Experimental and Theoretical Evidence for Supramolecular Self-Assembly and Hydrogen Bonding between Squaric Acid and 2,6-Bis(2-benzimidazolyl)pyridine

Supramolecular complex (1) was obtained from a mixture of squaric acid and 2,6-bis(2-benzimidazolyl)pyridine in deuterated dimethylsulfoxide (d-DMSO) and characterized by single-crystal X-ray diffraction. The crystal structure data showed that 1 was a one-dimensional chain polymer assembled through pi-pi stacking and hydrogen bonding interactions. Infrared vibrational spectra of 1 were measured at different temperatures and sample concentrations in carbon tetrachloride. Moreover, the hydrogen bonding in the crystals was further evaluated by density functional theory (DFT) and atoms in molecules (AIM) theory. The calculated hydrogen bonding energies were about 135.65 and 49.40 J . mol(-1), respectively.