Crystal Structure, Hirshfeld Surface Analysis and Computational Studies of Thiazolidin-4-one derivative: (Z)-5-(4-Chlorobenzylidene)-3-(2-ethoxyphenyl) -2-thioxothiazolidin-4-one

The title compound (Z)-5-(4-chlorobenzylidene)-3-(2-ethoxyphenyl)-2-thioxothiazolidin-4-one (CBBTZ) was characterized by X-ray single crystal diffraction, H NMR and C NMR spectra. Theoretical investigations were carried out using HF and DFT levels of theory at 6-31G(d,p) basis set. The X-ray structure is compared with that computed. The calculated geometrical parameters are in good agreement with those determined by X-ray diffraction. The dihedral angle between the two benzene rings is 16.89(5)° indicating that the structure is non planar. The molecule exhibits intraand intermolecular contacts of type C–H···O, C–H···S and C–H···Cl. The intercontacts in the crystal structure are explored using Hirshfeld surfaces analysis method.


Introduction
Heterocyclic compounds containing five membered rings with nitrogen, sulfur, and oxygen atoms have been investigated since a long time for their important properties.2][3] Among these types of compounds, 4-thiazolidinones have been shown to have various significant activities.2][13] Consequently, (Z)-5-(4-chlorobenzylidene) -3-(2-ethoxyp-henyl) -2-thioxothiazolidin-4-one (CBBTZ) is a interesting member of the above-mentioned molecules containing delocalized π electrons with donor and acceptor groups.Appropriate electron donor and acceptor groups and π-conjugated system allow the CBBTZ to exhibit the asymmetric electronic distribution which leads to an increased charge transfer.
Recently, some studies have been carried out on CBBTZ.The optical, electrochemical and X-ray photoelectron spectroscopy (XPS) characterization of CBBTZ has been explored and CBBTZ thin films with electronic properties were also studied as an exciton blocking layer in CuPc/C60 heterojunction solar cells. 14,15n this context, and in continuation of our works on thiazolidinones molecules, this study was aimed to report the structural properties and intermolecular interactions of CBBTZ. 1,16. Experiment and Computational Methods
set. 26,27 The spatial coordinate positions of the title compound, as obtained from X-ray structural investigation, were used as initial coordinates for the theoretical calculations.

1. Description of the Crystal Structure
Selected experimental geometrical parameters are summarized in Tables 2, 3 and 4. The molecular structure with atomic labelling (thermal ellipsoids are drawn at 50% probability) is depicted in Fig. 1.The thioxothiazol ring is essentially planar.The full molecule has a Z configuration about the C7=C8 double bond (Figure 1).This Z configuration of CBBTZ crystal is stabilized by intramolecular hydrogen bonds C-H•••O and C-H•••S.The CC bond lengths in the phenyl rings have average value of 1.38 Å obtained by X-ray diffraction and calculated mean values of 1.40 Å and 1.39 Å obtained with B3LYP and HF, respectively.The double bond of C7=C8 is characterized by the experimental distance of 1.332(8) Å.The thiazole ring contains two C-S bonds, namely S1-C8 [1.729( 7) Å] and S1-C10 [1.717 (7) Å].C9-O2 distance shows a typical double bond character with bond length of 1.198(7) Å.The bond lengths are consistent with previous phenyl ring-containing studies. 1 In the thiazole moiety formed by C8, C9, C10, N1 and S1

X-Ray Structure Determination
X-Ray diffraction study was done on single crystal diffractometer Kappa CCD Nonius.X-Ray data have been measured using graphite monochromated MoKα radiation (λ = 0.71073 Å) at ambient temperature.The program SHELXS-97 was used to solve the structure by direct methods. 17Then, full-matrix least-squares refinement using SHELXL-97 revealed the final structure. 18ydrogen atoms were located in their calculated positions.Figure 1 shows the structure of CBBTZ along with the atomic labeling using ORTEP visualization program. 19For highlighting intra-and intermolecular interactions, Hirshfeld Surface analyses were performed and fingerprint plots were drawn using Crystal Explorer. 20rystallographic details and refinement data are summarized in Table 1.

