Synthesis, crystal structure determination, Hirshfeld surface and crystal void analyses, inter­action energy calculations and energy frameworks of N-(2-chloro­phen­yl)-N′-propano­ylthio­urea

The title compound, C₁₀H₁₁ClN₂S, consists of a chloro­phenyl ring and a propanoyl moiety bridged over a thio­urea functional group. The dihedral angle between the planar propinoyl and thio­urea groups is 8.33 (14)°, and they are oriented at 48.50 (14) and 56.09 (6)° with respect to the phenyl ring. The intra­molecular N—H⋯O hydrogen bond forms an S(6) ring motif. In the crystal, N—H⋯S hydrogen bonds link two mol­ecules, enclosing R²₂(8) ring motifs, into centrosymmetric dimers. π–π stacking inter­actions help to consolidate the packing. Hirshfeld surface analysis revealed that the most important contributions for crystal packing are H⋯H (39.2%), H⋯Cl/Cl⋯H (15.8%), H⋯S/S⋯H (14.2%) and H⋯C/C⋯H (9.9%) inter­actions. The volume of the crystal voids and the percentage of free space were calculated to be 105.62 ų and 9.33%, showing that there is no large cavity in the crystal packing. Computational methods indicated an N—H⋯S hydrogen-bonding energy of −53.5 kJ mol⁻¹. Evaluations of the electrostatic, dispersion and total energy frameworks indicate that the crystal cohesion is dominated by electrostatic energy contributions.

1. Chemical context

Thio­urea is an important organic scaffold widely used in the development of therapeutic and industrially relevant mol­ecules. Several applications have been reported, and researchers continue to explore thio­urea derivatives in agriculture, gold recovery, analytical chemistry, and medicine (Rizki et al., 2019; Shakeel et al., 2016). Thio­urea derivatives exhibit diverse biological activities, including anti­cancer (Nammalwar et al., 2013), anti­thyroid, anti­malarial (Mishra & Batra, 2013), anti­fungal, anti­viral, anti­microbial, anti­oxidant, anti-allergic, anti-inflammatory, anti­septic, anti-leishmanial (Viana et al., 2017), and anti-hypertensive effects.

The thio­urea pharmacophore possesses unique chemical features, such as hydrogen-bonding groups (NH), a complementary sulfur site, and auxiliary binding positions at the 1,3-substituents, which enable strong and versatile inter­actions with biological targets (Mishra & Batra, 2013). Sulfur acts as a weak hydrogen-bond acceptor, while the bidentate nature of the thio­urea protons enhances hydrogen bonding, making thio­urea derivatives highly effective in medicinal chemistry (Nammalwar et al., 2013).

We became inter­ested in the properties and crystal structures of acyl­thio­ureas because of their notable biological activities, versatile metal-coordination behaviour, and ability to generate diverse supra­molecular hydrogen-bonding networks (Kumar et al., 2012; Gowda et al., 2012; Aly et al., 2007; Saeed et al., 2014, 2017). Numerous crystallographic investigations have demonstrated that acyl­thio­urea derivatives adopt diverse conformations consolidated through intra- and inter­molecular hydrogen bonding, particularly involving N—H⋯S and N—H⋯O inter­actions. These compounds also exhibit significant coordination versatility toward transition metals due to the presence of sulfur and carbonyl donor atoms. Detailed structural analyses of substituted acyl­thio­ureas have been reported in the literature (Arslan et al., 2003; Ghosh et al., 2010), highlighting the influence of the mol­ecular geometry and supra­molecular assembly on their physicochemical and biological properties.

Herein, we report the mol­ecular and crystal structures of N-(2-chloro­phen­yl)-N′-propano­ylthio­urea and Hirshfeld surface (HS) and crystal void analyses and inter­action energy calculations and energy frameworks.

