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Acta Cryst. (2011). E67, o1148    [ doi:10.1107/S1600536811013377 ]

3-Cyclohexyl-1-(3,5-dinitrobenzoyl)thiourea

S. Saeed, N. Rashid, M. Sher, S. W. Ng and E. R. T. Tiekink

Abstract top

The structure of the title thiourea derivative, C14H16N4O5S, features an almost planar central C2N2OS fragment (r.m.s. deviation = 0.005 Å), an arrangement stabilized by an intramolecular N-H...O hydrogen bond. The terminal rings are twisted out of this plane, the dihedral angle formed with the benzene ring being 33.22 (10)°. The cyclohexyl ring is disordered, with two orientations (50:50) being resolved. The mean plane passing through the atoms of each disordered component forms dihedral angles of 65.7 (2) and 82.4 (3)° with the central plane. Centrosymmetric dimers mediated by an eight-membered {...HNC=S}2 synthon occur in the crystal.

Comment top

Continuing structural studies (Gunasekaran et al. 2010; Saeed et al. 2010; Dzulkifli et al., 2011) of thiourea derivatives are motivated by their biological potential (Venkatachalam et al., 2004; Saeed et al., 2011) and led to the investigation of the title compound, (I).

The molecular structure of (I), Fig. 1, is highly twisted with dihedral angles formed between the central chromophore (r.m.s. = 0.0054 Å for C7,C8,N1,N2,O1 & S1) and the benzene ring being 33.22 (10) °. Two orientations of equal weight were found for the cyclohexyl ring, each with a chair conformation, and these make angles of 65.74 (24) and 82.42 (30) °, respectively, with the central plane. The N—H atoms are anti as are the S and O atoms. As a consequence, the N1—H atom forms an intramolecular hydrogen bond with the carbonyl-O1 atom to close a pseudo six-membered ring, Table 1; there are two values cited owing to the disorder in the molecule. The nitro groups are effectively co-planar with the benzene ring to which they are bonded as seen in the values of the O2—N3—C11—C10 and O4—N4—C13—C12 torsion angles of 1.2 (5) and -7.0 (5) °, respectively.

The most prominent feature of the crystal packing is the formation of centrosymmetric eight-membered {···HNC═S}2 synthon leading to dimeric aggregates, Fig. 2 and Table 1.

Related literature top

For the biological activity of thiourea derivatives, see: Venkatachalam et al. (2004); Saeed et al. (2011). For related thiourea structures, see: Gunasekaran et al. (2010); Saeed et al. (2010); Dzulkifli et al. (2011).

Experimental top

A solution of 3,5-dinitrobenzoyl chloride (0.01 mol) in anhydrous acetone (75 ml) and 3% tetrabutylammonium bromide (TBAB), as a phase-transfer catalyst (PTC), in anhydrous acetone was added drop-wise to a suspension of dry potassium thiocyanate (0.01 mol) in acetone (50 ml). The reaction mixture was refluxed for 50 min. After cooling to room temperature, a solution of cyclohexylamine (0.01 mol) in anhydrous acetone (25 ml) was added drop-wise and the resulting mixture refluxed for 3 h. Hydrochloric acid (0.1 N, 300 ml) was added and the solution was filtered. The solid product was washed with water and purified by re-crystallization from ethanol; Yield: 1.50 g (88%) and M.pt. 409 K. IR (KBr, cm-1): 3215 ν(NH), 1673 (C=O), 1527 (benzene ring), 1138 ν(C═S). Anal. Calcd. for C14H16N4O5S: C, 47.72; H, 4.58; N, 15.90; S, 9.10%. Found: C, 47.51; H, 4.75; N, 15.88; S, 9.11%.

Refinement top

Carbon-bound H-atoms were placed in calculated positions [C—H 0.93 to 0.97 Å, Uiso(H) 1.2Ueq(C)] and were included in the refinement in the riding model approximation. The two amino H-atoms were similarly placed [N–H 0.88 Å, Uiso(H) 1.2Ueq(N)]. The cyclohexyl ring is disordered over two positions; the disorder could not be refined, and was assumed to be a 1:1 type of disorder. The 1,2-related C–C distances were restrained to 1.54±0.01 Å and the 1,3-related ones to 2.51±0.01 Å. The pair of N–Ccyclohexyl and N–C'cyclohexyl distances were restrained to within 0.01 Å of each other.

