Crystal structure of a new monoclinic polymorph of 2,4-di­hydroxy­benzaldehyde 4-methyl­thio­semi­carbazone

A new monoclinic (P2₁/c) polymorph of the title compound has the same overall conformation as a previously reported (Cc) form with the exception of the conformation of the outer hy­droxy H atom. This difference results in very different crystal packing based on hydrogen bonding, i.e. supra­molecular tubes in the new form as opposed to a three-dimensional architecture in the Cc form.

Abstract

The title compound, C₉H₁₁N₃O₂S, is a second monoclinic (P2₁/c) polymorph of the previously reported Cc form [Tan et al. (2008b ▸). Acta Cryst. E64, o2224]. The mol­ecule is non-planar, with the dihedral angle between the N₃CS residue (r.m.s. deviation = 0.0816 Å) and the benzene ring being 21.36 (4)°. The conformation about the C=N bond [1.292 (2) Å] is E, the two N-bound H atoms are anti, and the inner hy­droxy O-bound and outer amide N-bound H atoms form intra­molecular hydrogen bonds to the imine N atom. Crucially, the H atom of the outer hy­droxy group is approximately syn to the H atom of the benzene C atom connecting the two C atoms bearing the hy­droxy substituents. This arrangement enables the formation of supra­molecular tubes aligned along [010] and sustained by N—H⋯O, O—H⋯S and N—H⋯S hydrogen bonds; the tubes pack with no specific inter­actions between them. While the mol­ecular structure in the Cc form is comparable, the H atom of the outer hy­droxy group is approximately anti, rather than syn. This different orientation leads to the formation a three-dimensional architecture based on N—H⋯O and O—H⋯S hydrogen bonds.

Chemical context  

In a review of the biological applications of metal complexes of thio­semicarbazone derivatives, Dilworth & Hueting (2012 ▸) highlighted the various biological roles exhibited by this class of compound. Thus, these may have therapeutic potential, for example being cytotoxic and capable of inhibiting both ribonuclease reductase and topoisomerase II. Metal complexes of thio­semicarbazones can also function as diagnostic agents in imaging/diagnostic applications. In the context of this bio­logical relevance, the specific title compound of the present report has been coordinated as an N,O,S-tridentate dianion to zinc(II) and the resultant complex explored for activity against prostate cancer (Tan et al., 2012 ▸).

The crystal structure of the title mol­ecule has been reported previously as a Cc polymorph (Tan et al., 2008b ▸). Following on from previous structural work on related compounds (Affan et al., 2013 ▸), the title compound was prepared and routine screening of the crystals indicated that this crystallizes as a second monoclinic (P2₁/c) polymorph. The crystal and mol­ecular structure of the second form of the title compound is reported herein and compared with the original Cc polymorph.

Structural commentary  

The mol­ecular structure found in the new monoclinic (P2₁/c) polymorph is shown in Fig. 1 ▸. The mol­ecule is non-planar with a twist about the C1—N2 bond being evident as seen in (i) the N3—N2—C1—S1 torsion angle of 164.83 (11)° and (ii) the dihedral angle between the N₃CS residue (r.m.s. deviation = 0.0816 Å) and benzene ring of 21.36 (4)°. The conformation about the C3=N3 bond [1.292 (2) Å] is E, the two N-bound H atoms are anti, and within the mol­ecule, both the O1- and N1-bound H atoms form intra­molecular hydrogen bonds to the imine-N3 atom, Table 1 ▸. The O2—H2o H atom is approximately syn to the C6—H6 H atom.

Figure 1.

The mol­ecular structure of the title compound in the P2₁/c polymorph, showing the atom labelling and displacement ellipsoids at the 70% probability level.

Table 1. Hydrogen-bond geometry (, ).

DHA	DH	HA	D A	DHA
O1H1oN3	0.83(2)	1.97(2)	2.6992(17)	147(2)
N1H1nN3	0.815(19)	2.35(2)	2.7080(19)	107.1(16)
O2H2oS1i	0.90(2)	2.37(2)	3.1918(12)	152(2)
N1H1nS1ii	0.815(19)	2.763(18)	3.3883(13)	134.9(17)
N2H2nO1iii	0.90(2)	2.08(2)	2.9527(17)	162(2)

Symmetry codes: (i) ; (ii) ; (iii) .