3. Theoretical Approach
Throughout this study, Gaussian 03 software 21 and Gauss-View program 22 have been used to perform molecular modelling.B3LYP 23,24 and HF 25 methods were used to optimize the molecular structure of the title compound in the ground state using the 6-31G(d,p) basis atoms, the average value of bond angles is 108(5)°.In addition, delocalization of the π electrons in CBBTZ is confirmed by C-C-C, C-N-C and C-C-N bond angles which are around 120°.The torsion angle between the two benzene (C1-C6) and (C11-C16) rings is 16.89(5)°.The ethoxyphenyl group is twisted slightly, with a C9-N1-C11-C12 torsion angle of 82.9(12)°.The two moieties chlorobenzene and thioxothiazolidinone are nearly planar according to the dihedral angle C5-C6-C7-C8 of 16.4( 18)° (X-ray diffraction) and from 172.5° to 179.5° (theoretical calculation).As mentioned in our previous work, 16 the chirality of this kind of compounds is highlighted by the value of the dihedral angle formed by the heterocyclic ring and the aryl bound at the nitrogen atom.In the present study, this angle is 95.8°.As we can easily see from the above results, there is a good correlation between the experimental and theoretical structural results.The observed differences are due to the fact that experimental results belong to the solid phase, while theoretical calculations belong to the gas phase of isolated molecules.The molecular packing in the crystal structure of CBBTZ is stabilized by intermolecular interactions forming a three-dimensional network (Figure 2).and theoretical geometries.This can be explained by considering that the theoretical calculations were carried out in a gaseous phase, whereas the X-ray diffraction study was performed on the compound in the solid form.Figure 4 compares the calculated structure to that obtained by X-ray diffraction.

4. Hirshfeld Surface Analysis
Hirshfeld surface (HS) analysis represents a unique approach towards an understanding of different interactions in the crystal structure and is a necessary tool in crystal engineering.In addition to the HS analysis, the fingerprint plots also provide some useful quantitative information about the individual contribution of each intermolecular interaction in the crystal packing.The intra-and intermolecular interactions of CBBTZ crystal are quantified using HS analysis.The three-dimensional HS generated for structure of CBBTZ crystal is presented in Fig. 6.The red contacts highlight the intermolecular interactions with distances closer than the sum of the van der Waals radii, while white indicates contacts near the van der Waals separation, and blue depicts longer contacts. 28Figure 7 shows Hirshfeld surfaces mapped for CBBTZ compound with the shape index property (a) and with d norm selected intermolecular contacts (b).The full fingerprint plot for the CBBTZ crystal and the contribution of each type of interaction to the total HS are presented in Figure 8 displaying surfaces that were mapped over d norm (0.242 to 1.414).
As seen in Figure 7      The quantitative results of the HS analysis for the CBBTZ crystal are presented in Fig. 9 which gives a de-tailed quantitative analysis of all intra-and intermolecular contacts contributing to the HS.In general, a good agreement was observed between the calculated geometrical parameters (with B3LYP) and that of reported similar derivatives.All the calculated data and experimental results of the studied molecule are useful in the application in fundamental research in chemistry and photovoltaic cells in the future.Finally, HS analysis and fingerprint plots are a unique way for understanding the contribution of individual types of interactions within the crystal structure.More theoretical calculations can be performed on this compound to assess other properties especially in the photovoltaic field.

Supplementary Material
Crystallographic data for the structure reported in this article have been deposited with Cambridge Crystallographic Data Center, CCDC 1044524.Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge, CBZ IEZ, UK.Facsimile (44) 01223 336 033, E-mail: deposit@ccdc.cam.ac.uk or http//www.ccdc.com.ac.uk/deposit.

Figure 3
Figure 3 depicts the calculated molecular structure of CBBTZ using the B3LYP/6-31G(d,p) level of theory.Theoretical geometric parameters by HF and DFT levels of theory using 6-31G(d,p) basis set are given in Tables 2, 3 and 4 together with the experimental ones.The theoretical structural results of CBBTZ have a little different values compared with corresponding experimental results.Thus, bond length values of the thiazole ring N1-C9 and N1-C10 are 1.411 and 1.377 Å computed with B3LYP, with respect to the X-ray results 1.379(8) and 1.330(7) Å, respectively.In the same context, calculated distances S1-C8 (1.765 Å) and S1-C10 (1.763 Å) are comparable to the experimental values (1.729(7) and 1.716(7) Å).The C-C distances in the two aromatic cycles vary from 1.380(8) to 1.401(8) Å compared to the theoretical values which vary from 1.389 to 1.415 Å.According to the above results, deviations of 0.01 Å for bond lengths and 3° for bond and torsion angles are found between experimental

Figure 1 .
Figure 1.Structure of CBBTZ with atomic labeling scheme (ellipsoids are drawn at 50% probability).For clarity, the hydrogen atoms are omitted.

Figure 2 .
Figure 2. A perspective view of the crystal packing in the unit cell.View along the c axis.

Figure 4 .
Figure 4. Atom-by-atom superimposition of the structures calculated (solid line) over the X-ray structure (dashed line) for CBBTZ.

Figure 6 .
Figure 6.View of the HS for CBBTZ molecule.

Figure 7 .
Figure 7. HS mapped for CBBTZ compound with (a) the shape index property (b) d norm selected intermolecular contacts.

Figure 8 .
Figure 8.The 2D fingerprint plots showing the percentage contribution of the individual types of interaction to the total HS area.

Figure 9 .
Figure 9. Quantitative results of different intra-and intermolecular interactions contributing to the HS.

Table 2 .
Experimental and calculated bond lengths

Table 3 .
Experimental and calculated bond angles

Table 4 .
Experimental and calculated dihedral angles