Crystal structure, Hirshfeld surface and computational study of 1-(9,10-dioxo-9,10-dihydroanthracen-1-yl)-3-propanoylthiourea

In the title compound, the thiourea chromophore is planar to an r.m.s deviation of 0.032 Å with the thiolate sulfur atom being the most deviated. Bifurcated N—H⋯O intramolecular hydrogen bonds result in an S(6) supramolecular synthon. In the crystal, molecules are linked by N—H⋯O intermolecular hydrogen-bonding interactions and stabilized by C—H⋯π and π–π interactions.


Structural commentary
The title compound crystallizes in the orthorhombic crystal system and Pbca space group. The molecular structure (Fig. 1) shows a central thiourea chromophore flanked on either side by methylene and anthraquinone units. The central thiourea moiety is essentially planar with an r.m.s deviation of 0.032 Å with the thiolate S atom being the most deviated out of the plane with a deviation of 0.044 (3) Å . The torsion angles between the thiourea and the adjourning methylene and anthraquinone moieties are À177.5 (2) and À140.8 (2) , respectively, indicating that the anthraquinone moiety is slightly deviated from the thiourea plane, compared to the methylene moiety. The C1-N1-C5 bond angle of 126.09 (19) subtended at the N1 atom is smaller than the less encumbered C2-N2-C1 angle [129.79 (19) ] subtended at N2 and larger than the central N1-C1-N2 [114.5 (2) ] bond angle subtended at the thiolate C1 carbon atom. The C1-N2 bond [1.395 (3) Å ] is slightly longer than C1-N1 [1.364 (3) Å ]. The thiourea carbonyl oxygen and imine groups are involved in a strong intramolecular N1-H1Á Á ÁO1 hydrogen bond (Table 1). The second amine nitrogen N2 is also involved in a hydrogen-bonding S(6) graph-set (Kansiz et al., 2022) interaction.
Explorer 17.5 software (Turner et al., 2017). The Hirshfeld surfaces mapped over d norm and shape-index were generated according to a procedure described by Tan et al. (2019) and used for further analysis of the intermolecular interactions. The HS mapped over d norm shows the most intense red regions around the thiourea N-H groups resulting from the amine-N-HÁ Á ÁO (anthraquinone) hydrogen-bonding interactions (Fig. 3a). Other intense red spots can be identified around the thiourea carbonyl oxygen and resulting from carbonyl C17-H17Á Á ÁO12 intermolecular interaction. Apart from the intense red spots, there are a number of other less intense red spots found around the alkyl C3 atom resulting from C3-H3BÁ Á ÁO2 intermolecular interaction. Other intermolecular interactions in the Hirshfeld surface are the anthraquinone C-HÁ Á ÁS(thiourea) and anthraquinone-C-HÁ Á ÁH(alkyl) interactions shown respectively as pink and green dotted lines in Fig. 3b. The anthraquinoneinteractions can be seen in Fig. 3c. The CÁ Á ÁH/HÁ Á ÁC contacts in the molecule are responsible for the molecular packing in the supramolecular structure and are the result of the C-HÁ Á Áp andinteractions (Tan & Tiekink, 2020) and are depicted by mapping the structure over the shape-index isosurface as shown in Fig. 3d. The C-HÁ Á Á interactions appear as hollow orange areas (Á Á ÁH-C) and bulging blue areas (C-HÁ Á Á) in the compound. The small blue regions surrounding a bright orange spot within the anthroquinone rings of the molecule indicatestacking interactions. The overall two-dimensional fingerprint plot (Spackman & McKinnon, 2002;Tan & Tiekink, 2020) and those delineated into HÁ Á ÁH, HÁ Á ÁO/OÁ Á ÁH, HÁ Á ÁC/CÁ Á ÁH, CÁ Á ÁC, SÁ Á ÁH/HÁ Á ÁS and CÁ Á ÁO/OÁ Á ÁC interactions are illustrated in Fig. 4, and their percentage contributions are presented in Table 2. The overall fingerprint plot comprises all intermolecular contacts in the molecule and exhibits a shield-like profile with two symmetric spikes on each side of a triangular protrusion. These spikes are also observed in the fingerprint plots for the OÁ Á ÁH/HÁ Á ÁO contacts, which make a 19.5% contribution to the overall surface contact, but not in the other surface contacts. These spikes are due to the C-HÁ Á ÁO and N2-H2Á Á ÁO3 hydrogen-bonding interactions in the crystal structure of the title compound. HÁ Á ÁH contacts are the single highest contributor to the overall surface with a 38.0% contribution and and result from C-HÁ Á ÁH and HÁ Á ÁH dispersion interactions. The other major surface contacts are CÁ Á ÁH/HÁ Á ÁC (13.0%) SÁ Á ÁH/HÁ Á ÁS (10.8%), and CÁ Á ÁC (11.2%), showing that CÁ Á ÁH and intermolecular contacts contribute significantly to the overall stability of the supramolecular architecture in the crystal structure (Ekowo et al., 2020;Izuogu et al., 2020). The overall and individual two-dimensional fingerprint plots for intermolecular contacts in the crystal structure.

