2-(Ammoniummethyl) pyridinium dihydrogen squarate hydrate: An experimental and theoretical study

• IR–UV spectroscopy and X-ray single crystal diffraction.
• Squaric acid, Ab initio calculations.
• CAHB interactions are dominant in the crystal packing.
• This research is investigation of supramolecular architectures of title structures.

The experimental and theoretical investigation results of newly synthesized squarate salt of 2-(ammoniummethyl) pyridinium dihydrogen squarate hydrate (1), 2(C4HO4)·C6H10N2·H2O, were reported in this study. The crystal structure of the title compound was found to crystallize in the triclinic P–1   space group. Each of two squaric acid molecule in the asymmetric unit has donated one H atom to the nitrogen atom of pyridine part and one to the nitrogen atom of methyl part of a 2-(aminomethyl) pyridine molecule, forming the (1) salt. The X-ray analysis clearly indicated that the crystal packing has shown the hydrogen bonding ring pattern of R34(14) through OH⋯O and NH⋯O together with R24(14) pattern through NH⋯O interactions. Ab initio calculations were performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/ 6-31++G(d,p) (3) level of theory. The results of the optimized molecular structure and vibrational properties for the 1 obtained on the basis of two models are presented and compared with the experimental data. The molecular electrostatic potential (MEP), frontier molecular orbitals (FMOs) and conformational flexibility of the title compound were also studied at the 2 level.