2. Structural commentary

The title compound consists of a chloro­phenyl ring and propanoyl moiety bridged by a thio­urea functional group (Fig. 1). The planar propinoyl (O1/C8–C10) and thio­urea (S1/C7/N1/N2) groups (r.m.s. deviations of 0.039 and 0.013 Å, respectively) subtend a dihedral angle of 8.33 (14)°. The dihedral angles between the phenyl (C1–C6) ring and the propinoyl and thio­urea groups are 48.50 (14) and 56.09 (6)°, respectively. The Cl1 and N1 atoms are 0.0037 (8) and −0.0345 (23) Å away from the best plane of the phenyl ring, so they are coplanar. The bond lengths are in normal ranges (Allen et al., 1987) and comparable to those in the similar compounds N-(3-chloro­propion­yl)-N′-phenyl­thio­urea (Oth­man et al., 2010) and N-(2,6-di­methyl­phen­yl)-N′ propano­ylthio­urea (Yusof et al., 2012). The C1—N1—C7 [126.15 (19)°] and S1—C7—N1 [125.21 (18)°] bond angles are significantly wider, while the N1—C7—N2 [115.49 (19)°] and C2—C1—C6 [118.6 (2)°] are narrowed with respect to those found in these analogous structures. An intra­molecular N—H⋯O hydrogen bond (Table 1) forms an S(6) ring motif (Etter et al., 1990) (Fig. 2).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1N⋯O1	0.86 (2)	1.92 (2)	2.632 (3)	140 (3)
N2—H2N⋯S1^i	0.85 (2)	2.57 (2)	3.412 (2)	171 (3)
Symmetry code: (i) .

Figure 1 The asymmetric unit with atom-numbering scheme and 50% probability ellipsoids.

Figure 2 A partial packing diagram showing the intra­molecular N—H⋯O and inter­molecular N—H⋯S hydrogen bonds as dashed lines illustrating the intra­molecular S(6) and inter­molecular R2^2(8) ring motifs.

3. Supra­molecular features

In the crystal, N—H⋯S hydrogen bonds (Table 1) link the mol­ecules, enclosing R₂²(8) ring motifs (Etter et al., 1990), into centrosymmetric dimers (Fig. 2). Weak π–π stacking inter­actions between parallel phenyl rings, with a centroid-to-centroid distance of 4.1188 (17) Å, help to consolidate the packing.

The inter­molecular inter­actions in the crystal were visualized by carrying out the Hirshfeld surface (HS) analysis using CrystalExplorer 17.5 (Spackman et al., 2021). Fig. 3 shows the Hirshfeld surface with several neighboring mol­ecules in the crystal. The white surface indicates contacts with distances equal to the sum of van der Waals radii, and the red and blue colours indicate distances shorter (in close contact) or longer (distinct contacts) than the van der Waals radii, respectively. The red spots indicate their roles as the respective donors and/or acceptors atoms in hydrogen bonding, as discussed above. The π–π stacking inter­actions are shown in Fig. 4 by the presence of the adjacent red and blue triangles.

Figure 3 View of the three-dimensional Hirshfeld surface plotted over dnorm in the range −0.3374 to 1.1449 a.u.

Figure 4 Hirshfeld surface plotted over shape-index showing the π–π inter­actions.

The overall two-dimensional fingerprint plot is shown in Fig. 5a and those delineated into H⋯H, H⋯Cl/Cl⋯H, H⋯S/S⋯H, H⋯C/C⋯H, H⋯O/O⋯H, C⋯C, C⋯Cl/Cl⋯C, S⋯C/C⋯S, N⋯C/C⋯N, N⋯S/S⋯N, O⋯Cl/Cl⋯O, H⋯N/N⋯H, O⋯O and S⋯S inter­actions are illustrated in Fig. 5b–r, respectively. According to the two-dimensional fingerprint plots, the H⋯H, H⋯Cl/Cl⋯H, H⋯S/S⋯H and H⋯C/C⋯H contacts make the most significant contributions to the HS, at 39.2%, 15.8%, 14.2% and 9.9%, respectively (Fig. 5).

