Crystal structure of N-(4-hy­droxy­benz­yl)acetone thio­semicarbazone

Argibay-Otero, S.; Vázquez-López, E.M.

doi:10.1107/S2056989017012129

research communications

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 73| Part 9| September 2017| Pages 1382-1384

https://doi.org/10.1107/S2056989017012129

Open

access

Crystal structure of N-(4-hydroxybenzyl)acetone thiosemicarbazone

Saray Argibay-Otero ^a and Ezequiel M. Vázquez-López ^a ^*

^aDepartamento de Química Inorgánica, Facultade de Química, Instituto de Investigación Sanitaria Galicia Sur – Universidade de Vigo, Campus Universitario, E-36310 Vigo, Galicia, Spain
^*Correspondence e-mail: ezequiel@uvigo.es

Edited by G. Smith, Queensland University of Technology, Australia (Received 27 July 2017; accepted 22 August 2017; online 25 August 2017)

The structure of the title compound, C₁₁H₁₅N₃OS, shows the flexibility due to the methylene group at the thioamide N atom in the side chain, resulting in the molecule being non-planar. The dihedral angle between the plane of the benzene ring and that defined by the atoms of the thiosemicarbazide arm is 79.847 (4)°. In the crystal, the donor–acceptor hydrogen-bond character of the –OH group dominates the intermolecular associations, acting as a donor in an O—H⋯S hydrogen bond, as well as being a double acceptor in a centrosymmetric cyclic bridging N—H⋯O,O′ interaction [graph set R₂²(4)]. The result is a one-dimensional duplex chain structure, extending along [111]. The usual N—H⋯S hydrogen-bonding association common in thiosemicarbazone crystal structures is not observed.

Keywords: crystal structure; thiosemicarbazone; thiourea; hydrogen bonding.

CCDC reference: 1570200

1. Chemical context

Thiosemicarbazones (TSCs) are an interesting group of compounds because they show diverse biological properties (Serda et al., 2012 ) and pharmacological activities (Lukmantara et al., 2013 ). They can be easily functionalized to yield different supramolecular arrays through intermolecular hydrogen-bonding interactions (Nuñez-Montenegro et al., 2017 ), by selection of suitable aldehyde or ketone reagents. In addition, metal coordination may be used to orient some of their substituents to optimize the interaction with biomolecules (e.g. see Nuñez-Montenegro et al., 2014 ). In the present paper, we describe the synthesis and crystal structure of a TSC derivative (Figs. 1), namely N-(4-hydroxybenzyl)acetone thiosemicarbazone (acTSC), having a 4-hydroxybenzyl substituent at the thioamide N atom (N1), in which the –CH₂– group provides more flexibility to establish intermolecular associations.

Figure 1
Reaction scheme for the synthesis of acTSC.

2. Structural commentary

In the acTSC molecule (Fig. 2), the bond lengths (S1=C1 and C10=N3) and angles in the thiosemicarbazide arm are similar to those observed in other thiosemicarbazones, suggesting that the thione form is predominant. This arm is almost planar, probably due to some π-delocation (r.m.s. deviation of 0.0516 Å for the plane defined by atoms S1/C1/N1/N2/N3). Nevertheless, the ethylene group at N1 allows an almost orthogonal orientation relative to the phenolic substituent group, with a dihedral angle between the two planes of 79.847 (4)°. The interatomic distance N1⋯N3 interaction [2.6074 (18) Å] suggests some kind of intramolecular interaction.

Figure 2
The molecular structure of acTSC, with displacement ellipsoids drawn at the 40% probability level.

