Weak hydrogen bonds in bis(3-nitroanilinium) hexachloridostannate monohydrate. X-ray, vibrational and theoretical studies.

Crystal structures of bis(3-nitroanilinium) hexachloridostannate monohydrate, (H3NA)2SnCl6·H2O, was determined by means of X-ray single crystal diffraction. Relaxed potential energy surface of the H3NA(+) ion was calculated at the B3LYP/6-31(d,p) level. The energy of the H3NA(+) ion is approximately independent upon rotation of the ammonio group. It significantly depends on relative position of the nitro group towards aromatic ring. Theoretical spectra were calculated for the [(A-H3NA)Cl5·H2O](4-) and [(B-H3NA)Cl5](4-) anions, and thus hydrogen bonds of the ammonio group with the nearest neighboring atoms were included. PED results revealed that no coupling among all of the N-H oscillators exists. They vibrate separately because each hydrogen atom of the ammonio group of A- and B-H3NA(+) ions has different surroundings of the acceptors. Overall, very good agreement between theoretical and experimental frequencies was achieved.