Mukesh M Jotani1, Chien Ing Yeo2, Edward R T Tiekink3. 1. Department of Physics, Bhavan's Sheth R. A. College of Science, Ahmedabad, Gujarat 380001, India. 2. Department of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia. 3. Department of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia ; Centre for Chemical Crystallography, Faculty of Science and Technology, Sunway University, 47500 Bandar Sunway, Selangor Darul Ehsan, Malaysia.
Abstract
In the title thio-semicarbazone, C11H15N3S, the p-tolyl-N-H and imino-N-H groups are anti and syn, respectively, to the central thione-S atom. This allows for the formation of an intra-molecular p-tolyl-N-H⋯N(imino) hydrogen bond. The mol-ecule is twisted with the dihedral angle between the p-tolyl ring and the non-hydrogen atoms of the N=CMe2 residue being 29.27 (8)°. The crystal packing features supra-molecular layers lying in the bc plane whereby centrosymmetric aggregates sustained by eight-membered thio-amide {⋯HNCS}2 synthons are linked by further N-H⋯S hydrogen bonds. Layers are connected via methyl-C-H⋯π inter-actions. The supra-molecular aggregation was further investigated by an analysis of the Hirshfeld surface and comparison made to related structures.
In the title n class="Chemical">thio-semicarbazone, n class="Gene">C11H15N3S, the p-tolyl-N-H and imino-N-H groups are anti and syn, respectively, to the central thione-S atom. This allows for the formation of an intra-molecular p-tolyl-N-H⋯N(imino) hydrogen bond. The mol-ecule is twisted with the dihedral angle between the p-tolyl ring and the non-hydrogen atoms of the N=CMe2 residue being 29.27 (8)°. The crystal packing features supra-molecular layers lying in the bc plane whereby centrosymmetric aggregates sustained by eight-membered thio-amide {⋯HNCS}2 synthons are linked by further N-H⋯S hydrogen bonds. Layers are connected via methyl-C-H⋯π inter-actions. The supra-molecular aggregation was further investigated by an analysis of the Hirshfeld surface and comparison made to related structures.
The reaction between ann class="Chemical">alcohol or pan> class="Chemical">amine (primary or secondary) with N-alkyl- or N-aryl-isothiocyanides usually results in the formation of thiocarbamides. For example, in the case of reactions involving a monofunctional alcohol, the reaction proceeds in the following manner: R—OH + R′N=C=S → ROC(=S)N(H)R′ (Ho et al., 2005 ▸). Often, reactions are facilitated by initially employing an alkali metal hydroxide as the base and later adding an acid, e.g. HCl (Ho et al., 2005 ▸). Such molecules are of interest as when deprotonated, they can function as effective thiolate ligands for phosphanegold(I) derivatives, which display biological activity. For example, Ph3PAu[SC(O–alkyl)=N(aryl)] compounds exhibit significant cytotoxicity against a variety of cancer cell lines and mechanistic studies show that they can kill cancer cells by initiating a variety of apoptotic pathways, both extrinsic and intrinsic (Yeo, Ooi et al., 2013 ▸; Ooi, Yeo et al., 2015 ▸). Related species, i.e. Ph3PAu[SC(O–alkyl)=N(p-tolyl)], exhibit potency against Gram-positive bacteria (Yeo, Sim et al., 2013 ▸). Over and above these considerations, systematic studies into the structural chemistry of these molecules, which have proven relatively easy to crystallize, have been of some interest in crystal engineering endeavours (Ho et al., 2006 ▸; Kuan et al., 2008 ▸). In the course of studies to increase the functionality of the thiocarbamide molecules, bipodal {1,4-[MeOC(=S)N(H)]2C6H4} was successfully synthesized along with binuclear phosphanegold(I) complexes (Yeo, Khoo et al., 2015 ▸). Recent attempts at expanding this chemistry by using thiourea as an aminedonor have been undertaken. As reported very recently, 1:2 reactions between thiourea and R′N=C=S resulted in the isolation of salts containing 1,2,3-thiazole-based cations resulting from 1:1 cyclizations (Yeo, Tan et al., 2015 ▸). Herein, the product of an analogous reaction involving a bifunctional amine, i.e. H2NNH2 (hydrazine) with (p-tolyl)N=C=S, conducted in acetone solution, is described, namely the thiosemicarbazone, (I). Molecules related to (I) and especially their metal complexes continue to attract attention owing to potential biological activity (Dilworth & Hueting, 2012 ▸; Lukmantara et al., 2013 ▸; Su et al., 2013 ▸).
