2-(Benzenesulfonamido)pyridinium perchlorate

In the title compound, C11H11N2O2S+·ClO4 −, the dihedral angle between the benzene and pyridinium rings is 87.33 (10)°. An intramolecular N—H⋯O interaction, with an S=O-bonded O atom as receptor, occurs in the cation. In the crystal structure, ion pairs occur, being linked by strong N—H⋯O hydrogen bonds. The perchlorate anion plays a further role in the molecular packing by accepting several weak C—H⋯O interactions.

In the title compound, C 11 H 11 N 2 O 2 S + ÁClO 4 À , the dihedral angle between the benzene and pyridinium rings is 87.33 (10) . An intramolecular N-HÁ Á ÁO interaction, with an S Obonded O atom as receptor, occurs in the cation. In the crystal structure, ion pairs occur, being linked by strong N-HÁ Á ÁO hydrogen bonds. The perchlorate anion plays a further role in the molecular packing by accepting several weak C-HÁ Á ÁO interactions.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB2972).

Comment
Organic pyridinium salts have been used as not only supramolecular guests (Li et al., 2007;Li, Fan, Fan et al., 2008), but also catalysts and/or media for esterification (Ganeshpure et al.2007;Miyashita et al. 1977). To seek a new pyridinium catalyst for biodiesel transformation, the title compound, (I), was synthesized and further determined by X-ray diffraction.
The title compound, (I), consists of a pyridinium cation and a perchlorate anion (Fig. 1). In the cation, the distance [1.383 (2) Å] between the pyridinum C atom and its connected amino N atom is slightly longer than the nitrate [1.378 (2) Å] (Li et al. 2009), also showing some conjugation of amino group with pyridinium ring. The benzene ring constructs an angle of 87.33 (10)° with the pyridinium ring, similar to the nitrate [87.59 (8)°]. The cation structure is stabilized by an intramolecular N-H···O hydrogen bond (Table 1), with S=O oxygen as H-bonding receptor, different from by C-H···O interaction in the nitrate.
Like the nitrate, in the crystal structure, a strong N-H···O hydrogen bond link the cation and anion (Table 1). The anion ClO 4 plays a great important role in the molecular packing via weak C-H···O interactions (Table 1).

Experimental
The title compound was prepared according to the reported literature (Li, Yang et al. 2008). Colourless needles of (I) were obtained by evaporation of a perchloric acid solution of the sulfonamide.

Refinement
The H atoms bound to C were positioned geometrically (C-H = 0.95 Å)and refined as riding with U iso (H) = 1.2 U eq (C)].