Investigation of hydrogen bonding patterns in a series of multi-component molecular solids formed by tetrabromoterephthalic acid with selected N-heterocycles

Abstract

The supramolecular reactions of tetrabromoterephthalic acid (H₂-TBTA) with a series of N-heterocycles afforded eight new complexes, namely, [(H₂-BTAH)₂·(TBTA)·(H₂-TBTA)] (1), [(H₂-Bim)₂·(TBTA)·(H₂-TBTA)·2H₂O] (2), [(H-8-HQ)₂·(TBTA)·3H₂O] (3), [(5-NO₂-phen)₂·(H₂-TBTA)] (4), [(4,6-DHP)₂·(H₂-TBTA)·2H₂O] (5), [(H₂-2,4-DMI)₂·(TBTA)·(H₂-TBTA)₂] (6), [(H₂-3,5-DMP)₂·(TBTA)] (7), and [(H-4-CNpy)₂·(TBTA)·(H₂-TBTA)] (8) (H-BTAH = 1H-benzotriazole, H-Bim = 1H-benzimidazole, 8-HQ = 8-hydroxyquinoline, 5-NO₂-phen = 5-nitro-1,10-phenanthroline, 4,6-DHP = 4,6-dihydroxypyrimidine, H-2,4-DMI = 2,4-dimethylimidazole, H-3,5-DMP = 3,5-dimethylpyrazole, and 4-CNpy = 4-cyanopyridine), which have been prepared under mild and identical reaction conditions in a mixture of distilled water and ethanol. All the complexes were fully characterized using single crystal X-ray diffraction analysis, elemental analysis, infrared spectroscopy (IR), and thermogravimetric analysis (TGA). Combining the various N-containing ligands and the diversity of the hydrogen bonds, the eight crystals display amusing structural characteristics. Among these complexes, complex 3 forms a three-dimensional (3D) network through the C–H⋯Br bonds, while the O–H⋯Br bonds facilitate the 3D construction of compound 2. Complexes 4–8 generate 3D supramolecular structures by utilizing a large number of hydrogen bonds. In crystal 1, the π–π stacking interactions play an important part in the 3D network. The thermal stability of crystals 1–8 has been investigated by thermogravimetric analysis (TGA) of mass loss.