Computing details top

Data collection: CrysAlis PRO (Agilent, 2010); cell refinement: CrysAlis PRO (Agilent, 2010); data reduction: CrysAlis PRO (Agilent, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) showing displacement ellipsoids at the 35% probability level. Only one orientation of the disordered cyclohexyl ring is shown.
[Figure 2] Fig. 2. Supramolecular dimer in (I) mediated by N—H···S hydrogen bonding shown as orange dashed lines. Only one orientation of the disordered cyclohexyl ring is shown.
3-Cyclohexyl-1-(3,5-dinitrobenzoyl)thiourea top
Crystal data top
C14H16N4O5SF(000) = 736
Mr = 352.37Dx = 1.430 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 2522 reflections
a = 12.3404 (7) Åθ = 2.6–29.2°
b = 9.0506 (5) ŵ = 0.23 mm−1
c = 14.6534 (6) ÅT = 295 K
β = 90.385 (5)°Prism, colorless
V = 1636.57 (15) Å30.20 × 0.15 × 0.10 mm
Z = 4
Data collection top
Agilent Technologies SuperNova Dual
diffractometer with an Atlas detector		3649 independent reflections
Radiation source: SuperNova (Mo) X-ray Source1948 reflections with I > 2σ(I)
MirrorRint = 0.024
Detector resolution: 10.4041 pixels mm-1θmax = 27.5°, θmin = 2.7°
ω scansh = −11→16
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2010)		k = −11→9
Tmin = 0.955, Tmax = 0.977l = −19→18
7954 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.061Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.211H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.0901P)2 + 0.5204P]
where P = (Fo2 + 2Fc2)/3
3649 reflections(Δ/σ)max = 0.001
271 parametersΔρmax = 0.22 e Å−3
25 restraintsΔρmin = −0.28 e Å−3
Crystal data top
C14H16N4O5SV = 1636.57 (15) Å3
Mr = 352.37Z = 4
Monoclinic, P21/cMo Kα radiation
a = 12.3404 (7) ŵ = 0.23 mm−1
b = 9.0506 (5) ÅT = 295 K
c = 14.6534 (6) Å0.20 × 0.15 × 0.10 mm
β = 90.385 (5)°
Data collection top
Agilent Technologies SuperNova Dual
diffractometer with an Atlas detector		3649 independent reflections
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2010)		1948 reflections with I > 2σ(I)
Tmin = 0.955, Tmax = 0.977Rint = 0.024
7954 measured reflectionsθmax = 27.5°
Refinement top
R[F2 > 2σ(F2)] = 0.061H-atom parameters constrained
wR(F2) = 0.211Δρmax = 0.22 e Å−3
S = 1.01Δρmin = −0.28 e Å−3
3649 reflectionsAbsolute structure: ?
271 parametersFlack parameter: ?
25 restraintsRogers parameter: ?
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
