1,1,2,2-Tetra­kis(1,3-benzoxazol-2-yl)ethene

Hagos, T.K.; Nogai, S.D.; Dobrzańska, L.; Cronje, S.; Raubenheimer, H.G.

doi:10.1107/S1600536811026924

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 67| Part 8| August 2011| Page o2014

doi:10.1107/S1600536811026924

Open

access

1,1,2,2-Tetrakis(1,3-benzoxazol-2-yl)ethene

Tesfamariam K. Hagos,^a Stefan D. Nogai,^a Liliana Dobrzańska,^a,^b ^* Stephanie Cronje ^a,^c and Helgard G. Raubenheimer ^a

^aDepartment of Chemistry, University of Stellenbosch, Private Bag X1, Matieland, South Africa, ^bDepartment of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F - bus 2404, B-3001 Heverlee, Belgium, and ^cInstitut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, D-60348 Frankfurt am Main, Germany
^*Correspondence e-mail: lianger@sun.ac.za

(Received 1 July 2011; accepted 5 July 2011; online 13 July 2011)

The title compound, C₃₀H₁₆N₄O₄, reveals $[\overline1]$ crystallographic and molecular symmetry and accordingly the asymmetric unit comprises one half-molecule. The dihedral angle between the planes of the two geminal benzoxazole rings is 74.39 (5)°. The packing features weak C—H⋯N and π–π interactions [centroid–centroid distance = 3.652 (1) Å].

Related literature

For the chloroform disolvate of 1,1,2,2-tetrakis(1,3-benzothiazol-2-yl)ethene, see: Hagos et al. (2010 ). For bond lengths in the benzoxazole moiety in related compounds, see: Jian et al. (2007 ); Lokaj et al. (1997 ); Muir et al. (1992 ). For details of the cut-off applied for C—H⋯N interactions, see: Desiraju & Steiner (2006 ). For the synthesis of AuCl(PPh₃), see: Bruce et al. (1989 ).

Experimental

Crystal data

C₃₀H₁₆N₄O₄
M_r = 496.47
Monoclinic, P 2₁ /c
a = 9.2697 (9) Å
b = 16.1943 (16) Å
c = 8.0332 (8) Å
β = 104.395 (2)°
V = 1168.1 (2) Å³
Z = 2
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 273 K
0.30 × 0.25 × 0.15 mm

Data collection

Bruker APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1997 ) T_min = 0.972, T_max = 0.986
6999 measured reflections
2717 independent reflections
2458 reflections with I > 2σ(I)
R_int = 0.021

Refinement

R[F² > 2σ(F²)] = 0.049
wR(F²) = 0.121
S = 1.06
2717 reflections
172 parameters
H-atom parameters constrained
Δρ_max = 0.37 e Å⁻³
Δρ_min = −0.30 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C7—H7⋯N12ⁱ	0.93	2.71	3.348 (2)	127
C17—H17⋯N3ⁱⁱ	0.93	2.71	3.580 (2)	153
C14—H14⋯N12ⁱⁱⁱ	0.93	2.75	3.387 (2)	127
Symmetry codes: (i) -x, -y+1, -z+2; (ii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iii) -x+1, -y+1, -z+1.

Data collection: SMART (Bruker, 2001 ); cell refinement: SAINT (Bruker, 2002 ); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811026924/kp2340sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811026924/kp2340Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811026924/kp2340Isup3.cml