3. Supramolecular features

The association of the molecules is strongly affected by the donor–acceptor character of the –OH group, while the usual N—H⋯S hydrogen bonds observed in most TSC structures (Nuñez-Montenegro et al., 2017; Pino-Cuevas et al., 2014 ) are absent. The phenolic –OH group forms an intermolecular hydrogen bond with a S-atom acceptor (O—H0⋯S1ⁱⁱⁱ; Table 1), while the N2—H group establishes two different hydrogen-bonding interactions with different phenolic O-atom acceptors. The shortest of these is N2—H2⋯Oⁱ (Table 1), which generates a centrosymmetric cyclic R₂²(4) ring-motif association (Etter, 1990 ) and also forms a conjoined cyclic R₂²(6) association via an O—H⋯S interaction (see Fig. 3). The second of the three-centre hydrogen-bonding interactions (N2—H2⋯Oⁱⁱ) extends the structure into one-dimensional duplex chains along [111] (Fig. 3).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2⋯Oⁱ	0.848 (17)	2.292 (17)	2.9955 (15)	140.6 (14)
N2—H2⋯Oⁱⁱ	0.848 (17)	2.434 (16)	3.1333 (15)	140.3 (14)
O—H0⋯S1ⁱⁱⁱ	0.857 (19)	2.299 (19)	3.1349 (10)	165.2 (16)
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) x-1, y-1, z-1; (iii) x+1, y+1, z+1.

Figure 3
Intermolecular hydrogen-bonding associations between molecules in the crystal structure of acTSC, shown as dashed lines.

4. Database survey

For related structures of thiosemicarbazones derived from acetone, see: Yamin et al. (2014 ); Basu & Das (2011 ); Venkatraman et al. (2005 ); Jian et al. (2005 ). For the metal-coordination properties of thiosemicarbazones, see: Paterson & Donnelly (2011 ); Casas et al. (2000 ). For acetone derivatives, see, for example, Su et al. (2013 ); Nuñez-Montenegro et al. (2014); Swesi et al. (2006 ); Paek et al. (1997 ).

5. Synthesis and crystallization

The reaction scheme for the synthesis of the title compound is shown in Fig. 1. The primary amine 4-hydroxybenzylamine was converted to the corresponding isothiocyanate by reaction with thiophosgene (Sharma, 1978 ). This isothiocyanate was treated with hydrazide to form the thiosemicarbazide, as described previously (Reis et al., 2011 ). Finally, this compound was reacted with acetone in order to synthesize the desired thiosemicarbazone. In a typical synthesis, 3.4 g (0.017 mol) of thiosemicarbazide was dissolved in acetone (20 ml) and heated to 60°C for 20 min (Fig. 1). This solution was concentrated and the resultant residue was purified using a silica column (AcOEt–hexane 30%). This solution was vacuum dried giving 1.96 g of acTSC. The solution was also used to obtain single crystals by slow evaporation (yield 48%; m.p. 165°C). C₁₁H₁₅N₃OS requires: C 55.7, H 6.4, N 17.7%; found C 55.8, H 7.1,N 16.9%. MS–ESI [m/z (%)]: 238 (100) [M + H]⁺. IR (ATR, ν/cm⁻¹): 3241 (b) ν(NH, OH); 1536 (w), 1508 (s) ν(C=N); 784 (w) ν(C=S). ¹H NMR (DMSO-d₆): 9.95 (s, 1H, N2H), 9.26 (s, 1H, OH), 8.46 (t, ³J_H-NH = 6.2Hz, 1H, N1H), 7.15 (d, ³J_H-H = 8.5Hz, 2H, C5H, C9H), 6.70 (d, ³J_H-H = 8.5Hz, 2H, C6H, C8H), 4.65 (d, ³J_H-H = 6.2Hz, 2H, C3H), 1.92 (d, ³J_H-H = 8.5Hz, 6H, C11H, C12H).

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. Interactive H atoms on O and N atoms were located in difference Fourier analyses and were allowed to freely refine, with U_iso(H) = 1.2U_eq(O,N) and riding. Other H atoms were included at calculated sites and allowed to ride, with U_iso(H) = 1.2U_eq(aromatic and methylene C) or 1.5U_eq(methyl C).

