4-(2-Hydroxyphenyl)-3,5-dithiaheptanedioic acid

In the crystal of the title compound, C11H12O5S2, molecules are linked by O—H⋯O hydrogen bonds and C—H⋯O interactions, forming a three-dimensional network.

In the crystal of the title compound, C 11 H 12 O 5 S 2 , molecules are linked by O-HÁ Á ÁO hydrogen bonds and C-HÁ Á ÁO interactions, forming a three-dimensional network.
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009  In coordination chemistry, the acylhydrazone ligands attracted the chemists due to their potential behaviour in magnetochemistry (Yu et al., 2010;Guo et al., 2010). The choice of N-acylhydrazonyl derivatives was suggested by publications indicating that compounds with such groups might have anti-tumoural activities (Rollas & Kucukguzel 2007). Against this background and to ascertain the molecular structure of title compound, the crystallographic study has been carried out.
The ORTEP plot of the molecule is shown in Fig. 1 (Allen et al., 1987).

Experimental
A mixture of salicylaldehyde and freshly distilled thioglycollic acid in 1:1.2 mole ratio was dissolved by heating on a water bath and let stand two days. The product was washed with water and recrystallized.

Refinement
H atoms bonded to O were isotropically refined and the other H atoms were positioned geometrically (C-H=0.93-0.98 Å) and allowed to ride on their parent atoms, with 1.2 U eq (C).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > σ(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.