4-Amino-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide–1,4-diazabicyclo[2.2.2]octane (2/1)

The asymmetric unit of the title co-crystal, C12H14N4O2S·0.5C6H12N2, comprises the sulfonamide molecule and half a molecule of 1,4-diazabicyclo[2.2.2]octane (DABCO), the latter being disposed about a crystallographic twofold rotation axis. In the sulfonamide molecule, the aromatic rings are almost perpendicular to one another [dihedral angle = 75.01 (8)°]. In the crystal, molecules are connected into a three-molecule aggregate via amide–DABCO N—H⋯N hydrogen bonds, and these are connected into a three-dimensional architecture via amino–DABCO N—H⋯O and amino-pyrimidine N—H⋯N hydrogen bonds.

The asymmetric unit of the title co-crystal, C 12 H 14 N 4 O 2 SÁ-0.5C 6 H 12 N 2 , comprises the sulfonamide molecule and half a molecule of 1,4-diazabicyclo[2.2.2]octane (DABCO), the latter being disposed about a crystallographic twofold rotation axis. In the sulfonamide molecule, the aromatic rings are almost perpendicular to one another [dihedral angle = 75.01 (8) ]. In the crystal, molecules are connected into a three-molecule aggregate via amide-DABCO N-HÁ Á ÁN hydrogen bonds, and these are connected into a threedimensional architecture via amino-DABCO N-HÁ Á ÁO and amino-pyrimidine N-HÁ Á ÁN hydrogen bonds.

Comment
The title co-crystal was formed in continuation of on-going structural studies of co-crystals (Ellis et al., 2009;Arman & Tiekink, 2013). While co-crystals of the title sulfonamide with carboxylic acids are known (Arman, et al. 2010;Ghosh et al. 2011;Smith & Wermuth, 2013), the present investigation appears to be the first describing a co-crystal of the sulfonamide with an amine.
The asymmetric unit of the title compound contains a molecule of the sulfonamide in a general position, and half a molecule of 1,4-diazabicyclo[2.2.2]octane (DABCO) which is disposed about a crystallographic two-fold rotation axis, Fig. 1. The overall shape of the sulfonamide approximates the letter L with the dihedral angle between the two aromatic rings being 75.01 (8)°, which compares to 78.1 (6)° found in the parent sulfonamide compound (Tiwari et al., 1984).
However, this is a little misleading as there is a difference in the conformation of the two sulfonamides. In the title sulfonamide the SOC 6 H 4 NH 2 residue lies to one side of the pyrimidinyl ring with the remaining O atom, O2, being coplanar giving the L-shape, whereas in the parent sulfonamide (Tiwari et al., 1984) the SO 2 O atoms lie to one side of the pyrimidinyl ring and the C 6 H 4 NH 2 residue to the other.
A three-dimensional architecture is formed in the crystal structure by N-H···O and N-H···N hydrogen bonds ( Fig. 2 and Table 1). The amide group, N1-H1N, forms a hydrogen bond to a DABCO N atom, N5, so that a three-molecule aggregate results. The amino group H atom, N4-H2N, is bifurcated, forming hydrogen bonds to the sulfonamide atom O2 and to the pyrimidinyl atom N2. The second amino group H atom, N4-H3N, forms a hydrogen bond to the second sulfonamide O atom, O1.

Refinement
The N-bound H-atoms were located in a difference Fourier map and refined with a distance restraint: N-H = 0.88 (1) Å with U iso (H) = 1.2U eq (N). The C-bound H-atoms were placed in calculated positions and included in the refinement in the riding model approximation: C-H = 0.95-0.99 Å with U iso (H) = 1.5U eq (C-methyl) and = 1.2 U eq (C) for other H atoms.    Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. 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 > 2σ(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.