Structural commentary
The molecular structure of (I), Fig. 1 ▸, comprises three planar regions. The central NC(=S)N chromophore (the r.m.s. deviation of the fitted atoms is 0.0020 Å) has anti- and n class="Gene">syn-dispositionpan>s of the N1- anpan>d N2-bound pan> class="Disease">H atoms, respectively, with respect to the central thione-S1 atom. The N1-bound H atom is syn to the imino-N3 atom allowing for the formation of a five-membered loop via an N1—H⋯N3 hydrogen bond, Table 1 ▸. The central plane forms dihedral angles of 23.49 (4)° with the propan-2-ylideneamino residue (N=CMe2; r.m.s. deviation for the C3N atoms = 0.0002 Å) and 43.30 (5)° with the p-tolyl ring. Overall, the molecule is twisted as quantified by the dihedral angle between the outer planes of 29.27 (8)°.
Figure 1
The molecular structure of (I) showing displacement ellipsoids at the 70% probability level.
Table 1
Hydrogen-bond geometry (, )
Cg1 is the centroid of the C2C7 ring.
DHA
DH
HA
DA
DHA
N1H1NN3
0.88(1)
2.09(2)
2.572(2)
114(1)
N1H1NS1i
0.88(1)
2.87(2)
3.5618(17)
137(2)
N2H2NS1ii
0.88(2)
2.57(2)
3.4373(16)
169(2)
C8H8CCg1iii
0.98
2.81
3.716(2)
154
Symmetry codes: (i) ; (ii) ; (iii) .
Two n class="Gene">P21/c polymorphs have beenpan> reported for the parenpan>t compound, i.e. having a phenpan>yl rather thanpan> a p-pan> class="Chemical">tolyl substituent (Jian et al., 2005 ▸; Venkatraman et al., 2005 ▸); the structure of (I) also crystallizes in the P21/c space group. As revealed from the data collated in Table 2 ▸, there is a high degree of concordance in the key bond lengths and angles for the three molecules, as might be expected. However, there are some notable differences in the torsion-angle data as well as in the dihedral angles between the three least-squares planes discussed above, Table 2 ▸. From these and the overlay diagram shown in Fig. 2 ▸, it is apparent that the molecular structure of (I) more closely matches that observed in the polymorph reported by Venkatraman et al. (2005 ▸) rather than that described by Jian et al. (2005 ▸). This conclusion is also vindicated in the unit cell data, i.e. a = 12.225 (3), b = 7.618 (2), c = 11.639 (3) Å, β = 102.660 (4)° reported for the former (Venkatraman et al., 2005 ▸).
Table 2
Geometric data (, ) for (I) and two polymorphs of (II)
Parameter
(I)
Form a of (II)a
Form b of (II)b
N2N3
1.397(2)
1.386(2)
1.392(2)
C1S1
1.6873(18)
1.6816(17)
1.6826(17)
C1N1
1.350(2)
1.337(2)
1.343(2)
C1N2
1.350(2)
1.359(2)
1.348(2)
C2N1
1.422(2)
1.420(2)
1.425(2)
C9N3
1.280(2)
1.279(2)
1.276(2)
C1N1C2
127.79(16)
129.98(14)
127.97(14)
C1N2N3
117.72(15)
118.17(14)
118.33(14)
N2N3C9
117.91(15)
118.85(15)
117.73(14)
S1C1N1
125.45(14)
126.00(13)
125.75(13)
S1C1N2
120.00(14)
119.37(13)
119.50(12)
N1C1N2
114.54(16)
114.63(15)
114.74(15)
S1C1N2N3
169.57(12)
177.46(12)
170.56(12)
C1N1C2C3
132.2(2)
153.87(18)
131.10(19)
C1N2N3C9
165.78(16)
168.43(16)
165.85(15)
CN2S / C3N
23.49(4)
13.19(8)
22.42(9)
CN2S / aryl
43.30(5)
39.26(6)
43.90(6)
C3N / aryl
29.27(8)
40.15(8)
30.18(8)
Notes: (a) Jian et al. (2005 ▸); (b) Venkatraman et al. (2005 ▸).
