Structure of six anhydrous molecular salts assembled from noncovalent associations between carboxylic acids and bis-N-imidazoles

Abstract

Six crystalline organic acid–base adducts derived from bis(N-imidazolyl) and carboxylic acids (3,5-dinitrobenzoic acid, 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid, and phthalic acid) were prepared and characterized by X-ray diffraction analysis, IR, mp, and elemental analysis. The six compounds are all organic salts. In salts 1, 2, 4, 5, and 6 the corresponding bis(imidazole) derivatives are diprotonated, while in 3, the corresponding bis(imidazole) derivative is only monoprotonated.All supramolecular architectures of the salts 1–6 involve extensive NH⋯O, OH⋯O, CH⋯O, and CH2⋯O hydrogen bonds as well as other noncovalent interactions. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. All the salts displayed 3D framework structures under the cooperation of these weak interactions.The results presented herein indicate that the strength and directionality of the N+H⋯O−, OH⋯O, and NH⋯N hydrogen bonds between carboxylic acids and ditopic imidazoles are sufficient to bring about the formation of binary organic salts.