Crystal Structure Analysis and Topological Study of Non-covalent Interactions in 2,2-Biimidazole:Salicylic Acid 2:1 Co-crystal

Abstract

The 1:2 ratio salicylic acid/biimidazole co-crystal is studied in this work. I This compound was obtained from a flux with methanol followed by slow evaporation, rendering colorless plates, that crystallize in the monoclinic system, space group P21/n, with unit cell parameters a = 12.0969 (4) A, b = 5.0714 (1) A and c = 15.4825 (4) A, β = 99.007(2)o, and V = 938.11(4) A3. The experimental characterization is achieved through X-ray diffraction structure analyzes, infrared spectroscopy (FTIR) and thermal analysis (TGA/DSC). This characterization is complemented by theoretical calculations at the DFT/6–31++G(d,p) level, employing the HCTH407 functional. Geometrical optimizations are performed and a detailed Non-Covalent-Index analysis is carried out. It is found that the crystal structure is maintained by conventional and non-conventional hydrogen bonds, of the type N–H···O, O–H···N and C–H···O hydrogen bonds responsible for the formation of planar supramolecular units forming R2 2(9) rings and slip-stacked packing, which, through DFT/HCTH calculations, are shown to stabilize the structure. The synthesis and crystal structure of the title compound, C10H9N2O3, is reported. The bimidazole and salicylic acid form a co-crystal in a 1:2 ratio. Its crystal structure is maintained by conventional and non-conventional hydrogen bonds. Two conventional hydrogen bonds, of the type N–H···O and O–H···N, form planar supramolecular unit through R2 2(9) rings, the DFT/HCTH calculations shows us that the R2 2(9) rings formation stabilize the supramolecular structure.