Figure 5 The full two-dimensional fingerprint plots for the title mol­ecule, showing (a) all inter­actions, and delineated into (b) H⋯H, (c) H⋯Cl/Cl⋯H, (d) H⋯S/S⋯H, (e) H⋯C/C⋯H, (f) H⋯O/O⋯H, (g) C⋯C, (h) C⋯Cl/Cl⋯C, (i) C⋯S/S⋯C, (j) C⋯N/N⋯C, (k) N⋯S/S⋯N, (l) O⋯Cl/Cl⋯O, (m) H⋯N/N⋯H, (n) C⋯O/O⋯C, (o) N⋯O/O⋯N, (p) O⋯O and (r) S⋯S inter­actions. The di and de values are the closest inter­nal and external distances (in Å) from given points on the Hirshfeld surface.

The strength of the crystal packing depends on the tight packing of the mol­ecules, which results insignificant voids. To check the strength of the crystal, a void analysis was performed. The volume of the crystal voids (Fig. 6a,b) and the percentage of free space in the unit cell were calculated as 105.62 ų and 9.33%, respectively. Thus, the crystal packing appears compact.

Figure 6 Crystal voids viewed down the (a) a-axis and (b) b-axis directions.

The inter­molecular inter­action energies are calculated using CE–B3LYP/6–31G(d,p) energy model available in CrystalExplorer17.5 (Spackman et al., 2021), where a cluster of mol­ecules is generated by applying crystallographic symmetry operations with respect to a selected central mol­ecule within the radius of 3.8 Å by default. The total inter­molecular energy (E_tot) is the sum of electrostatic (E_ele), polarization (E_pol), dispersion (E_dis) and exchange-repulsion (E_rep) energies (Turner et al., 2015) with scale factors of 1.057, 0.740, 0.871 and 0.618, respectively (Mackenzie et al., 2017). The hydrogen-bonding inter­action energies (in kJ mol⁻¹) for N2—H2N⋯S1 were calculated to be −70.5 (E_ele), −12.5 (E_pol), −19.9 (E_dis), 77.0 (E_rep) and −53.5 (E_tot).

Energy frameworks combine the calculation of inter­molecular inter­action energies with a graphical representation of their magnitudes. They were constructed for E_ele (red cylinders), E_dis (green cylinders) and E_tot (blue cylinders) (Fig. 7a,b,c). Evaluation of the electrostatic, dispersion and total energy frameworks indicates that the stabilization of the crystal structure is dominated by the electrostatic energy contributions.

Figure 7 The energy frameworks for a cluster of mol­ecules viewed down the b-axis showing the (a) electrostatic energy, (b) dispersion energy and (c) total energy diagrams. The cylindrical radius is proportional to the relative strength of the corresponding energies and they were adjusted to the same scale factor of 80 with cut-off value of 5 kJ mol^−1 within 2 × 2 × 2 unit cells.

4. Synthesis and crystallization

N-(2-Chloro­phen­yl)-N′-propano­ylthio­urea was synthesized by adding dropwise a solution of propinoyl chloride (0.10 mol) in acetone (30 ml) to a suspension of ammonium thio­cyanate (0.10 mol) in acetone (30 ml), and then stirred for 2 h. The reaction mixture was then refluxed for 30 min. After cooling to room temperature, a solution of 2-chloro­aniline (0.10 mol) in acetone (10 ml) was added and the solution refluxed for 3 h. After completion of the reaction (monitored by TLC), the reaction mixture was poured into acidified cold water. The precipitate was filtered under suction, washed with water and dried under vacuum. Colourless crystals suitable for X-ray analysis were obtained by slow evaporation of aceto­nitrile solution. White solid, yield 84%, m.p. 393–394 K. ¹H NMR (400 MHz, CDCl₃): δ (ppm) 12.30 (s, 1H), 9.77 (s, 1H), 7.23–7.61 (m, 4H, Ar-H), 1.45 (t, 3H, CH₃), 2.10 (q, 2H, CH₂). ¹³C NMR (100 MHz, CDCl₃): δ (ppm) 24.4, 31.3, 124.0, 127.0, 128.0, 132.9, 137.4, 141.2, 171.0, 178.7.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The NH hydrogen atoms were located from difference-Fourier maps and refined isotropically. The C-bound H-atom positions were calculated geometrically at distances of 0.93 Å (for aromatic CH), 0.97 Å (for methyl­ene CH) and 0.96 Å (for methyl CH) and refined using a riding model applying the constraint U_iso(H) = k × U_eq(C), where k = 1.5 for methyl hydrogens and 1.2 for the other H atoms.