S10.41365 (9)0.64167 (12)0.59283 (6)0.0914 (4)
O10.2058 (2)0.5972 (4)0.33847 (18)0.1069 (9)
O20.1940 (3)0.2554 (4)0.0798 (2)0.1410 (13)
O30.3315 (3)0.2306 (4)−0.0052 (3)0.1351 (13)
O40.6723 (3)0.4548 (4)0.0872 (2)0.1237 (11)
O50.6733 (2)0.6067 (4)0.2004 (2)0.1140 (10)
N10.2226 (2)0.6699 (3)0.5124 (2)0.0864 (9)
H10.18810.66290.45980.104*0.50
H1'0.17770.66140.46570.104*0.50
N20.3606 (2)0.5812 (3)0.42290 (16)0.0689 (7)
H20.42940.55640.41970.083*
N30.2883 (4)0.2769 (4)0.0621 (3)0.0964 (10)
N40.6288 (3)0.5175 (4)0.1510 (2)0.0907 (9)
C10.1543 (7)0.7215 (9)0.5861 (6)0.074 (3)0.50
H1A0.19900.77350.63130.088*0.50
C20.0991 (8)0.5900 (9)0.6317 (6)0.084 (3)0.50
H2A0.15290.52030.65370.101*0.50
H2B0.05200.53980.58850.101*0.50
C30.0323 (6)0.6513 (8)0.7122 (4)0.094 (2)0.50
H3A−0.00550.57090.74200.113*0.50
H3B0.08070.69640.75670.113*0.50
C4−0.0488 (6)0.7647 (9)0.6791 (5)0.106 (3)0.50
H4A−0.10090.71710.63890.127*0.50
H4B−0.08790.80400.73090.127*0.50
C50.0049 (6)0.8899 (8)0.6289 (5)0.098 (3)0.50
H5A0.05320.94270.67000.117*0.50
H5B−0.04960.95860.60690.117*0.50
C60.0701 (8)0.8278 (11)0.5471 (5)0.091 (3)0.50
H6A0.02220.77640.50510.109*0.50
H6B0.10540.90750.51460.109*0.50
C1'0.1883 (7)0.7287 (12)0.6020 (6)0.121 (6)0.50
H1B0.25300.76920.63210.145*0.50
C2'0.1393 (7)0.6133 (12)0.6672 (7)0.101 (4)0.50
H2C0.18910.53120.67470.121*0.50
H2D0.12770.65760.72670.121*0.50
C3'0.0326 (8)0.5580 (10)0.6290 (9)0.149 (6)0.50
H3C0.00250.48460.66990.179*0.50
H3D0.04480.51120.57040.179*0.50
C4'−0.0484 (6)0.6857 (12)0.6172 (9)0.146 (5)0.50
H4C−0.06350.73000.67600.175*0.50
H4D−0.11590.64870.59170.175*0.50
C5'0.0006 (8)0.8018 (12)0.5529 (10)0.150 (5)0.50
H5C0.01070.75860.49300.180*0.50
H5D−0.04920.88420.54670.180*0.50
C6'0.1077 (7)0.8568 (10)0.5890 (8)0.106 (3)0.50
H6C0.09680.90630.64690.127*0.50
H6D0.13760.92810.54660.127*0.50
C70.3244 (3)0.6318 (3)0.5079 (2)0.0695 (8)
C80.3013 (3)0.5664 (4)0.3450 (2)0.0755 (9)
C90.3604 (3)0.5071 (4)0.2637 (2)0.0701 (8)
C100.3015 (3)0.4227 (4)0.2026 (2)0.0757 (9)
H100.22880.40250.21310.091*
C110.3514 (3)0.3689 (3)0.1262 (2)0.0753 (9)
C120.4585 (3)0.3965 (3)0.1073 (2)0.0751 (9)
H120.49160.35820.05560.090*
C130.5142 (3)0.4833 (3)0.1684 (2)0.0700 (8)
C140.4681 (3)0.5400 (3)0.2462 (2)0.0691 (8)
H140.50820.59880.28600.083*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0966 (7)0.1080 (8)0.0695 (5)0.0228 (6)0.0037 (5)−0.0177 (5)
