Crystal structure of (2E)-N-methyl-2-(2-oxo-1,2-dihydroacenaphthylen-1-ylidene)hydrazinecarbothioamide

In the title compound, the acenapthylene ring system and the hydrazinecarbothioamide unit (=N—NH—C=S—NH–) are essentially coplanar, making a dihedral angle of 1.59 (9)°. The molecular conformation is stabilized by two weak intramolecular hydrogen bonds (N—H⋯O and N—H⋯N), which generate S(6) and S(5) ring motifs.

In the title compound, C 14 H 11 N 3 OS, the acenaphthylene ring system and hydrazinecarbothioamide unit (=N-NH-C=S-NH-) are essentially coplanar [with maximum deviations from their mean planes of À0.009 (2) and 0.033 (2) Å , respectively], and make a dihedral angle of 1.59 (9) . The molecular conformation is stabilized by two weak intramolecular hydrogen bonds (N-HÁ Á ÁO and N-HÁ Á ÁN), which generate S(6) and S(5) ring motifs. In the crystal, molecules are linked by N-HÁ Á ÁS hydrogen bonds, forming chains along [010]. The chains are linked via pairs of C-HÁ Á ÁO hydrogen bonds, enclosing R 2 2 (10) ring motifs, and C-HÁ Á Á interactions, forming a three-dimensional framework. The absolute structure of the title compound was determined by resonant scattering.

Chemical context
The design and synthesis of thiosemicarbazones are of considerable interest because of their versatile chemistry and various biological activities, such as antitumor, antibacterial, antiviral, antiamoebic and antimalarial (Kelly et al., 1996). They comprise an intriguing class of chelating molecules, which possess a wide range of beneficial medicinal properties (Prabhakaran et al. 2008). Thiosemicarbazones are a versatile class of ligands that have been studied for their biological activity , their interesting binding motifs (Lobana et al., 2009) and their use as ligands in catalysis (Xie et al., 2010). In view of their biological importance, the crystal structure of the title compound has been determined and the results are presented herein.

Structural commentary
The molecular structure of the title compound is illustrated in Fig. 1. The atoms of both the acenaphthylene ring system and the =N-NH-C=S-NH-segment are essentially coplanar, the maximum deviations from their mean planes being À0.009 (2) and 0.033 (2) Å for atoms C12 and C14, respec-tively. The dihedral angle between the benzene and cyclopentane rings of the acenapthalene unit is 1.59 (9) . The molecular structure is stabilized by N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds, forming S(6) and S(5) ring motifs, respectively (Table 1 and Fig. 1).

Synthesis and crystallization
An ethanolic solution of N-methylhydrazinecarbothioamide (0.01 mol) was added to an ethanolic solution (50 ml) containing acenaphthylene-1,2-dione (0.01 mol). The mixture was refluxed for 2 h during which time a yellow precipitate separated out. The reaction mixture was then cooled to room temperature and the precipitate was filtered off. It was then washed with ethanol and dried under vacuum. The yield of the isolated product was 89%. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the title compound in ethanol at room temperature.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were fixed geom- The molecular structure of the title compound, with the atom labelling. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen bonds are shown as dashed lines (see Table 1 for details). Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
The crystal packing of the title compound viewed along the a axis. Hydrogen bonds are shown as dashed lines (see Table 1 for details; H atoms not involved in hydrogen bonding have been omitted for clarity).

sup-1
Acta Cryst. Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); 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) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009). 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.