Crystal structure and Hirshfeld surface analysis of a new dithioglycoluril: 1,4-bis(4-methoxyphenyl)-3a-methyltetrahydroimidazo[4,5-d]imidazole-2,5(1H,3H)-dithione

In the title dithioglycoluril derivative, there is a difference in the torsion angles between the thioimidazole moiety and the methoxyphenyl groups on either side of the molecule [C—N—Car—Car = 116.9 (2) and −86.1 (3)°]. The N—C—N bond angle on one side of the dithioglycoluril moiety is slightly smaller than the one on the opposite side [110.9 (2)° cf. 112.0 (2)°], probably as a result of the steric effect of the methyl group.


Supramolecular features
In the crystal, N-HÁ Á ÁS hydrogen bonds link neighbouring molecules to form chains propagating along the c-axis direction (Table 1 and Fig. 2). The chains are linked by C-HÁ Á ÁS hydrogen bonds, forming layers parallel to the bc plane ( Fig. 3 and Table 1). In turn, the layers are linked by C-HÁ Á Á interactions involving a methoxy methyl H atom (H12B) and a 4-methoxyphenyl ring (C13-C18); see Table 1. These interactions result in the formation of a supramolecular threedimensional architecture (Fig. 3).

Figure 2
A view along the b axis of the N-HÁ Á ÁS hydrogen-bonded chain in the crystal of the title compound.

Figure 1
A view of the molecular structure of the title compound, with the atom labelling. Displacement ellipsoids are drawn at the 30% probability level. mapped over d norm (Fig. 4), the red spots indicate contacts shorter than the sum of the van der Waals radii with negative d norm , blue regions represent contacts longer than the sum of van der Waals radii with negative d norm , while white regions correspond to intermolecular distances close to the sum of the van der Waals radii with d norm equal to zero. The most intense red spots on the surface of the title compound are found around the thione S and N-H groups of the compound, which play a role in the hydrogen bonding interactions in the crystal (Table 1 and Fig. 2). The less intense red spots (Fig. 4), are observed around the ring carbon atoms resulting from C-HÁ Á ÁS and C-HÁ Á Á short contacts. The two-dimensional fingerprint plots (Fig. 5) show the overall contribution of the various interactions and those delineated into HÁ Á ÁH, SÁ Á ÁH/ HÁ Á ÁS, CÁ Á ÁH/HÁ Á ÁC, OÁ Á ÁH/HÁ Á ÁO and NÁ Á ÁH/HÁ Á ÁN contacts. Apart from the non-directional HÁ Á ÁH contacts (41.3%), the highest contribution to the Hirshfeld surface is from SÁ Á ÁH/HÁ Á ÁS contacts (26.1%).

Database survey
A search of the Cambridge Structural Database (CSD, Version 5.39, February 2019) for thioglycoluril found two molecules similar to the title compound: 1,6-dipivaloyl-3,3a,4,6a-tetramethyltetrahydroimidazo[4,5-d]imidazole-2,5-(1H,3H)-dithione (refcode ADEMOL; Duspara et al., 2001) and 1,6-diacetyl-3,4,7,8-tetramethyl-2,5-dithiogylcoluril (SOLQIT; Cow, 1998). In both compounds, large polar groups are substituted on adjacent sides of the imidazole ring, resulting in steric hindrance and distortion of the C-N-C angles. The C-N-C bond angles between the thione carbon and the N-substituted groups are ca 119.8 and 125.4 in ADEMOL and 122.6 and 125.4 in SOLQIT. In the title compound, the C5-N3-C6 and C1-N1-C13 bond angles are 124.8 (2) and 126.1 (2) , respectively, showing only little distortion. The thione bond lengths [C5 S2 and C1 S1 are both 1.674 (2) Å ] in the title compound are longer than in the reference compounds (1.650-1.664 Å ). This is probably due to the fact that all of the imidazole nitrogen atoms in the reference compounds are substituted. The presence of unsubstituted imidazole nitrogens in the title compound promotes conjugation between the lone pairs of electrons on the nitrogen atom and the C S -electrons and hence stretches the C S bond. The C-N bond lengths around the thione group of the title compound The Hirshfeld surface of the title compound mapped over d norm , with an arbitrary colour scale of À0.3207 to 1.4281.    Table 1 for details). For clarity, H atoms not involved in these interactions have been omitted.

Synthesis and crystallization
The title compound was synthesized according to the reported method Douglass & Dains, 1934;Oyeka et al., 2018). A solution of cinnamoyl chloride (0.02 mol) dissolved in 40 ml acetone was mixed with a 30 ml acetone solution of potassium thiocyanate (0.02 mol). The reaction mixture was refluxed for 30 min to give a suspension of cinnamoyl isothiocyanate, which was then left to cool to room temperature. 4-Methoxyaniline (0.02 mol) was dissolved in 40 ml of acetone and the resulting solution was mixed with the suspension of cinnamoyl isothiocyanate, and the mixture was stirred for 2 h. The resultant lemon-green solution was filtered and left at room temperature for 96 h to obtain colourless plate-like crystals of the title compound.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Hydrogen atoms were placed at idealized positions (N-H = 0.86 Å , C-H = 0.93-0.98 Å ) and refined using a riding model with U iso (H) = 1.5U eq (C-methyl) and 1.2U eq (C,N) for other H atoms.