O10.0737 (17)0.145 (3)0.1016 (18)0.0229 (17)−0.0108 (14)−0.0007 (17)
O20.127 (3)0.161 (3)0.135 (3)−0.052 (3)−0.019 (2)−0.027 (2)
O30.144 (3)0.126 (3)0.136 (3)−0.003 (2)−0.014 (2)−0.066 (2)
O40.117 (2)0.121 (2)0.134 (2)−0.0209 (19)0.045 (2)−0.043 (2)
O50.108 (2)0.131 (2)0.1037 (19)−0.0431 (19)0.0195 (17)−0.0334 (18)
N10.0751 (18)0.095 (2)0.0897 (19)0.0212 (16)0.0215 (15)0.0104 (16)
N20.0680 (15)0.0767 (16)0.0620 (14)0.0098 (13)0.0057 (12)0.0030 (12)
N30.111 (3)0.080 (2)0.098 (2)−0.012 (2)−0.019 (2)−0.0087 (18)
N40.102 (2)0.086 (2)0.0843 (19)−0.0157 (19)0.0192 (18)−0.0099 (17)
C10.058 (5)0.071 (6)0.093 (5)0.015 (4)0.026 (4)0.001 (4)
C20.097 (8)0.077 (5)0.078 (6)0.007 (6)0.011 (6)−0.005 (5)
C30.115 (6)0.100 (5)0.069 (4)−0.024 (5)0.029 (4)−0.017 (4)
C40.085 (5)0.131 (8)0.103 (6)−0.007 (5)0.020 (5)−0.071 (6)
C50.085 (5)0.095 (6)0.114 (6)0.018 (4)0.022 (5)−0.037 (5)
C60.070 (6)0.099 (7)0.103 (7)0.023 (6)−0.007 (5)−0.006 (5)
C1'0.088 (8)0.119 (11)0.157 (11)0.041 (7)0.051 (7)0.032 (8)
C2'0.087 (7)0.128 (8)0.087 (7)−0.004 (6)0.009 (5)0.007 (6)
C3'0.106 (8)0.160 (12)0.180 (12)−0.038 (8)−0.043 (8)0.069 (10)
C4'0.071 (5)0.162 (10)0.203 (13)−0.001 (7)−0.014 (7)0.077 (10)
C5'0.099 (8)0.124 (9)0.227 (15)−0.010 (8)−0.057 (9)0.049 (10)
C6'0.090 (7)0.092 (7)0.136 (9)0.007 (5)−0.004 (6)0.000 (6)
C70.076 (2)0.0639 (18)0.0689 (18)0.0095 (16)0.0127 (16)0.0061 (14)
C80.077 (2)0.076 (2)0.073 (2)0.0066 (18)−0.0027 (17)0.0090 (16)
C90.083 (2)0.0665 (18)0.0607 (16)0.0028 (17)−0.0076 (15)0.0113 (15)
C100.078 (2)0.0711 (19)0.077 (2)−0.0019 (17)−0.0112 (17)0.0110 (17)
C110.096 (3)0.0574 (18)0.0726 (19)−0.0027 (18)−0.0183 (18)0.0045 (15)
C120.102 (3)0.0593 (18)0.0641 (18)0.0011 (18)−0.0014 (18)0.0019 (15)
C130.083 (2)0.0607 (17)0.0665 (18)−0.0054 (16)−0.0008 (16)0.0053 (15)
C140.084 (2)0.0631 (18)0.0598 (16)−0.0052 (16)−0.0035 (16)0.0051 (14)
Geometric parameters (Å, °) top
S1—C71.659 (4)C5—H5B0.9700
O1—C81.215 (4)C6—H6A0.9700
O2—N31.210 (5)C6—H6B0.9700
O3—N31.200 (4)C1'—C6'1.539 (8)
O4—N41.221 (4)C1'—C2'1.542 (8)
O5—N41.213 (4)C1'—H1B0.9800
N1—C71.305 (4)C2'—C3'1.512 (8)
N1—C11.452 (6)C2'—H2C0.9700
N1—C1'1.481 (8)C2'—H2D0.9700
N1—H10.8800C3'—C4'1.537 (9)
N1—H1'0.8800C3'—H3C0.9700
N2—C81.358 (4)C3'—H3D0.9700
N2—C71.402 (4)C4'—C5'1.537 (8)
N2—H20.8800C4'—H4C0.9700
N3—C111.474 (5)C4'—H4D0.9700
N4—C131.471 (5)C5'—C6'1.505 (8)
C1—C61.524 (8)C5'—H5C0.9700
C1—C21.527 (8)C5'—H5D0.9700
C1—H1A0.9800C6'—H6C0.9700