Figure 2
Overlay diagram of the molecules in (I), red image, and (II), forms a (green) and b (blue). The molecules have been overlapped so that the central NC(=S)N chromophores are coincident.
NMR invesitgations
The conformation of (I) was also investigated inn class="Chemical">CDCl3 solutionpan> by NMR methods. Assignpan>menpan>ts were made with the aid of the inclass="Chemical">pan>terpretative program, Chemdraw Ultra (CambridgeSoft Corporationpan>, 2002 ▸). Onpan> the basis of multiple pan> class="Chemical">1H and 13C{1H} resonances for the methyl groups of the propan-2-ylideneamino residue, it appears that the (propan-2-ylideneamino)thiourea residue has a locked configuration, consistent with the persistence of the intramolecular N1—H⋯N3 hydrogen bond in CDCl3 solution.
Supramolecular features
In the crystal, N—H⋯S and C—H⋯π interactions provide identifiable points of contact between molecules; these interactions are quantified in Table 1 ▸. Centrosymmetrically related molecules are connected by pairs of n class="Chemical">amide-N2—H⋯S1 pan> class="Chemical">hydrogen bonds, forming eight-membered thioamide {⋯HNCS}2 synthons. These are connected into supramolecular layers in the bc plane by amide-N1—H⋯S1 hydrogen bonds so that the S1 atom accepts two hydrogen bonds, Fig. 3 ▸. The p-tolyl groups protrude to either side of each layer and inter-digitate along the a axis with adjacent layers allowing for the formation of methyl-C8—H⋯π(C2–C7) interactions, thereby consolidating the three-dimensional architecture, Fig. 4 ▸.
Figure 3
Supramolecular layer in the bc plane in the crystal packing of (I). Centrosymmetric aggregates mediated by eight-membered thioamide {⋯HNCS}2 synthons (shown as orange dashed lines) are linked by additional amide-N—H⋯S hydrogen bonds, shown as blue dashed lines.
Figure 4
A view of the unit cell contents of (I) shown in projection down the b axis. Supramolecular layers, illustrated in Fig. 3 ▸, are linked via C—H⋯π interactions, shown as purple dashed lines, leading to a three-dimensional architecture.
Analysis of the Hirshfeld surfaces
The crystal packing was further investigated by an analysis of the Hirshfeld surface (Spackman & Jayatilaka, 2009 ▸) employing CrystalExplorer (Wolff et al., 2012 ▸). Fingerprint plots (Rohl et al., 2008 ▸) were calculated, as were the electrostatic potentials un class="Gene">sing TONTO (Spackmanpan> et al., 2008 ▸; Jayatilaka et al., 2005 ▸) integrated into CrystalExplorer; the electrostatic potenpan>tials were mapped onpan> the Hirshfeld surfaces upan> class="Gene">sing the STO–3G basis set at the level of Hartree–Fock theory over a range of ±0.075 au.
Two views of the Hirshfeld surface mapped over d
norm are shown in Fig. 5 ▸
a and b. The deep-red n class="Disease">depressions at the S1 anpan>d N2 atoms (Fig. 5 ▸
a) conpan>firm their role as anpan> acceptor anpan>d pan> class="Species">donor in the hydrogen-bonding scheme, respectively. This is also evident from the dark-red and blue regions, respectively, on the Hirshfeld surface mapped over the calculated electrostatic potential (Fig. 5 ▸
c). The diminutive red spots near S1 and N1 (Fig. 5 ▸
b) indicate their involvement in the intermolecular N—H⋯S hydrogen bond.
Figure 5
Views of the Hirshfeld surface for (I): (a) and (b) mapped over d
norm, and (c) mapped over the calculated electrostatic potential.
