4-[(3-Formyl-4-hydroxyphenyl)diazenyl]-N-(pyrimidin-2-yl)benzenesulfonamide

The title molecule, C17H13N5O4S, has a trans configuration with respect to the diazenyl (azo) group. The pyrimidine ring and the terminal benzene ring are inclined at angles of 89.38 (4) and 1.6 (6)°, respectively, with respect to the central benzene ring. The conformation of the molecule is in part stabilized by an intramolecular O—H⋯O hydrogen bond. In the crystal structure, molecules related through inversion centers form hydrogen-bonded dimers involving the sulfonamide N—H group and the N atom of the pyrimidine ring.

The title molecule, C 17 H 13 N 5 O 4 S, has a trans configuration with respect to the diazenyl (azo) group. The pyrimidine ring and the terminal benzene ring are inclined at angles of 89.38 (4) and 1.6 (6) , respectively, with respect to the central benzene ring. The conformation of the molecule is in part stabilized by an intramolecular O-HÁ Á ÁO hydrogen bond. In the crystal structure, molecules related through inversion centers form hydrogen-bonded dimers involving the sulfonamide N-H group and the N atom of the pyrimidine ring. 245 parameters H-atom parameters constrained Á max = 0.42 e Å À3 Á min = À0.37 e Å À3 Table 1 Hydrogen-bond geometry (Å , ).

4-[(3-Formyl-4-hydroxyphenyl)diazenyl]-N-(pyrimidin-2-yl)benzenesulfonamide
H. El-Ghamry, R. Issa, K. El-Baradie, K. Isagai, S. Masaoka and K. Sakai Comment Sulfa-drugs are widely used in the treatment of infections, especially for patients intolerant to antibiotics (Nagaraja et al., 2002). The vast commercial success of these medical agents has made the chemistry of sulfonamides become a major area of research and an important branch of commercial importance in pharmaceutical sciences (Nagaraja et al., 2002). Heterocyclic azo compounds are also considered very important class of compounds. The importance of these compounds may stem from its biological activity and analytical investigations (Gaber et al., 2008). Also, it is well known that heterocyclic azo compounds have been used to establish the low oxidation states of different metal ions (Kakoti et al., 1993;Santra & Lahiri, 1997;Misra et al., 1998). What appears more important is that sulfonamide and azo-sulfonamide derivatives have been found to be biologically versatile anticancer (La Roche & Co, 1967a,b) and antitubercular (Vaichulis, 1977) drugs.
In the title compound (I), C 17 H 13 N 5 O 4 S, the two aromatic groups attached to the azo double bond are oriented in a trans fashion. All the bond lengths are found to be within the normal values (Allen et al., 1987). An intramolecular hydrogen bond is formed between the O-H (hydroxyl) group and the oxygen atom of the carbonyl group (O2-H1···O1; Table   1), stabilizing the coformation of the molecule. Moreover, the molecule is further correlated with an adjacent molecule through an inversion center, where the intermolecular interaction is stabilized with two hydrogen bonds formed between the N-H(sulfonamide) group and the nitrogen atom of pyrimidine ring, N3-H···N5 i hydrogen bond [symmetry code: (i) 1 -x, 2 -y, 1 -z] (see Fig. 2 and Table 1). There is an unusually short intermolecular contact between the C (carbonyl) and the O (sulfonamide) atoms, i.e., C1···O3 ii = 2.91 (2) Å [symmetry code: (ii) 2 -x, 1/2 + y, 3/2 -z]. Although the rotation about the C10-S1 bond axis is essentially allowed, the rotation at this geometry is fixed as a result of strong intermolecular hydrogen bonds formed at the peripheral pyrimidine attached to the sulfonamide unit. This must be the major cause of the short contact found for one of the sulfonamide oxygen atoms, i.e., O3.
The pyrimidine ring and both the central and terminal benzene rings are found to have a planar geometry (r.m.s deviations are 0.0136, 0.0106 and 0.0225 Å, respectively). Both the pyrimidine and the terminal phenyl rings are canted with respect to the central phenyl ring at angle of 89.38 (4) and 1.6 (6)°, respectively. suitable for x-ray measurement was prepared by vapour diffusion method in which compound (I) was dissolved in the least possible amount of DMF and then the solution was left at room temperature in the presence of water pool outside. The outside water slowly diffused by vapour and gradually mixed with DMF of the dye. After 7 days, dark orange crystals suitable for X-ray diffraction analysis was separated out.

Refinement
All H atoms were placed in idealized positions, (C-H = 0.95 Å, O-H = 0.84 Å, and N-H = 0.88 Å), and included in the refinement in a riding-model approximation, with U iso (H) = 1.2Ueq (C and N) and U iso (H) = 1.5Ueq (O). In the final difference Fourier map, the highest peak was located 0.83 Å from atom C10. The deepest hole was located 0.64 Å from atom S1. Fig. 1. The molecular structure of (I) showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Special details
Experimental. The first 50 frames were rescanned at the end of data collection to evaluate any possible decay phenomenon. Since it was judged to be negligible, no decay correction was applied to the data. 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 Rfactors(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.