Table 2
Experimental details

Crystal data
Chemical formula	C10H11ClN2OS
Mr	242.72
Crystal system, space group	Monoclinic, P21/c
Temperature (K)	293
a, b, c (Å)	11.971 (1), 4.1187 (6), 23.100 (2)
β (°)	96.44 (1)
V (Å^3)	1131.8 (2)
Z	4
Radiation type	Mo Kα
μ (mm^−1)	0.50
Crystal size (mm)	0.50 × 0.48 × 0.36
Data collection
Diffractometer	Oxford Diffraction Xcalibur with Sapphire CCD detector
Absorption correction	Multi-scan (CrysAlis RED; Oxford Diffraction, 2006)
Tmin, Tmax	0.790, 0.842
No. of measured, independent and observed [I > 2σ(I)] reflections	3971, 2291, 1809
Rint	0.012
(sin θ/λ)max (Å^−1)	0.625
Refinement
R[F^2 > 2σ(F^2)], wR(F^2), S	0.043, 0.113, 1.10
No. of reflections	2291
No. of parameters	143
No. of restraints	2
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å^−3)	0.31, −0.25
Computer programs: CrysAlis CCD and CrysAlis RED (Oxford Diffraction, 2006), SHELXT2014/5 (Sheldrick, 2015a), SHELXL2018/3 (Sheldrick, 2015b), ORTEP-3 for Windows and WinGX publication routines (Farrugia, 2012) and PLATON (Spek, 2020).

Supporting information

Computing details

N-(2-Chlorophenyl)-N'-propanoylthiourea

Crystal data

C10H11ClN2OS	F(000) = 504
Mr = 242.72	Dx = 1.424 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 11.971 (1) Å	Cell parameters from 2737 reflections
b = 4.1187 (6) Å	θ = 2.6–27.6°
c = 23.100 (2) Å	µ = 0.50 mm^−1
β = 96.44 (1)°	T = 293 K
V = 1131.8 (2) Å^3	Prism, colorless
Z = 4	0.50 × 0.48 × 0.36 mm

Data collection

Oxford Diffraction Xcalibur with Sapphire CCD detector diffractometer	1809 reflections with I > 2σ(I)
Rotation method data acquisition using ω scans.	Rint = 0.012
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)	θmax = 26.4°, θmin = 2.6°
Tmin = 0.790, Tmax = 0.842	h = −14→11
3971 measured reflections	k = −3→5
2291 independent reflections	l = −21→28

Refinement

Refinement on F^2	2 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.043	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.113	w = 1/[σ^2(Fo^2) + (0.0471P)^2 + 0.6068P] where P = (Fo^2 + 2Fc^2)/3
S = 1.10	(Δ/σ)max < 0.001
2291 reflections	Δρmax = 0.31 e Å^−3
143 parameters	Δρmin = −0.25 e Å^−3

