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)]

The title compound, 0.61C(19)H(17)BrN(4)O(3)S·0.39C(19)H(17)BrN(4)O(3)S, is a Schiff base derived from 5-bromo-salicylaldehyde and 4-amino-N-(4,6-dimethyl-2-pyrimidin-yl)benzene-sulfonamide(sulfamethazine) and is isostructural with its chloro analogue. The geometry of the title mol-ecule 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 intra-molecular N⋯H⋯O 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 mol-ecule are nearly coplanar and the central benzene ring forms a dihedral angle of 84.1 (1)° with the pyrimidine fragment. An inter-molecular N-H⋯O hydrogen bond links mol-ecules into chains extended along the a axis and a C-H⋯O 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).