The overall two-dimensional fingerprint plot (Fig. 6 ▸
a) and those delineated into H⋯H, S⋯H/H⋯S, N⋯H/H⋯N and C⋯H/H⋯C H⋯H (Fig. 6 ▸
b–d, respectively) interactions operating in the crystal structure of (I) are illustrated in Fig. 6 ▸; the relative contributions are summarized in Table 3 ▸. The prominent pair of sharp spikes of equal length (d
e + d
i = 2.45 Å; Fig. 6 ▸
b) with a 15.2% contribution due to S⋯H/H⋯S contacts to the Hirshfeld surfaces also suggest the presence of these interactions in the crystal packing. The light-red regionnear N3 (Fig. 5 ▸
a) and diminutive red spot near N1—H (Fig. 5 ▸
b) are consistent with relatively smaller contributions from N⋯H/H⋯N contacts, i.e. 2.5 and 3.0%, respectively, and are indicative of the weak intramolecular n class="Chemical">hydrogen bonpan>d. The strenpan>gth of such anpan> interactionpan> canpan> be visualized from the 2D fingerprint plot corresponpan>ding to N⋯H/ H⋯N conpan>tacts (Fig. 6 ▸
c). The bright-orpan> class="Gene">ange spot in the surface mapped with d
e (within a red circle in Fig. 7 ▸) about the aryl ring and a light-blue region around the tolyl-hydrogen atom, H8C (Fig. 7 ▸), suggest a contribution from the C—H⋯π interaction (Table 1 ▸). This is also evident through distinct pair of ‘wings’ in the fingerprint plot corresponding to C⋯H/H⋯C contacts (Fig. 6 ▸
d). The wing at the top, left belongs to C—H donors, while that at the bottom, right corresponds to the surface around π-acceptors with 11.3 and 7.8% contribution from C⋯H and H⋯C contacts, respectively. The H⋯H contacts reflected in the middle of scattered points in Fig. 6 ▸
e provide the most significant contribution, i.e. 57.0%, to the Hirshfeld surface arising from a side-ways approach. The small, flat segments delineated by the blue outline in the surface mapped with curvedness (Fig. 8 ▸) and the small (i.e. 0.7%) contribution from C⋯C contacts to the surface indicates the absence of π–π stacking interactions in the structure.
Figure 6
2D Fingerprint plots for (I): (a) full, (b) delineated to show S⋯H/H⋯S, (c) N⋯H/H⋯N, (d) C⋯H/H⋯C, and (e) H⋯H interactions.
Table 3
Relative contribution (%) to intermolecular interactions calculated from the Hirshfeld surface
Contact
Contribution
HH
57.0
SH/HS
15.2
NH/HN
5.5
CH/HC
19.1
CC
0.7
NN
1.4
CN
0.8
CS
0.2
others
0.1
Figure 7
View of the Hirshfeld surface for (I) mapped over d
e.
Figure 8
Hirshfeld surfaces for (I) mapped over curvedness.
Database survey
According to a search of the Cambridge Structural Database (Groom & Allen, 2014 ▸), there are no direct analogues of (I), either in the coordinated or uncoordinated form. As mentioned in the Structural commentary, the parent compound has been characterized in two polymorphic forms (Jian et al., 2005 ▸; Venkatraman et al., 2005 ▸). The parent compound, n class="Chemical">LH, has also beenpan> observed to coordinate pan> class="Chemical">metal centres. Thus, monodentate coordination via the thione-S atom was observed in a neutral complex [ZnCl2(LH)2] (Bel’skii et al., 1987 ▸). By contrast, a chelating mode via thione-S and imino-N atoms was observed in each of the charged complexes [CoBr(LH)2]Br (Dessy et al., 1978 ▸) and [(η6-p-cymene)RuCl(LH)]Cl (Su et al., 2013 ▸). The most closely related structure having the p-tolyl substituent but variations at the imino-N atom is one where one methyl group has been substituted by a phenyl (Zhang et al., 2011 ▸). This is also a twisted molecule with the dihedral angle between the p-tolyl and NC3 residues being 65.44 (7)°.