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cl1	0.35101 (6)	1.1838 (2)	0.21334 (3)	0.0615 (2)
S1	0.18007 (5)	1.06937 (19)	0.00913 (3)	0.0500 (2)
O1	0.09369 (15)	0.5612 (6)	0.17325 (7)	0.0683 (6)
N1	0.24754 (16)	0.8040 (6)	0.11267 (8)	0.0434 (5)
N2	0.05779 (16)	0.7857 (6)	0.08305 (8)	0.0414 (5)
C1	0.36338 (18)	0.8729 (6)	0.11114 (9)	0.0381 (5)
C2	0.4218 (2)	1.0438 (6)	0.15665 (9)	0.0402 (6)
C3	0.5355 (2)	1.1061 (7)	0.15738 (11)	0.0516 (7)
H3	0.573956	1.219918	0.188205	0.062*
C4	0.5911 (2)	0.9986 (7)	0.11229 (11)	0.0548 (7)
H4	0.667268	1.042699	0.112239	0.066*
C5	0.5347 (2)	0.8257 (7)	0.06703 (11)	0.0540 (7)
H5	0.572970	0.751932	0.036720	0.065*
C6	0.4216 (2)	0.7618 (7)	0.06657 (10)	0.0466 (6)
H6	0.384135	0.643217	0.036089	0.056*
C7	0.16460 (19)	0.8754 (6)	0.07130 (9)	0.0375 (5)
C8	0.02653 (19)	0.6352 (7)	0.13210 (10)	0.0435 (6)
C9	−0.0974 (2)	0.5694 (7)	0.13048 (10)	0.0487 (6)
H9A	−0.118402	0.402049	0.101768	0.058*
H9B	−0.138509	0.764965	0.118118	0.058*
C10	−0.1317 (2)	0.4623 (9)	0.18860 (12)	0.0687 (9)
H10A	−0.111548	0.627255	0.217244	0.103*
H10B	−0.093709	0.263737	0.200384	0.103*
H10C	−0.211450	0.427960	0.185048	0.103*
H1N	0.227 (3)	0.712 (7)	0.1431 (10)	0.082*
H2N	0.004 (2)	0.821 (8)	0.0569 (11)	0.082*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0633 (5)	0.0837 (6)	0.0373 (3)	0.0074 (4)	0.0045 (3)	−0.0067 (3)
S1	0.0348 (3)	0.0719 (5)	0.0415 (3)	−0.0044 (3)	−0.0031 (2)	0.0171 (3)
O1	0.0401 (10)	0.1185 (19)	0.0455 (10)	0.0024 (11)	0.0009 (8)	0.0306 (11)
N1	0.0303 (10)	0.0661 (15)	0.0327 (10)	−0.0021 (10)	−0.0020 (8)	0.0078 (10)
N2	0.0293 (10)	0.0591 (13)	0.0348 (10)	0.0000 (10)	−0.0015 (7)	0.0061 (9)
C1	0.0301 (11)	0.0487 (15)	0.0343 (11)	0.0039 (10)	−0.0015 (9)	0.0078 (10)
C2	0.0384 (13)	0.0499 (15)	0.0312 (11)	0.0041 (11)	−0.0015 (9)	0.0059 (10)
C3	0.0421 (14)	0.0605 (18)	0.0487 (14)	−0.0061 (13)	−0.0105 (11)	0.0023 (13)
C4	0.0298 (13)	0.070 (2)	0.0634 (17)	−0.0012 (13)	0.0018 (11)	0.0100 (15)
C5	0.0426 (14)	0.0710 (19)	0.0498 (14)	0.0126 (14)	0.0112 (11)	0.0060 (14)
C6	0.0400 (13)	0.0608 (17)	0.0382 (12)	0.0042 (12)	0.0004 (10)	−0.0028 (12)
C7	0.0340 (12)	0.0453 (14)	0.0322 (11)	0.0009 (10)	−0.0013 (9)	−0.0009 (10)
C8	0.0382 (13)	0.0564 (17)	0.0356 (12)	0.0023 (12)	0.0032 (10)	0.0035 (11)
C9	0.0368 (13)	0.0617 (17)	0.0474 (13)	−0.0064 (13)	0.0039 (10)	0.0025 (13)
C10	0.0550 (17)	0.099 (3)	0.0533 (16)	−0.0196 (18)	0.0133 (13)	0.0054 (17)