Figure 3
Hirshfeld surfaces mapped over (a), (b) and (c) d norm and (d) shape-index showing intermolecular atom-to-atom andinteractions in the crystal structure.

Interaction energy calculations
The interaction energies between pairs of molecules within the crystal of the title compound were calculated by adding up the four energy components, viz. electrostatic (E ele ), polarization (E pol ), dispersion (E dis ), and exchange repulsion (E rep ) (Tan et al., 2019;Ayiya & Okpareke, 2021). The energies were obtained by calculating the wave function of each pair of molecules or atoms at the B3LYP/6-31G(d,p) level of theory (Ayiya & Okpareke, 2021;Izuogu et al., 2020). Quantitative estimations of the strength and nature of the intermolecular interactions in title compound crystal with individual energy components (E ele , E pol , E dis , and E rep ) as well as the sum of the energy components E tot are presented in Table 3. This shows that the dispersive component of the energy makes the most significant contribution to the total interaction energy profile in the crystal structure, probably due to the intermolecular dispersive interactions resulting from thestacking of adjacent anthraquinone ring systems in the crystal. The electrostatic component is the second highest contributor to the total interaction energy and probably results from the CÁ Á ÁH, HÁ Á ÁH and van der Waals interactions. A graphical representation of the magnitude of the interaction energies is presented in Fig, 5a-d in the form of energy frameworks to show the supramolecular architecture using cylindrical poles joining the centroids of molecular pairs. The red, green, and blue color-coded frameworks in Fig. 5a, 5b, and 5c, respectively, represent the E ele , E dis , and E tot , energy components for intermolecular interactions in crystal of the title compound, while Fig. 5d shows the annotated E tot energy. The magnitude of the cylindrical pipes indicates the significance of the E ele energy component to the total interaction energy and the molecular packing in the crystal.

Synthesis and crystallization
A solution of propionyl chloride (1.85 g, 0.02 mol) dissolved in 40 mL acetone was mixed with 30 mL of an acetone solution of potassium thiocyanate (1.94 g, 0.02 mol). The reaction mixture was refluxed for 30 min to give a suspension of propionylisothiocyanate, which was left to cool to room temperature. 1-Aminoanthraquinone (4.47 g, 0.02 mol) was dissolved in 40 mL of acetone and the resulting solution was mixed with the suspension of propionylisothiocyanate, and the mixture was stirred for 2 h. The resultant reddish suspension was filtered, and left at room temperature for 96 h to obtain a reddish crystalline solid of the title compound.

Refinement
Crystal data, collection and structure refinement details are summarized in Perspective views of the energy frameworks of the title compound showing (a) electrostatic, (b) dispersion, (c) total energy and (d) annotated total energy. The cylindrical radius is proportional to the relative strength of the corresponding energies and they were adjusted to the same scale factor of 100 with a cut-off value of 5 kJmol À1 within 2 x 2 x 2 unit cells. placed in calculated positions and were included in the refinement using the riding-model approximation with U iso (H) set to 1.2U eq (C). The nitrogen-bound H atoms were located in the difference-Fourier maps and refined freely with appropriate RIGU restraints placed on the bonds.  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.