Crystal structure of 1H-benzimidazole-2-carboxylic acid monohydrate_Kain Industrial Additive

Background and overview^[1]

1H-benzimidazole-2-carboxylic acid crystallizes as a monohydrate and exists in the form of a zwitterion, that is, 1H-benzimidazole-2-carboxylate. In the two-dimensional network, hydrogen bonds connect the acid and water. Molecules connect. 1H-benzimidazole-2-carboxylic acid, a simple carboxylic acid first synthesized by Bistrzycki and Przeworski (1912), has not found any important applications until now. Recently, it has been noted that its doubly deprotonated form may be an important ligand for the formation of polymeric transition metal complexes. Despite this, reports on its use in coordination chemistry are very scarce. In the reaction of 2-(oxazolin-2-yl)benzimidazole and CuCl₂, Cu^II complex and 1-H-benzimidazole-2- Carboxylate ligands, the unexpected acquisition of bis[(2-chloro)-(1H-benzimidazole-2-carboxy)dimethylformamide copper(II)] attracted attention . It is evident from its crystal structure that, as a monoanion, the acid can form transition metal complexes that enter the polymer band through NHO hydrogen bonding, and that these complexes may be polymer complexes formed from divalent anions. Analogs of compounds (Figure 1).

Crystal structure ^[2]

The asymmetric unit of 1H-benzimidazole-2-carboxylic acid monohydrate is shown in Figure 2. The atoms of the benzimidazole group are protonated and a zwitterionic form exists. In addition, it is confirmed that the N1-C2 and C2-N3 bond lengths of the imidazolium fragment are the same length, and the bond lengths of the carboxylate C10-O1 and C10-O2 are the same length. The molecule is approximately planar, with a dihedral angle of 5.0 (2) between the benzimidazole and the carboxylate. Hydrogen bonds connect the constituent molecules into a two-dimensional network (Figure 3).

Figure 2. The molecular structure of (I), with 50% probability displacement ellipsoids. The dashed line indicates a hydrogen bond.

Fig 3. The crystal structure of (I). (a) The crystal packing viewed along the a axis (b) The two-dimensional network of hydrogen-bonded dashbed lines) molecules.

Main reference materials

[1] Sławomir Krawczyk, Gdaniec M, Franciszek Sa˛czewski. 1H-Benzimidazole-2-carboxylic acid monohydrate[J]. Acta Crystallographica, 2005, 61(12):o4185-o4187.