4-(4-Nitrobenzenesulfonamido)pyridinium trichloroacetate

In the title compound, C11H10N3O4S+·C2Cl3O2 −, the benzene ring forms an angle of 85.21 (13)° with the pyridinium ring. The nitro group is nearly coplanar with its attached benzene ring [dihedral angle = 3.68 (12)°]. In the crystal structure, strong N—H⋯O hydrogen bonds link the ion-pairs. The packing is further consolidated by weak C—H⋯O interations.

In the title compound, C 11 H 10 N 3 O 4 S + ÁC 2 Cl 3 O 2 À , the benzene ring forms an angle of 85.21 (13) with the pyridinium ring. The nitro group is nearly coplanar with its attached benzene ring [dihedral angle = 3.68 (12) ]. In the crystal structure, strong N-HÁ Á ÁO hydrogen bonds link the ion-pairs. The packing is further consolidated by weak C-HÁ Á ÁO interations.

Related literature
For the synthesis and structure of the unprotonated amine, see: Yu & Li (2007). For reference geometrical data, see: Allen et al. (1987).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB2642).
The cation and anion are connected by a strong N-H···O hydrogen bond and weak C-H···O interactions (Table 1) complete the structure. Two short intramolecular C-H···O contacts also arise in the cation. Yu & Li (2007). Colourless blocks of (I) were grown by natural evaporation from a trichloroacetic acid solution of the amide.

S3. Refinement
The N-bound H atoms were located in a difference map and their positions were freely refined. The C-bound H atoms were positioned geometrically (C-H = 0.93 Å) and refined as riding atoms. The constraint Uĩso~(H) = 1.2 U~eq~(C and N) was applied.

Figure 1
A view of (I) with displacement ellipsoids drawn at the 50% probability level (arbitrary spheres for the H atoms).   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-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.