To a first approximation, the mol­ecular structure found in the Cc polymorph (Tan et al., 2008b ▸), reported to be isolated also from an ethanol solution, is similar, but two significant differences are noted. These are highlighted in the overlay diagram shown in Fig. 2 ▸. With the N3—N2—C1—S1 torsion angle being −172.5 (2)°, the twist about the C1—N2 bond deviates by about 8°, toward planarity, from that in the P2₁/c form. However, the dihedral angle between the N₃CS residue and benzene ring of 23.1 (9)° is a little wider in the Cc form as the terminal methyl group is slightly twisted out of the CN₃S plane: the C2—N1—C1—S1 torsion angle is −3.1 (5)° cf. to 1.2 (2)° in the P2₁/c form. The major and most significant difference arises in the relative orientation of the outer hy­droxy group where the H2o atom is anti to the C6—H6 H atom cf. approximately syn in the P2₁/c form. This has a major consequence upon the crystal packing in the two forms as discussed in §3.

Figure 2.

Overlay diagram of the mol­ecules in the P2₁/n polymorph (red image) and in the Cc form (blue). The mol­ecules have been overlapped so the benzene rings are coincident.

The calculated density for the P2₁/c form is 1.496 g cm⁻³ and the packing efficiency (KPI), calculated by PLATON (Spek, 2009 ▸), is 73.1%. These values are lower than the comparable values in the Cc form, i.e. 1.521 g cm⁻³ and 74.4%, respectively, suggesting that the Cc form is the more stable.

Supra­molecular features  

In the crystal packing of the P2₁/c polymorph, conventional hydrogen bonding inter­actions lead to the formation of a supra­molecular tube, Fig. 3 ▸ and Table 1 ▸. Here, the inner N2—H2n atom forms a hydrogen bond to a translationally related inner O1 atom, and the bifurcated S1 atom accepts hydrogen bonds from the outer, centrosymmetically related, O2—H2o and a translationally related, outer N1—H1n atom. The tubes are aligned along the b axis and pack with no specific inter­molecular inter­actions between them, Fig. 4 ▸. A distinctive crystal packing pattern is noted in the Cc polymorph (Tan et al., 2008b ▸). Here, the inner N2—H2n atom forms a hydrogen bond to a glide-related inner O1 atom, leading to a supra­molecular layer that stacks along the a axis. The S1 atoms project to one side of the layer and the outer O2—H2o atoms, with the anti disposition (see above), lie to the other. These form hydrogen bonds so that a three-dimensional architecture ensues, Fig. 5 ▸. In this scenario, the outer N1—H1n atom only participates in an intra­molecular hydrogen bond to the N3 atom, as does in the inner O1—H1o atom.

Figure 3.

Supra­molecular tube along the b axis in the structure of the P2₁/c polymorph sustained by N—H⋯O, O—H⋯S and N—H⋯S hydrogen bonds, shown as blue, orange and brown dashed lines, respectively (see Table 1 ▸ for details).

Figure 4.

View in projection down the b axis of the unit-cell contents of the P2₁/c polymorph, highlighting the packing of the supra­molecular tubes.

Figure 5.

View in projection down the b axis of the unit-cell contents of the Cc polymorph, highlighting the the stacking of the layers along the a axis, sustained by N—H⋯O hydrogen bonds (blue dashed lines), and their connection by O—H⋯S hydrogen bonds (orange dashed lines).

Database survey  

Given the inter­est in semi­thio­carbazones owing to their biological potential, it is not surprising that a search of Version 5.35 (plus May updates) of the Cambridge Crystallographic Database (Groom & Allen, 2014 ▸) revealed almost 100 hits for the CC(H)=NN(H)C(=S)N(H)C fragment. The only restriction in the search was that the heaviest atom be S. In the absence of this restriction there were nearly 400 hits. Of the smaller set of structures, there was only one pair of polymorphs, namely two triclinic (P ) forms for salicyl­aldehyde 4-phenyl­thio­semicarbazone, one with Z′ = 3 (Seena et al., 2008 ▸) and the other with Z′ = 2 (Rubčić et al., 2008 ▸). The most closely related structure in the literature is the N-Et derivative, reported twice (Tan et al., 2008a ▸; Hussein et al., 2014 ▸). This structure exhibits the same mol­ecular attributes as described above for the N-Me polymorphs, i.e. conformation, relative disposition of key atoms and intra­molecular hydrogen bonding.

