optimization was performed using density functional theory calculations to explore the physical and chemical properties of the electronic structure of the investigated compound.