C2—C31.547 (7)C6'—H6D0.9700
C2—H2A0.9700C8—C91.501 (5)
C2—H2B0.9700C9—C101.380 (5)
C3—C41.511 (8)C9—C141.388 (4)
C3—H3A0.9700C10—C111.370 (5)
C3—H3B0.9700C10—H100.9300
C4—C51.507 (7)C11—C121.375 (5)
C4—H4A0.9700C12—C131.372 (5)
C4—H4B0.9700C12—H120.9300
C5—C61.552 (8)C13—C141.376 (4)
C5—H5A0.9700C14—H140.9300
C7—N1—C1133.3 (5)C2'—C1'—H1B107.3
C7—N1—C1'114.9 (5)C3'—C2'—C1'109.8 (7)
C7—N1—H1113.3C3'—C2'—H2C109.7
C1—N1—H1113.3C1'—C2'—H2C109.7
C7—N1—H1'122.6C3'—C2'—H2D109.7
C1'—N1—H1'122.6C1'—C2'—H2D109.7
C8—N2—C7127.2 (3)H2C—C2'—H2D108.2
C8—N2—H2116.4C2'—C3'—C4'110.9 (7)
C7—N2—H2116.4C2'—C3'—H3C109.5
O3—N3—O2123.5 (4)C4'—C3'—H3C109.5
O3—N3—C11119.1 (4)C2'—C3'—H3D109.5
O2—N3—C11117.4 (4)C4'—C3'—H3D109.5
O5—N4—O4124.5 (3)H3C—C3'—H3D108.1
O5—N4—C13117.9 (3)C3'—C4'—C5'109.0 (7)
O4—N4—C13117.6 (3)C3'—C4'—H4C109.9
N1—C1—C6108.7 (6)C5'—C4'—H4C109.9
N1—C1—C2109.8 (6)C3'—C4'—H4D109.9
C6—C1—C2110.6 (7)C5'—C4'—H4D109.9
N1—C1—H1A109.3H4C—C4'—H4D108.3
C6—C1—H1A109.3C6'—C5'—C4'111.1 (7)
C2—C1—H1A109.3C6'—C5'—H5C109.4
C1—C2—C3107.2 (5)C4'—C5'—H5C109.4
C1—C2—H2A110.3C6'—C5'—H5D109.4
C3—C2—H2A110.3C4'—C5'—H5D109.4
C1—C2—H2B110.3H5C—C5'—H5D108.0
C3—C2—H2B110.3C5'—C6'—C1'111.1 (7)
H2A—C2—H2B108.5C5'—C6'—H6C109.4
C4—C3—C2110.7 (5)C1'—C6'—H6C109.4
C4—C3—H3A109.5C5'—C6'—H6D109.4
C2—C3—H3A109.5C1'—C6'—H6D109.4
C4—C3—H3B109.5H6C—C6'—H6D108.0
C2—C3—H3B109.5N1—C7—N2116.4 (3)
H3A—C3—H3B108.1N1—C7—S1125.6 (3)
C5—C4—C3112.0 (6)N2—C7—S1118.0 (2)
C5—C4—H4A109.2O1—C8—N2124.1 (3)
C3—C4—H4A109.2O1—C8—C9119.7 (3)
C5—C4—H4B109.2N2—C8—C9116.2 (3)
C3—C4—H4B109.2C10—C9—C14120.0 (3)
H4A—C4—H4B107.9C10—C9—C8117.2 (3)
C4—C5—C6109.7 (6)C14—C9—C8122.8 (3)
C4—C5—H5A109.7C11—C10—C9119.2 (3)
C6—C5—H5A109.7C11—C10—H10120.4
C4—C5—H5B109.7C9—C10—H10120.4
C6—C5—H5B109.7C10—C11—C12122.6 (3)
H5A—C5—H5B108.2C10—C11—N3118.8 (4)
C1—C6—C5107.1 (5)C12—C11—N3118.6 (3)
C1—C6—H6A110.3C13—C12—C11116.7 (3)
C5—C6—H6A110.3C13—C12—H12121.6
C1—C6—H6B110.3C11—C12—H12121.6
C5—C6—H6B110.3C12—C13—C14123.1 (3)
H6A—C6—H6B108.5C12—C13—N4119.0 (3)
N1—C1'—C6'110.4 (8)C14—C13—N4117.9 (3)
N1—C1'—C2'115.0 (8)C13—C14—C9118.3 (3)
C6'—C1'—C2'109.4 (6)C13—C14—H14120.8
N1—C1'—H1B107.3C9—C14—H14120.8
C6'—C1'—H1B107.3
C7—N1—C1—C6147.6 (6)C8—N2—C7—N1−0.6 (5)
C1'—N1—C1—C6134 (2)C8—N2—C7—S1−179.3 (3)
C7—N1—C1—C2−91.4 (9)C7—N2—C8—O10.6 (6)
C1'—N1—C1—C2−105 (2)C7—N2—C8—C9−179.1 (3)
N1—C1—C2—C3177.3 (7)O1—C8—C9—C10−31.7 (5)