Table 2
Experimental details

Crystal data
Chemical formula	C₁₁H₁₅N₃OS
M_r	237.32
Crystal system, space group	Triclinic, P $[\overline{1}]$
Temperature (K)	100
a, b, c (Å)	8.2799 (8), 8.9169 (9), 9.7451 (10)
α, β, γ (°)	104.597 (3), 112.569 (3), 105.220 (3)
V (Å³)	588.7 (1)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	0.26
Crystal size (mm)	0.18 × 0.11 × 0.11

Data collection
Diffractometer	Bruker D8 Venture Photon 100 CMOS
Absorption correction	Multi-scan (SADABS; Bruker, 2014 )
T_min, T_max	0.638, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	17083, 2911, 2562
R_int	0.043
(sin θ/λ)_max (Å⁻¹)	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.032, 0.082, 1.00
No. of reflections	2911
No. of parameters	156
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.29, −0.28
Computer programs: APEX3 (Bruker, 2014), SAINT (Bruker, 2014), SHELXS2013 (Sheldrick, 2015a ), SHELXL2013 (Sheldrick, 2015b ) and Mercury (Bruno et al., 2002 ).

Supporting information

CCDC reference: 1570200

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2056989017012129/zs2385sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017012129/zs2385Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX3 (Bruker, 2014); cell refinement: SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2015b); molecular graphics: Mercury (Bruno et al., 2002); software used to prepare material for publication: SHELXL2013 (Sheldrick, 2015b).

(I) top

Crystal data top

C₁₁H₁₅N₃OS	F(000) = 252
M_r = 237.32	D_x = 1.339 Mg m⁻³
Triclinic, P1	Melting point: 438 K
a = 8.2799 (8) Å	Mo Kα radiation, λ = 0.71073 Å
b = 8.9169 (9) Å	Cell parameters from 9917 reflections
c = 9.7451 (10) Å	θ = 2.5–28.3°
α = 104.597 (3)°	µ = 0.26 mm⁻¹
β = 112.569 (3)°	T = 100 K
γ = 105.220 (3)°	Prism, colourless
V = 588.7 (1) Å³	0.18 × 0.11 × 0.11 mm
Z = 2

Data collection top

Bruker D8 Venture Photon 100 CMOS diffractometer	2562 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.043
Absorption correction: multi-scan (SADABS; Bruker, 2014)	θ_max = 28.3°, θ_min = 2.5°
T_min = 0.638, T_max = 0.746	h = −11→11
17083 measured reflections	k = −11→11
2911 independent reflections	l = −12→13

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.032	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.082	w = 1/[σ²(F_o²) + (0.0325P)² + 0.3538P] where P = (F_o² + 2F_c²)/3
S = 1.00	(Δ/σ)_max < 0.001
2911 reflections	Δρ_max = 0.29 e Å⁻³
156 parameters	Δρ_min = −0.28 e Å⁻³

