4-(4-Nitrobenzenesulfonamido)pyridinium trifluoroacetate

In the title compound, C11H10N3O4S+·C2F3O2 −, the benzene ring makes an angle of 87.3 (2)° with the pyridinium ring. The nitro group is essentially coplanar with the benzene ring. The F atoms of the CF3 group are disordered over two positions with almost equal occupancy [0.531 (12)/0.469 (12)]. The crystal structure is stabilized by N—H⋯O and C—H⋯O hydrogen bonds.

In the title compound, C 11 H 10 N 3 O 4 S + ÁC 2 F 3 O 2 À , the benzene ring makes an angle of 87.3 (2) with the pyridinium ring. The nitro group is essentially coplanar with the benzene ring. The F atoms of the CF 3 group are disordered over two positions with almost equal occupancy [0.531 (12)/0.469 (12)]. The crystal structure is stabilized by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds.

Comment
Organic pyridinium salts have been widely used in the construction of supramolecular architectures. As part of our ongoing studies of supramolecular chemistry involving the pyridinium rings (Li et al., 2007), the structure of the title compound was determined by X-ray diffraction.
In the cations of the title compound the short C-N distance is indicative of the slight conjugation of the sulphonamide N with the pyridinium ring. The benzene ring forms an angle of 87.3 (2)° with the pyridinium ring. The nitro group is essentially coplanar with the benzene ring The crystal packing is stabilized by N-H···O and C-H···O hydrogen bonds. (2007). Crystals were obtained by evaporation of a trifluoroacetic acid solution of the amide.

Refinement
The N-bound H atoms were located in a difference map and their coordinates were refined. The C-bound H atoms were positioned geometrically (C-H = 0.93 Å) and refined as riding atoms. The constraint U iso (H) = 1.2 U eq (C and N) was applied. The N1-H1A distance was restrained at 0.90 (1) Å and C-F distances to 1.36 (1) Å. The instruction ISOR (tolerance 0.01) was applied to restrain the displacement ellipsoids of all F atoms to an isotropic bahaviour. The CF 3 group was disordered with the occupancy of 0.531 (12):0.469 (12). Fig. 1. A view of the title compound with displacement ellipsoids drawn at the 50% probability level (arbitrary spheres for the H atoms). The dashed line indicates a hydrogen bond. Only the major component of the disordered CF 3 group is shown.

Special details
Geometry. All e.s. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-supplementary materials sup-3 factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.