Acta Cryst. (2009). E65, o98-o99  [ doi:10.1107/S1600536808041214 ]

4-[(5-Bromo-2-hydroxybenzylidene)amino]-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide-4-bromo-2-[(E)-({4-[(4,6-dimethylpyrimidin-2-yl)sulfamoyl]phenyl}iminio)methyl]phenolate [0.61 (7)/0.39 (7)]

H. A. Shad, M. N. Tahir and Z. H. Chohan

Abstract: The title compound, 0.61C₁₉H₁₇BrN₄O₃S·0.39C₁₉H₁₇BrN₄O₃S, is a Schiff base derived from 5-bromosalicylaldehyde and 4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzenesulfonamide(sulfamethazine) and is isostructural with its chloro analogue. The geometry of the title molecule points to the enol (OH-C=C-C=N) form as the major tautomer, however two electron-density maxima corresponding to the H atoms of the OH and NH groups, found in the region of a strong intramolecular NHO hydrogen bond, do not allow the elimination of the presence of the zwitterionic (O^--C=C-C=NH⁺) form in the crystal. Refinement of the occupancies of these H atoms gave a 0.61 (7):0.39 (7) ratio of the enolic and zwitterionic forms. The two benzene rings within the molecule are nearly coplanar and the central benzene ring forms a dihedral angle of 84.1 (1)° with the pyrimidine fragment. An intermolecular N-HO hydrogen bond links molecules into chains extended along the a axis and a C-HO link is also present. The H atoms of one of the methyl groups are disordered over two sites with an occupancy ratio of 0.72 (7):0.28 (7).

Online 13 December 2008

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