Synthesis and crystallization  

A solution of 2,4-di­hydroxy­benzaldehyde (0.65 g, 4.75 mmol) in ethanol (20 ml) was added to a solution of 4-methyl-3-thio­semicarbazide (0.5 g, 4.75 mmol) in ethanol (20 ml). The resulting brown solution was refluxed with stirring for 2 h, and then filtered, washed with ethanol and dried in vacuo over silica gel. The filtrate was left to stand at room temperature for two days after which colourless block-like crystals were obtained (yield 0.79 g, 74%). M.p: 471–473 K. FT–IR (KBr, cm⁻¹) ν_max: 3377 (s, OH), 3190 (s, NH), 1615 (m, C=N), 1558 (s, C—O), 1012 (m, N—N), 1360, 845 (w, C=S). Analysis calculated for C₉H₁₁N₃O₂S: C, 47.94; H, 4.88; N, 18.64%. Found: C, 48.0; H, 4.68; N, 18.52%.

Refinement  

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. Carbon-bound H-atoms were placed in calculated positions (C—H = 0.95–0.98 Å) and included in the refinement in the riding-model approximation, with U _iso(H) =1.5U _eq(C) for methyl H atoms and = 1.2U _eq(C) for other H atoms. The O- and N-bound H-atoms were located in a difference Fourier map and freely refined.

Table 2. Experimental details.

Crystal data
Chemical formula	C9H11N3O2S
M r	225.27
Crystal system, space group	Monoclinic, P21/c
Temperature (K)	100
a, b, c ()	7.3058(2), 6.0582(1), 22.6041(6)
()	91.100(2)
V (3)	1000.27(4)
Z	4
Radiation type	Mo K
(mm1)	0.31
Crystal size (mm)	0.48 0.19 0.14
Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996 ▸)
T min, T max	0.866, 0.957
No. of measured, independent and observed [I > 2(I)] reflections	9696, 2302, 1950
R int	0.027
(sin /)max (1)	0.650
Refinement
R[F 2 > 2(F 2)], wR(F 2), S	0.035, 0.086, 1.06
No. of reflections	2302
No. of parameters	153
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
max, min (e 3)	0.30, 0.31

Computer programs: APEX2 and SAINT (Bruker, 2009 ▸), SHELXS2014 and SHELXL2014 (Sheldrick, 2008 ▸), ORTEP-3 for Windows (Farrugia, 2012 ▸), QMol (Gans Shalloway, 2001 ▸), DIAMOND (Brandenburg, 2006 ▸), PLATON (Spek, 2009 ▸ and publCIF (Westrip, 2010 ▸).

Supplementary Material

CCDC reference: 960620

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Crystal data

C9H11N3O2S	F(000) = 472
Mr = 225.27	Dx = 1.496 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.3058 (2) Å	Cell parameters from 3917 reflections
b = 6.0582 (1) Å	θ = 3.3–29.8°
c = 22.6041 (6) Å	µ = 0.31 mm−1
β = 91.100 (2)°	T = 100 K
V = 1000.27 (4) Å3	Block, colourless
Z = 4	0.48 × 0.19 × 0.14 mm

Data collection

Bruker APEXII CCD diffractometer	2302 independent reflections
Radiation source: sealed tube	1950 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.027
φ and ω scans	θmax = 27.5°, θmin = 1.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.866, Tmax = 0.957	k = −7→7
9696 measured reflections	l = −29→24

Refinement

Refinement on F2	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.035	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.086	w = 1/[σ2(Fo2) + (0.0336P)2 + 0.7405P] where P = (Fo2 + 2Fc2)/3
S = 1.06	(Δ/σ)max = 0.001
2302 reflections	Δρmax = 0.30 e Å−3
153 parameters	Δρmin = −0.31 e Å−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

