Crystal structures of isomeric 4-bromo-N-[(2-nitrophenyl)sulfonyl]benzamide and 4-bromo-N-[(4-nitrophenyl)sulfonyl]benzamide

The isomeric title compounds both display three-dimensional supramolecular architectures arising from N—H⋯O, C—H⋯O, C—H⋯π and π–π interactions.


Chemical context
In recent years, N-(arylsulfonyl)arylamides have received much attention as they constitute an important class of drugs for treating Alzheimer's disease (Hasegawa & Yamamoto, 2000) and acting as anti-bacterial inhibitors of tRNA synthetases (Banwell et al., 2000), antagonists for angiotensin II (Chang et al., 1994) and as leukotriene D4-receptors (Musser et al., 1990). Further, N-(arylsulfonyl)-arylamides are known to be potent anti-tumour agents against a broad spectrum of human tumour xenografts (colon, lung, breast, ovary and prostate) in mice (Mader et al., 2005). In a continuation of our work on the synthesis and crystal structures of N-(2-nitrophenylsulfonyl)arylamides (Suchetan et al., 2012a) and N-(4nitrophenylsulfonyl)arylamides (Suchetan et al., 2012b), compounds (I) and (II) were synthesized and their crystal structures determined.

Figure 1
A view of (IA), showing displacement ellipsoids drawn at the 50% probability level.

Figure 2
A view of (II), showing displacement ellipsoids drawn at the 50% probability level.

Synthesis and crystallization
Compounds (I) and (II) were prepared by refluxing a mixture of 4-bromobenzoic acid, the corresponding substituted benzenesulfonamide and phosphorus oxychloride for 3 h on a water bath. The resultant mixtures were cooled and poured into ice-cold water. The solids obtained were filtered, washed thoroughly with water and then dissolved in sodium bicarbonate solutions. The compounds were later reprecipitated by acidifying the filtered solutions with dilute HCl. They were filtered, dried and recrystallized. [m.p. = 486 for (I) and 498 K for (II)]. Colourless prisms of (I) and (II) were obtained by slow evaporation of the respective solutions of the compounds in methanol (with a few added drops of water).

Refinement details
Crystal data, data collection and structure refinement details are summarized in The crystal packing of (I), displaying the hetero R 2 2 (11) dimeric supramolecular synthon. Molecules assemble along the a axis forming C(6) chains via C-HÁ Á ÁO interactions while two further C-HÁ Á ÁO interactions involving the same acceptor atom lead to the formation of an R 2 1 (5) network.

Figure 4
Structure-directing C-HÁ Á ÁO interactions in the crystal structure of (II) propagating along the b axis as chains.

(I) 4-Bromo-N-[(2-nitrophenyl)sulfonyl]benzamide
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.002 Δρ max = 0.71 e Å −3 Δρ min = −1.11 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.002 Δρ max = 1.10 e Å −3 Δρ min = −1.69 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.