Synthesis and crystallization
To p-n class="Chemical">tolyl isothiocyanpan>ate (Sigma–Aldrich; 10 mmol, 1.49 g) inpan> class="Chemical">acetone (20 ml) was added hydrazine monohydrate (Sigma–Aldrich; 10 mmol, 0.76 ml). The resulting mixture was stirred for 4 h at room temperature. Both chloroform (20 ml) and acetonitrile (20 ml) were then added, and the resulting mixture left for slow evaporation. Light-brown crystals were obtained after 2 weeks. Yield: 2.012 g (91%). M.p. 412–413 K. 1H NMR (400 MHz, CDCl3, 298 K): 9.19 (s, br, 1H, NH—N), 8.56 (s, br, 1H, NH), 7.49 (d, 2H, m-aryl, J = 8.28 Hz), 7.17 (d, 2H, o-aryl, J = 8.24 Hz), 2.34 (s, 3H, aryl-CH3), 2.05 (s, 3H, CH3), 1.94 (s, 3H, CH3). 13C NMR (400 MHz, CDCl3, 298 K): 176.4 [CS], 149.6 [C(CH3)2], 135.8 [C], 135.4 [C], 129.3 [C], 124.5 [C], 25.3 [CH3], 21.0 [aryl-CH3], 16.9 [CH3, syn to N—H]. IR (cm−1): ν(N—H) 3240, 3168 (m), ν(C=N) 1514 (vs), ν(C—N) 1267 (s), ν(C=S) 1188 (vs).
Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4 ▸. n class="Chemical">Carbon-bound pan> class="Disease">H-atoms were placed in calculated positions (C—H = 0.95–0.98 Å) and were included in the refinement in the riding model approximation, with U
iso(H) set to 1.2–1.5U
eq(C). The N-bound H atoms were located in a difference Fourier map but were refined with a distance restraint of N—H = 0.88±0.01 Å, and with U
iso(H) set to 1.2U
eq(N).
Table 4
Experimental details
Crystal data
Chemical formula
C11H15N3S
Mr
221.32
Crystal system, space group
Monoclinic, P21/c
Temperature (K)
100
a, b, c ()
13.7289(13), 7.4341(7), 11.5757(11)
()
102.690(1)
V (3)
1152.58(19)
Z
4
Radiation type
Mo K
(mm1)
0.25
Crystal size (mm)
0.12 0.05 0.03
Data collection
Diffractometer
Bruker SMART APEX CCD
Absorption correction
Multi-scan (SADABS; Sheldrick, 1996 ▸)
Tmin, Tmax
0.970, 0.993
No. of measured, independent and observed [I > 2(I)] reflections
10739, 2646, 2052
Rint
0.050
(sin /)max (1)
0.650
Refinement
R[F2 > 2(F2)], wR(F2), S
0.041, 0.098, 1.02
No. of reflections
2646
No. of parameters
147
No. of restraints
2
H-atom treatment
H atoms treated by a mixture of independent and constrained refinement
max, min (e 3)
0.27, 0.27
Computer programs: APEX2 and SAINT (Bruker, 2008 ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2014/7 (Sheldrick, 2015 ▸), ORTEP-3 for Windows (Farrugia, 2012 ▸), QMol (Gans Shalloway, 2001 ▸), DIAMOND (Brandenburg, 2006 ▸) and publCIF (Westrip, 2010 ▸).
Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S2056989015017624/hb7507sup1.cifStructure factors: contains datablock(s) I. DOI: 10.1107/S2056989015017624/hb7507Isup2.hklClick here for additional data file.Supporting information file. DOI: 10.1107/S2056989015017624/hb7507Isup3.cmlCCDC reference: 1425975Additional supporting information: crystallographic information; 3D view; checkCIF report
H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.098
w = 1/[σ2(Fo2) + (0.0332P)2 + 0.7356P] where P = (Fo2 + 2Fc2)/3
S = 1.02
(Δ/σ)max < 0.001
2646 reflections
Δρmax = 0.27 e Å−3
147 parameters
Δρmin = −0.27 e Å−3
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.