Geometric parameters (Å, º)

Cl1—C2	1.736 (2)	C3—H3	0.9300
S1—C7	1.672 (2)	C4—C5	1.378 (4)
O1—C8	1.213 (3)	C4—H4	0.9300
N1—C7	1.331 (3)	C5—C6	1.377 (3)
N1—C1	1.420 (3)	C5—H5	0.9300
N1—H1N	0.858 (17)	C6—H6	0.9300
N2—C8	1.380 (3)	C8—C9	1.504 (3)
N2—C7	1.387 (3)	C9—C10	1.513 (3)
N2—H2N	0.847 (17)	C9—H9A	0.9700
C1—C6	1.384 (3)	C9—H9B	0.9700
C1—C2	1.387 (3)	C10—H10A	0.9600
C2—C3	1.384 (3)	C10—H10B	0.9600
C3—C4	1.371 (4)	C10—H10C	0.9600
C7—N1—C1	126.15 (19)	C5—C6—C1	120.5 (2)
C7—N1—H1N	115 (2)	C5—C6—H6	119.8
C1—N1—H1N	118 (2)	C1—C6—H6	119.8
C8—N2—C7	128.42 (19)	N1—C7—N2	115.49 (19)
C8—N2—H2N	114 (2)	N1—C7—S1	125.21 (18)
C7—N2—H2N	118 (2)	N2—C7—S1	119.27 (16)
C6—C1—C2	118.6 (2)	O1—C8—N2	122.6 (2)
C6—C1—N1	121.8 (2)	O1—C8—C9	122.6 (2)
C2—C1—N1	119.6 (2)	N2—C8—C9	114.7 (2)
C3—C2—C1	121.0 (2)	C8—C9—C10	113.3 (2)
C3—C2—Cl1	119.47 (19)	C8—C9—H9A	108.9
C1—C2—Cl1	119.52 (18)	C10—C9—H9A	108.9
C4—C3—C2	119.4 (2)	C8—C9—H9B	108.9
C4—C3—H3	120.3	C10—C9—H9B	108.9
C2—C3—H3	120.3	H9A—C9—H9B	107.7
C3—C4—C5	120.3 (2)	C9—C10—H10A	109.5
C3—C4—H4	119.8	C9—C10—H10B	109.5
C5—C4—H4	119.8	H10A—C10—H10B	109.5
C6—C5—C4	120.1 (2)	C9—C10—H10C	109.5
C6—C5—H5	119.9	H10A—C10—H10C	109.5
C4—C5—H5	119.9	H10B—C10—H10C	109.5
C7—N1—C1—C6	−56.9 (4)	C2—C1—C6—C5	−1.2 (4)
C7—N1—C1—C2	126.0 (3)	N1—C1—C6—C5	−178.4 (2)
C6—C1—C2—C3	0.8 (4)	C1—N1—C7—N2	−179.4 (2)
N1—C1—C2—C3	178.0 (2)	C1—N1—C7—S1	−1.3 (4)
C6—C1—C2—Cl1	−179.63 (19)	C8—N2—C7—N1	0.6 (4)
N1—C1—C2—Cl1	−2.4 (3)	C8—N2—C7—S1	−177.7 (2)
C1—C2—C3—C4	0.3 (4)	C7—N2—C8—O1	0.4 (5)
Cl1—C2—C3—C4	−179.3 (2)	C7—N2—C8—C9	−179.5 (2)
C2—C3—C4—C5	−1.0 (4)	O1—C8—C9—C10	10.7 (4)
C3—C4—C5—C6	0.5 (4)	N2—C8—C9—C10	−169.4 (3)
C4—C5—C6—C1	0.6 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···O1	0.86 (2)	1.92 (2)	2.632 (3)	140 (3)
N2—H2N···S1^i	0.85 (2)	2.57 (2)	3.412 (2)	171 (3)

Symmetry code: (i) −x, −y+2, −z.