X-ray, vibrational and theoretical studies of weak hydrogen bonds in bis(4-nitroanilinium) hexachloridostannate.

Crystal structure of bis(4-nitroanilinium) hexachloridostannate, (H4NA)2SnCl6, was determined by means of X-ray single crystal diffraction. In the crystal structure, weak N-H…Cl hydrogen bonds are present. These interactions were taken into consideration in calculations of vibrational spectra for the (H4NA)Cl4O anion. Very good agreement between theoretical and experimental frequencies was achieved. The calculations were done at the B3LYP/6-311+G(2d,1p) level including Grimme's correction for dispersion. The relaxed potential energy surface indicated that the energy of H4NA(+) ion is approximately independent upon rotation of the ammonio group. The energy barrier is 0.01 kcal/mol. Therefore the position of the ammonio group can be easily modified the other interacting molecules during molecular self-assembly and crystal growth processes. The energy of the H4NA(+) ion significantly depends on the relative position of the nitro group towards the aromatic ring. The energy barrier of the nitro group is 4.35 kcal/mol.