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
C12	0.5032 (2)	−0.1953 (2)	0.3563 (2)	0.0345 (4)
H12A	0.6301	−0.1042	0.4309	0.052*
H12B	0.5165	−0.2971	0.3036	0.052*
H12C	0.4356	−0.2199	0.4166	0.052*
C11	0.1912 (2)	−0.26338 (16)	0.10998 (17)	0.0243 (3)
H11A	0.1070	−0.2506	0.1562	0.036*
H11B	0.1842	−0.3793	0.0828	0.036*
H11C	0.1508	−0.2401	0.0118	0.036*
S1	0.33739 (4)	0.28903 (4)	0.00401 (4)	0.02014 (10)
O	0.96910 (14)	0.95385 (12)	0.83590 (11)	0.0206 (2)
H0	1.063 (3)	1.046 (2)	0.864 (2)	0.031*
N2	0.37419 (16)	0.05734 (13)	0.12372 (13)	0.0170 (2)
H2	0.254 (2)	0.024 (2)	0.0853 (19)	0.020*
N1	0.65479 (15)	0.27673 (13)	0.21157 (13)	0.0163 (2)
H1	0.701 (2)	0.225 (2)	0.2663 (19)	0.020*
N3	0.47907 (15)	0.00499 (14)	0.23774 (13)	0.0194 (2)
C6	0.79084 (18)	0.67223 (16)	0.64146 (15)	0.0173 (2)
H6	0.7308	0.6484	0.7038	0.021*
C3	0.77639 (18)	0.44581 (15)	0.24342 (15)	0.0171 (2)
H3A	0.7100	0.4789	0.1551	0.021*
H3B	0.8951	0.4438	0.2427	0.021*
C1	0.46524 (17)	0.20611 (15)	0.12097 (14)	0.0147 (2)
C4	0.82883 (17)	0.57817 (15)	0.40388 (14)	0.0148 (2)
C7	0.92864 (17)	0.83296 (15)	0.69457 (14)	0.0158 (2)
C9	0.96926 (17)	0.73918 (15)	0.46107 (15)	0.0170 (2)
H9	1.0319	0.7622	0.4003	0.020*
C8	1.01956 (17)	0.86683 (15)	0.60508 (15)	0.0164 (2)
H8	1.1150	0.9760	0.6419	0.020*
C5	0.74164 (17)	0.54680 (15)	0.49646 (15)	0.0162 (2)
H5	0.6466	0.4376	0.4600	0.019*
C10	0.39253 (19)	−0.14134 (17)	0.23078 (16)	0.0197 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C12	0.0274 (8)	0.0421 (9)	0.0502 (10)	0.0188 (7)	0.0187 (7)	0.0374 (8)
C11	0.0297 (7)	0.0153 (6)	0.0263 (7)	0.0065 (5)	0.0131 (6)	0.0090 (5)
S1	0.01646 (16)	0.01708 (15)	0.02248 (17)	0.00497 (12)	0.00379 (13)	0.01202 (12)
O	0.0182 (5)	0.0184 (4)	0.0173 (4)	0.0022 (4)	0.0071 (4)	0.0030 (4)
N2	0.0138 (5)	0.0164 (5)	0.0197 (5)	0.0056 (4)	0.0053 (4)	0.0104 (4)
N1	0.0152 (5)	0.0145 (5)	0.0182 (5)	0.0059 (4)	0.0059 (4)	0.0083 (4)
N3	0.0174 (5)	0.0228 (5)	0.0238 (6)	0.0108 (4)	0.0097 (5)	0.0157 (5)
C6	0.0154 (6)	0.0201 (6)	0.0178 (6)	0.0059 (5)	0.0085 (5)	0.0101 (5)
C3	0.0151 (6)	0.0164 (6)	0.0187 (6)	0.0042 (5)	0.0081 (5)	0.0076 (5)
C1	0.0163 (6)	0.0135 (5)	0.0139 (5)	0.0060 (5)	0.0075 (5)	0.0046 (4)
C4	0.0131 (5)	0.0158 (5)	0.0161 (6)	0.0072 (5)	0.0055 (5)	0.0082 (5)
C7	0.0134 (5)	0.0169 (6)	0.0144 (6)	0.0067 (5)	0.0036 (5)	0.0065 (4)
C9	0.0154 (6)	0.0182 (6)	0.0202 (6)	0.0065 (5)	0.0094 (5)	0.0110 (5)
C8	0.0131 (5)	0.0146 (5)	0.0194 (6)	0.0041 (4)	0.0056 (5)	0.0086 (5)
C5	0.0131 (5)	0.0154 (5)	0.0186 (6)	0.0042 (4)	0.0060 (5)	0.0087 (5)
C10	0.0213 (6)	0.0225 (6)	0.0263 (7)	0.0131 (5)	0.0155 (5)	0.0152 (5)

