Synthesis and characterization of two organic cation hydrogensulfates: 1-(2,5-dimethylphenyl)piperazine-1,4-diium bis(hydrogensulfate) monohydrate (SI) and 1-(2,3-dimethylphenyl)piperazine-1,4-diium bis(hydrogensulfate) (SII).

Treatment of 1-(2,5-dimethylphenyl)piperazine and 1-(2,3-dimethylphenyl)piperazine with H 2 SO 4 in 2:1 molar ratio at RT affords the corresponding sulfate salts [C 12 H 20 N 2 ][HSO 4 ] 2 ·H 2 O (SI) and [C 12 H 20 N 2 ][HSO 4 ] 2 (SII). These compounds have been characterized by X-ray diffraction, thermal analysis and spectroscopic investigations (IR and NMR). In the atomic arrangement of (SI) the HSO 4 − anions are associated by pairs linked to the water molecules forming corrugated ribbons, while in the (SII) structure, the pairs of the HSO 4 − anions form corrugated chains. Solid-state 13 C and 15 N CP-MAS NMR spectroscopies are in agreement with the X-ray structure. The vibrational absorption bands were identified by infrared spectroscopy. NMR peaks were attributed with the aid of DFT calculations. The electronic properties such as HOMO and LUMO energies were determined. [ABSTRACT FROM AUTHOR]