Network Formation of Bis(2-benzimidazylmethyl)amine in Salts with Carboxylic Acids: The Structures Based on the Interplay of Strong and Weak Intermolecular Interactions

Abstract

Six new organic salts containing flexible and polydentate bis(2-benzimidazylmethyl)amine (BBMA) and a variety of carboxylic acids, including benzoic acid (HBA), p-nitrobenzoic acid (4-NHBA), 3,5-dinitrobenzoic acid (3,5-DiNHBA), terephthalic acid (H2TPA), trimesic acid (H3TMA), and pyromellitic acid (H4PMA), formulated as (HBBMA)·(HBA)·(BA) (1), (HBBMA)·(4-NBA)·(4-NHBA) (2), (H2BBMA)·(3,5-DiNBA)2 (3), (H2BBMA)·(TPA)·(H2TPA)0.5·DMF (4), (H2BBMA)·(H2TMA)2·DMF (5), and (H2BBMA)·(H2PMA) (6), have been synthesized. The salts were characterized by elemental analysis, IR, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction, to understand how variations in their molecular structures and intermolecular interactions influence their supramolecular assemblies. Proton transfer from the COOH to benzimidazole N acceptor (BimN) occurred in the six organic salts (1–6), leading to the ionic heterosynthon VI in all structures. Competition and cooperation between COOH, COO–, BimNH+, BimN, -NH2+-, and -NH- functional groups for the observed hydrogen bond synthons are examined in the six structures. To the best of our knowledge, there are no systematic studies on hydrogen bond competition and interplay when the above six H-bonded donors or acceptors are present in the same crystal structure. It is noted that C–H···O hydrogen bonds increase the dimensionality of the supramolecular architectures of the six salts (from one-dimensional (1-D) to two-dimensional (2-D) in 1; from 1-D to three-dimensional (3-D) in 2, from zero-dimensional (0-D) to 3-D in 3, from 2-D to 3-D in 5, from 1-D to 2-D in 6).