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

	x	y	z	Uiso*/Ueq
S1	0.15271 (5)	1.11056 (7)	1.14702 (2)	0.01707 (12)
O1	0.33247 (16)	0.2527 (2)	1.00557 (5)	0.0174 (3)
H1o	0.301 (3)	0.362 (4)	1.0247 (11)	0.044 (7)*
O2	0.45517 (16)	0.0527 (2)	0.80619 (5)	0.0204 (3)
H2o	0.541 (3)	−0.033 (4)	0.8232 (11)	0.051 (7)*
N1	0.15573 (18)	0.6695 (2)	1.14178 (6)	0.0148 (3)
H1n	0.153 (3)	0.557 (3)	1.1220 (9)	0.019 (5)*
N2	0.15295 (18)	0.8552 (2)	1.05291 (6)	0.0152 (3)
H2n	0.183 (3)	0.984 (4)	1.0359 (9)	0.029 (5)*
N3	0.19726 (17)	0.6617 (2)	1.02301 (6)	0.0139 (3)
C1	0.1544 (2)	0.8599 (3)	1.11312 (7)	0.0135 (3)
C2	0.1526 (2)	0.6471 (3)	1.20604 (7)	0.0197 (4)
H2A	0.2699	0.6968	1.2231	0.030*
H2B	0.1326	0.4920	1.2164	0.030*
H2C	0.0534	0.7374	1.2217	0.030*
C3	0.1997 (2)	0.6841 (3)	0.96619 (7)	0.0141 (3)
H3	0.1592	0.8197	0.9494	0.017*
C4	0.2616 (2)	0.5119 (3)	0.92679 (7)	0.0137 (3)
C5	0.3302 (2)	0.3078 (3)	0.94674 (7)	0.0135 (3)
C6	0.3978 (2)	0.1534 (3)	0.90734 (7)	0.0154 (3)
H6	0.4461	0.0173	0.9214	0.019*
C7	0.3941 (2)	0.1999 (3)	0.84699 (7)	0.0157 (3)
C8	0.3264 (2)	0.4006 (3)	0.82584 (7)	0.0177 (3)
H8	0.3239	0.4312	0.7846	0.021*
C9	0.2630 (2)	0.5540 (3)	0.86554 (7)	0.0168 (3)
H9	0.2192	0.6920	0.8512	0.020*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
S1	0.0239 (2)	0.0115 (2)	0.0158 (2)	0.00296 (15)	0.00059 (15)	−0.00209 (15)
O1	0.0274 (6)	0.0135 (6)	0.0114 (6)	0.0017 (5)	0.0029 (5)	0.0007 (5)
O2	0.0214 (6)	0.0243 (7)	0.0154 (6)	0.0041 (5)	0.0010 (5)	−0.0062 (5)
N1	0.0223 (7)	0.0099 (7)	0.0120 (7)	−0.0017 (5)	0.0015 (5)	−0.0019 (6)
N2	0.0215 (7)	0.0103 (7)	0.0137 (7)	0.0012 (5)	0.0019 (5)	−0.0007 (5)
N3	0.0163 (6)	0.0116 (6)	0.0139 (7)	−0.0005 (5)	0.0011 (5)	−0.0023 (5)
C1	0.0119 (7)	0.0145 (8)	0.0141 (8)	0.0005 (6)	0.0004 (6)	−0.0009 (6)
C2	0.0279 (9)	0.0177 (8)	0.0137 (8)	−0.0017 (7)	0.0020 (6)	0.0019 (7)
C3	0.0144 (7)	0.0125 (7)	0.0153 (8)	−0.0008 (6)	0.0001 (6)	0.0006 (6)
C4	0.0140 (7)	0.0143 (8)	0.0129 (7)	−0.0016 (6)	0.0011 (6)	0.0002 (6)
C5	0.0145 (7)	0.0150 (8)	0.0110 (7)	−0.0036 (6)	0.0004 (5)	0.0005 (6)
C6	0.0150 (7)	0.0136 (8)	0.0177 (8)	−0.0006 (6)	0.0018 (6)	0.0009 (6)
C7	0.0139 (7)	0.0180 (8)	0.0152 (8)	−0.0016 (6)	0.0025 (6)	−0.0043 (6)
C8	0.0184 (7)	0.0240 (9)	0.0106 (7)	0.0022 (6)	0.0006 (6)	0.0008 (7)
C9	0.0163 (7)	0.0187 (8)	0.0153 (8)	0.0008 (6)	0.0005 (6)	0.0027 (7)