C6—C1—C2—C3−62.8 (10)N2—C8—C9—C10148.0 (3)
C1—C2—C3—C457.7 (10)O1—C8—C9—C14145.0 (4)
C2—C3—C4—C5−56.9 (9)N2—C8—C9—C14−35.3 (4)
C3—C4—C5—C657.5 (9)C14—C9—C10—C111.7 (5)
N1—C1—C6—C5−175.5 (8)C8—C9—C10—C11178.6 (3)
C2—C1—C6—C563.9 (10)C9—C10—C11—C12−0.5 (5)
C4—C5—C6—C1−59.6 (10)C9—C10—C11—N3179.1 (3)
C7—N1—C1'—C6'141.7 (5)O3—N3—C11—C10179.4 (4)
C1—N1—C1'—C6'−49.4 (18)O2—N3—C11—C101.2 (5)
C7—N1—C1'—C2'−94.0 (7)O3—N3—C11—C12−1.1 (5)
C1—N1—C1'—C2'74.9 (19)O2—N3—C11—C12−179.3 (4)
N1—C1'—C2'—C3'−66.7 (10)C10—C11—C12—C13−0.8 (5)
C6'—C1'—C2'—C3'58.1 (11)N3—C11—C12—C13179.6 (3)
C1'—C2'—C3'—C4'−59.8 (12)C11—C12—C13—C140.9 (5)
C2'—C3'—C4'—C5'58.6 (13)C11—C12—C13—N4−179.4 (3)
C3'—C4'—C5'—C6'−57.3 (14)O5—N4—C13—C12172.3 (3)
C4'—C5'—C6'—C1'57.8 (13)O4—N4—C13—C12−7.0 (5)
N1—C1'—C6'—C5'69.9 (10)O5—N4—C13—C14−8.0 (5)
C2'—C1'—C6'—C5'−57.5 (11)O4—N4—C13—C14172.6 (3)
C1—N1—C7—N2177.5 (5)C12—C13—C14—C90.3 (5)
C1'—N1—C7—N2−177.5 (5)N4—C13—C14—C9−179.4 (3)
C1—N1—C7—S1−3.8 (7)C10—C9—C14—C13−1.6 (5)
C1'—N1—C7—S11.1 (6)C8—C9—C14—C13−178.3 (3)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O10.881.892.639 (4)142
N1—H1'···O10.881.992.639 (4)130
N2—H2···S1i0.882.653.449 (3)152
Symmetry codes: (i) −x+1, −y+1, −z+1.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O10.881.892.639 (4)142
N1—H1'···O10.881.992.639 (4)130
N2—H2···S1i0.882.653.449 (3)152
Symmetry codes: (i) −x+1, −y+1, −z+1.
Acknowledgements top

The authors are grateful to Allama Iqbal Open University, Islamabad, Pakistan, for the allocation of research and analytical laboratory facilities. The authors also thank the University of Malaya for supporting this study.

references
References top

Agilent (2010). CrysAlis PRO. Agilent Technologies, Yarnton, England.

Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.

Dzulkifli, N. N., Farina, Y., Yamin, B. M., Baba, I. & Tiekink, E. R. T. (2011). Acta Cryst. E67, o872.

Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.

Gunasekaran, N., Karvembu, R., Ng, S. W. & Tiekink, E. R. T. (2010). Acta Cryst. E66, o2601.

Saeed, S., Rashid, N., Jones, P. G. & Tahir, A. (2011). J. Heterocycl. Chem. 48, 74–84.

Saeed, S., Rashid, N. & Wong, W.-T. (2010). Acta Cryst. E66, o980.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Venkatachalam, T. K., Mao, C. & Uckun, F. M. (2004). Bioorg. Med. Chem. 12, 4275–4284.

Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.