Geometric parameters (Å, º) top

S1—C1	1.6959 (14)	C8—C9	1.3914 (18)
O—C7	1.3708 (16)	C10—C11	1.498 (2)
O—H0	0.86 (2)	C10—C12	1.495 (2)
N1—C3	1.4527 (19)	C3—H3A	0.9900
N1—C1	1.3328 (19)	C3—H3B	0.9900
N2—N3	1.3929 (17)	C5—H5	0.9500
N2—C1	1.3554 (19)	C6—H6	0.9500
N3—C10	1.284 (2)	C8—H8	0.9500
N1—H1	0.839 (18)	C9—H9	0.9500
N2—H2	0.849 (18)	C11—H11A	0.9800
C3—C4	1.5186 (18)	C11—H11B	0.9800
C4—C5	1.391 (2)	C11—H11C	0.9800
C4—C9	1.395 (2)	C12—H12A	0.9800
C5—C6	1.3914 (19)	C12—H12B	0.9800
C6—C7	1.392 (2)	C12—H12C	0.9800
C7—C8	1.391 (2)

C7—O—H0	111.1 (13)	N1—C3—H3B	109.00
C1—N1—C3	124.73 (12)	C4—C3—H3A	109.00
N2—N3—C10	116.82 (12)	C4—C3—H3B	109.00
S1—C1—N1	124.19 (11)	H3A—C3—H3B	108.00
S1—C1—N2	119.75 (11)	C4—C5—H5	119.00
C1—N1—H1	115.1 (12)	C6—C5—H5	119.00
C3—N1—H1	119.1 (12)	C5—C6—H6	120.00
N1—C1—N2	116.05 (12)	C7—C6—H6	120.00
N3—N2—H2	120.9 (12)	C7—C8—H8	120.00
C1—N2—H2	116.2 (13)	C9—C8—H8	120.00
N1—C3—C4	113.39 (12)	C4—C9—H9	119.00
C3—C4—C5	122.91 (12)	C8—C9—H9	119.00
C5—C4—C9	118.17 (12)	C10—C11—H11A	109.00
C3—C4—C9	118.92 (12)	C10—C11—H11B	109.00
C4—C5—C6	121.31 (13)	C10—C11—H11C	109.00
C5—C6—C7	119.54 (13)	H11A—C11—H11B	109.00
O—C7—C6	117.57 (13)	H11A—C11—H11C	109.00
C6—C7—C8	120.21 (12)	H11B—C11—H11C	109.00
O—C7—C8	122.21 (12)	C10—C12—H12A	109.00
C7—C8—C9	119.30 (13)	C10—C12—H12B	109.00
C4—C9—C8	121.46 (13)	C10—C12—H12C	109.00
N3—C10—C12	116.82 (14)	H12A—C12—H12B	109.00
C11—C10—C12	116.61 (14)	H12A—C12—H12C	109.00
N3—C10—C11	126.57 (13)	H12B—C12—H12C	109.00
N1—C3—H3A	109.00

C3—N1—C1—S1	10.03 (19)	C3—C4—C9—C8	178.25 (13)
C3—N1—C1—N2	−171.02 (12)	C3—C4—C5—C6	−178.75 (14)
C1—N1—C3—C4	97.14 (15)	C9—C4—C5—C6	0.6 (2)
C1—N2—N3—C10	−175.62 (14)	C5—C4—C9—C8	−1.1 (2)
N3—N2—C1—S1	−170.98 (10)	C4—C5—C6—C7	0.7 (2)
N3—N2—C1—N1	10.02 (19)	C5—C6—C7—C8	−1.4 (2)
N2—N3—C10—C12	−178.18 (13)	C5—C6—C7—O	178.34 (13)
N2—N3—C10—C11	1.5 (2)	O—C7—C8—C9	−178.83 (13)
N1—C3—C4—C9	169.60 (13)	C6—C7—C8—C9	0.9 (2)
N1—C3—C4—C5	−11.0 (2)	C7—C8—C9—C4	0.4 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···Oⁱ	0.848 (17)	2.292 (17)	2.9955 (15)	140.6 (14)
N2—H2···Oⁱⁱ	0.848 (17)	2.434 (16)	3.1333 (15)	140.3 (14)
O—H0···S1ⁱⁱⁱ	0.857 (19)	2.299 (19)	3.1349 (10)	165.2 (16)

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

Funding information

Funding for this research was provided by: Ministry of Economy, Industry and Competitiveness (Spain) and European Regional Development Fund (EU) (CTQ2015-71211-REDT and CTQ2015-7091-R).

