Benzyl 2-(benzylsulfanyl)benzoate

In the title compound, C21H18O2S, the central aromatic ring makes dihedral angles of 5.86 (12) and 72.02 (6)° with the rings of the terminal O-benzyl and S-benzyl groups, respectively. The dihedral angle between the peripheral phenyl rings is 66.16 (6)°. In the crystal, molecules are linked by pairs of C—H⋯O hydrogen bonds, forming inversion dimers. These dimers are linked via C—H⋯π interactions, forming a three-dimensional network.

In the title compound, C 21 H 18 O 2 S, the central aromatic ring makes dihedral angles of 5.86 (12) and 72.02 (6) with the rings of the terminal O-benzyl and S-benzyl groups, respectively. The dihedral angle between the peripheral phenyl rings is 66.16 (6) . In the crystal, molecules are linked by pairs of C-HÁ Á ÁO hydrogen bonds, forming inversion dimers. These dimers are linked via C-HÁ Á Á interactions, forming a threedimensional network.

Ratković Comment
Thiosalicylic acid and its derivatives find potential application in numerous disease treatments, in particular inflammatory, allergic and respiratory diseases (Bernardelli et al., 2005) as well as Ras tumor growth inhibitors (Halaschek-Wiener et al., 2003). Ketones derived from thiosalicylic acids have application as bile acid transport inhibitors (Sadao et al., 2000). In continuation of our work on structural and biological properties of thiosalicylic derivatives and their metal complexes (Radić et al., 2012) here we present the crystal structure of the novel ligand benzyl 2-(benzylsulfanyl)benzoate.
The bond lengths and angles in the title compound are within the expected ranges. The dihedral angle between aromatic rings of the central thiosalicylic and terminal O-benzyl group is 5.86 (12)° indicating a nearly co-planar orientation of these two fragments. On the other hand, the ring of the S-benzyl group is significantly twisted with respect to the central ring forming a dihedral angle of 72.02 (6)°. In the previously reported crystal structures with S-benzyl derivatives of thiosalicylic acid the analogue dihedral angle varies from 13.4 to 88.9°, suggesting the free rotation of the S-benzyl ring around the single bonds of the C3-S1-C15-C16 fragment. The specific property of the present compound is that the atoms S1, C15 are C16 all lie in the plane of the central ring within 0.03 Å. In the cases of similar uncoordinated (Sillanpää et al., 1994;Alhadi et al., 2010] as well as coordinated ligands (Radić et al., 2012;Lucena et al., 1996) the corresponding atom C16 is significantly out of the central ring plane (1.57 Å in average).
The pair of C14-H14···O2 interactions connects inversion related molecules into dimers (Table 1, Fig. 2). This connection is reinforced by means of C-H···π interactions involving the O-benzyl C13-H13 donor and the S-benzyl ring from an inversion-related molecule as acceptor (Table 1; Cg3 is the centroid of the S-benzyl ring). The S-benzyl ring also serves as a π-acceptor for C-H donors of a neighboring molecular pair; in that way the pairs of molecules further arrange into chain by C4-H4···Cg3 interactions (Table 1, Fig. 2). The molecules are further associated into a threedimensional structure by C-H···π interactions which engage two remaining phenyl rings as π-acceptors (Table 1, Cg1 and Cg2 are centroids of central thiosalicylic and terminal O-benzyl rings, respectively).

Experimental
The thioacid ligand was prepared by alkylation of thiosalicylic acid by means of the corresponding alkyl halogenides in alkaline water-ethanol solution. Thiosalicylic acid (1 mmol) was added to a 100 cm 3 round bottom flask containing 50 cm 3 of a 30% solution of ethanol in water and stirred. A solution of NaOH (2 mmol in 5 cm 3 of water) was added to the acid suspension, whereupon the solution became clear. The corresponding benzyl halogenide (2 mmol) was dissolved in 5 cm 3 of ethanol and transferred to the stirred solution. The resulting mixture was kept overnight at 60°C. The reaction mixture was transffered into a beaker and ethanol was evaporated off on a water bath. Diluted hydrochloric acid (2 mol/dm 3 ) was added to the resulting water solution and S-benzyl thiosalicylic acid was precipitated as a white powder. The obtained acid was filtered off and washed with plenty of distilled water. The product was dried under vacuum overnight. Crystals of the title compound suitable for X-ray determination were obtained by slow evaporation of a benzyl alcohol solution, which unexpectedly resulted in the esterification of the carboxylic group of thiosalicylic acid.

Refinement
H atoms bonded to C atoms were placed at geometrically calculated positions and refined using a riding model. C-H distances were fixed to 0.93 and 0.97 Å from aromatic and methylene C atoms, respectively. The U iso (H) values were equal to 1.2 times U eq of the corresponding aromatic C(sp 2 ) and methylene C(sp 3 ) atoms.