2-[(2-Carboxyphenyl)disulfanyl]benzoic acid–4,4′-bipyridyl N,N′-dioxide (1/2)

In the title 2:1 adduct, C14H10O4S2·0.5C10H8N2O2, which arose from an unexpected oxidation of a precursor, the dihedral angle between the aromatic rings in the disulfide is 82.51 (11)°. In the crystal, the molecules are linked by O—H⋯O, O—H⋯N and C—H⋯O interactions, generating sheets.

In the title 2:1 adduct, C 14 H 10 O 4 S 2 Á0.5C 10 H 8 N 2 O 2 , which arose from an unexpected oxidation of a precursor, the dihedral angle between the aromatic rings in the disulfide is 82.51 (11) . In the crystal, the molecules are linked by O-HÁ Á ÁO, O-HÁ Á ÁN and C-HÁ Á ÁO interactions, generating sheets.

Experimental
The sinthesis of the title compound (I) was carried out by slow evaporation of equimolar quantities of 2-mercaptobenzoic acid (0.537 g., 0.0035 mol) and 4,4'-bipyridyl N,N'-dioxide (0.655 g) in 50 ml of dry acetonitrile. Pale-yellow prisms of good quality, suitable for X-ray analysis were obtained. The initial reagents were purchased from Aldrich Chemical Co. and were used as received.
supplementary materials sup-2 Refinement All H-atoms were located from difference maps and were positioned geometrically and refined using a riding model with C-H= 0.93-0.97 Å and Uiso(H)= 1.2U eq (C). Fig. 1. An ORTEP-3 (Farrugia, 1997) plot of the title (I) compound, with the atomic labelling scheme. The shapes of the ellipsoids correspond to 50% probability contours of atomic displacement and, for the sake of clarity, H atoms are shown as spheres of arbitrary radius.

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.
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.