Thermal, structural, and conformational study of the benzimidazolone molecule

Good quality single crystals of benzimidazolone (C7H6N2O) were grown by slow evaporation of a solution at room temperature. The structure of the compound was determined by single-crystal X-ray diffraction. The compound was found to crystallize in monoclinic space group P21/n with Z = 4; the molecule is symmetrical to the mirror. The unit cell dimensions are: a = 5.20903(1) Å, b = 5.0557(1) Å, c = 23.4320(3) Å, and V = 627.26(5) Å3. The bicyclic system adopts a planar conformation and an intermolecular hydrogen bond is formed between the NH group and the oxygen atom of a neighbouring molecule. Thermal analysis was used to study heat transfer through the structure and Fourier transform infrared (FTIR) and polarized Raman spectral analysis were used to confirm the presence of compound’s functional groups. The experimental results were compared with those obtained theoretically by calculation, for example by use of the 3-21G* ab-initio method.