Geometric parameters (Å, º)

S1—C1	1.7011 (16)	C2—H2B	0.9800
O1—C5	1.3707 (19)	C2—H2C	0.9800
O1—H1o	0.83 (3)	C3—C4	1.449 (2)
O2—C7	1.3640 (19)	C3—H3	0.9500
O2—H2o	0.90 (3)	C4—C5	1.405 (2)
N1—C1	1.323 (2)	C4—C9	1.408 (2)
N1—C2	1.459 (2)	C5—C6	1.389 (2)
N1—H1n	0.81 (2)	C6—C7	1.393 (2)
N2—C1	1.361 (2)	C6—H6	0.9500
N2—N3	1.3945 (18)	C7—C8	1.394 (2)
N2—H2n	0.90 (2)	C8—C9	1.378 (2)
N3—C3	1.292 (2)	C8—H8	0.9500
C2—H2A	0.9800	C9—H9	0.9500
C5—O1—H1o	108.3 (17)	C4—C3—H3	118.5
C7—O2—H2o	108.9 (16)	C5—C4—C9	117.76 (14)
C1—N1—C2	124.63 (14)	C5—C4—C3	123.32 (14)
C1—N1—H1n	117.4 (14)	C9—C4—C3	118.82 (14)
C2—N1—H1n	117.9 (14)	O1—C5—C6	117.41 (14)
C1—N2—N3	120.33 (13)	O1—C5—C4	121.55 (14)
C1—N2—H2n	114.2 (13)	C6—C5—C4	121.04 (14)
N3—N2—H2n	117.6 (13)	C5—C6—C7	119.46 (15)
C3—N3—N2	113.67 (13)	C5—C6—H6	120.3
N1—C1—N2	118.11 (14)	C7—C6—H6	120.3
N1—C1—S1	123.91 (12)	O2—C7—C6	122.00 (15)
N2—C1—S1	117.98 (12)	O2—C7—C8	117.19 (14)
N1—C2—H2A	109.5	C6—C7—C8	120.81 (14)
N1—C2—H2B	109.5	C9—C8—C7	119.10 (15)
H2A—C2—H2B	109.5	C9—C8—H8	120.4
N1—C2—H2C	109.5	C7—C8—H8	120.4
H2A—C2—H2C	109.5	C8—C9—C4	121.80 (15)
H2B—C2—H2C	109.5	C8—C9—H9	119.1
N3—C3—C4	123.08 (15)	C4—C9—H9	119.1
N3—C3—H3	118.5
C1—N2—N3—C3	−176.54 (14)	C3—C4—C5—C6	−176.13 (14)
C2—N1—C1—N2	−178.35 (14)	O1—C5—C6—C7	178.45 (13)
C2—N1—C1—S1	1.2 (2)	C4—C5—C6—C7	−1.3 (2)
N3—N2—C1—N1	−15.6 (2)	C5—C6—C7—O2	−178.64 (14)
N3—N2—C1—S1	164.83 (11)	C5—C6—C7—C8	1.1 (2)
N2—N3—C3—C4	173.05 (13)	O2—C7—C8—C9	179.92 (14)
N3—C3—C4—C5	−2.2 (2)	C6—C7—C8—C9	0.2 (2)
N3—C3—C4—C9	−178.56 (14)	C7—C8—C9—C4	−1.3 (2)
C9—C4—C5—O1	−179.49 (14)	C5—C4—C9—C8	1.0 (2)
C3—C4—C5—O1	4.1 (2)	C3—C4—C9—C8	177.60 (14)
C9—C4—C5—C6	0.3 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1o···N3	0.83 (2)	1.97 (2)	2.6992 (17)	147 (2)
N1—H1n···N3	0.815 (19)	2.35 (2)	2.7080 (19)	107.1 (16)
O2—H2o···S1i	0.90 (2)	2.37 (2)	3.1918 (12)	152 (2)
N1—H1n···S1ii	0.815 (19)	2.763 (18)	3.3883 (13)	134.9 (17)
N2—H2n···O1iii	0.90 (2)	2.08 (2)	2.9527 (17)	162 (2)

Symmetry codes: (i) −x+1, −y+1, −z+2; (ii) x, y−1, z; (iii) x, y+1, z.