References

Basu, A. & Das, G. (2011). Dalton Trans. 40, 2837–2843. Web of Science CSD CrossRef CAS PubMed Google Scholar
Bruker (2014). APEX3, SAINT and SADABS, Bruker ASX Inc., Madison, Wisconsin, USA. Google Scholar
Bruno, I. J., Cole, J. C., Edgington, P. R., Kessler, M., Macrae, C. F., McCabe, P., Pearson, J. & Taylor, R. (2002). Acta Cryst. B58, 389–397. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Casas, J. S., García-Tasende, M. S. & Sordo, J. (2000). Coord. Chem. Rev. 209, 197–261. Web of Science CrossRef CAS Google Scholar
Etter, M. C. (1990). Acc. Chem. Res. 23, 120–126. CrossRef CAS Web of Science Google Scholar
Jian, F.-F., Bai, Z.-S., Xiao, H.-L. & Li, K. (2005). Acta Cryst. E61, o653–o654. Web of Science CSD CrossRef IUCr Journals Google Scholar
Lukmantara, A. Y., Kalinowski, D. S., Kumar, N. & Richardson, D. R. (2013). Bioorg. Med. Chem. Lett. 23, 967–974. Web of Science CSD CrossRef CAS PubMed Google Scholar
Nuñez-Montenegro, A., Argibay-Otero, S., Carballo, R., Graña, A. & Vázquez-López, E. M. (2017). Cryst. Growth Des. 17, 3338–3349. Google Scholar
Nuñez-Montenegro, A., Carballo, R. & Vázquez-López, E. M. (2014). J. Inorg. Biochem. 140, 53–63. PubMed Google Scholar
Paek, C., Kang, S. O., Ko, J. & Carroll, P. J. (1997). Organometallics, 16, 2110–2115. CSD CrossRef CAS Google Scholar
Paterson, B. M. & Donnelly, P. S. (2011). Chem. Soc. Rev. 40, 3005–3018. Web of Science CrossRef CAS PubMed Google Scholar
Pino-Cuevas, A., Carballo, R. & Vázquez-López, E. M. (2014). Acta Cryst. E70, o926. CSD CrossRef IUCr Journals Google Scholar
Reis, C. M., Pereira, D. S., Paiva, R. O., Kneipp, L. F. & Echevarria, A. (2011). Molecules, 16, 10668–10684. CrossRef PubMed Google Scholar
Serda, M., Mrozek-Wilczkiewicz, A., Jampilek, J., Pesko, M., Kralova, K., Vejsova, M., Musiol, R., Ratuszna, A. & Polanski, J. (2012). Molecules, 17, 13483–13502. Web of Science CrossRef CAS PubMed Google Scholar
Sharma, S. (1978). Synthesis, pp. 803–820. CrossRef Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Su, W., Quia, Q., Li, P., Lei, X., Xiao, Q., Huan, S., Huang, C. & Cui, J. (2013). Inorg. Chem. 52, 12440–12449. CSD CrossRef CAS PubMed Google Scholar
Swesi, A. T., Farina, Y., Venkatraman, R. & Ng, S. W. (2006). Acta Cryst. E62, m3020–m3021. CSD CrossRef IUCr Journals Google Scholar
Venkatraman, R., Swesi, A. T. & Yamin, B. M. (2005). Acta Cryst. E61, o3914–o3916. Web of Science CSD CrossRef IUCr Journals Google Scholar
Yamin, B. M., Rodis, M. L. & Chee, D. N. B. A. (2014). Acta Cryst. E70, o1109. CSD CrossRef IUCr Journals Google Scholar