checkCIF report

Comment top

The title compound is reminiscent of the crystal structure of 1,1,2,2-tetrakis(1,3-benzothiazol-2-yl)ethene chloroform solvate (Hagos et al., 2010) and was isolated in a similar way. The asymmetric unit consists of half of the molecule with the other part being generated by an inversion centre (Fig. 1). The conformation of the molecule resembles that of the previous compound with a dihedral angle between the planes of the benzoxazole rings attached to the same carbon of 74.39 (5)°, whereas the corresponding value in the benzothiazole derivative was 85.74 (4)°. The bond length of 1.356 (3) Å for C1—C1ⁱ (symmetry operation (i): -x,1 - y,1 - z) is almost identical to that in the earlier described structure (1.359 (3) Å). The bond lengths for the benzoxazole rings are comparable with previously reported values (Jian et al., 2007; Lokaj et al., 1997; Muir et al., 1992). The packing is dominated by weak C—H···N (Table 1) and π–π interactions. The hydrogen bonds between C7—H7···N12 and C17—H17···N3 generate corrugated layers which are stabilised by π-π stacking interactions of the oxazole and phenyl rings with a distance of 3.652 (1) Å between the centroids of these rings (symmetry operation: -x,1 - y,2 - z) and ca. 1.41 Å slippage. In addition to this, N12 acts as a bifurcated hydrogen bond acceptor and interlinks the layers through C14—H14···N12 weak interaction to form a three-dimensional assembly (Fig. 2).

Related literature top

For the chloroform disolvate of 1,1,2,2-tetrakis(1,3-benzothiazol-2-yl)ethene, see: Hagos et al. (2010). For bond lengths in the benzoxazole moiety in related compounds, see: Jian et al. (2007); Lokaj et al. (1997); Muir et al. (1992). For details of the cut-off applied for C—H···N interactions, see: Desiraju & Steiner (2006). For the synthesis of AuCl(PPh₃), see: Bruce et al. (1989).

Experimental top

A solution of bis(2-benzoxazolyl)methane (0.075 g, 0.30 mmol) in THF (20 mL) at 253 K was treated with n-BuLi in n-hexane (0.25 mL, 1.4 M, 0.35 mmol) and stirred for 1 h. The temperature was then slowly raised to room temperature. A suspension of an excess of S₈ (ca 2 mol equivalents) in 20 mL of THF was added to the mixture at 253 K and stirred for 1 h. After treating the resulting mixture with a solution of AuCl(PPh₃) (0.15 g, 0.33 mmol) (Bruce et al., 1989) in THF (20 mL), the mixture was allowed to slowly warm to ambient temperature while stirring. The solvent was removed under reduced pressure. Crystallisation of a dichloromethane solution of the residue layered with n-heptane at 253 K afforded light yellow crystals. Single crystal X-ray studies revealed that the unexpected oxidative dimerisation of bis(2-benzoxazolyl)methane had occurred to yield the title compound.

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Unlabeled atoms are related to the labeled ones by the symmetry operation (i) -x,1 - y,1 - z.
	Fig. 2. Representation of the packing viewed down the c axis. The corrugated layers formed by weak C—H···N and π–π interactions are indicated in blue and red; C14—H14···N12 contacts between these layers are shown as dotted light-blue lines.

1,1,2,2-Tetrakis(1,3-benzoxazol-2-yl)ethene top

Crystal data top

C₃₀H₁₆N₄O₄	F(000) = 512
M_r = 496.47	D_x = 1.412 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3523 reflections
a = 9.2697 (9) Å	θ = 2.5–28.3°
b = 16.1943 (16) Å	µ = 0.10 mm⁻¹
c = 8.0332 (8) Å	T = 273 K
β = 104.395 (2)°	Block, yellow
V = 1168.1 (2) Å³	0.30 × 0.25 × 0.15 mm
Z = 2

Data collection top

Bruker APEX CCD area-detector diffractometer	2717 independent reflections
Radiation source: fine-focus sealed tube	2458 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.021
ω scans	θ_max = 28.3°, θ_min = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −12→12
T_min = 0.972, T_max = 0.986	k = −17→21
6999 measured reflections	l = −10→7

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.121	H-atom parameters constrained
S = 1.06	w = 1/[σ²(F_o²) + (0.0513P)² + 0.8168P] where P = (F_o² + 2F_c²)/3
2717 reflections	(Δ/σ)_max < 0.001
172 parameters	Δρ_max = 0.37 e Å⁻³
0 restraints	Δρ_min = −0.30 e Å⁻³

Crystal data top

C₃₀H₁₆N₄O₄	V = 1168.1 (2) Å³
M_r = 496.47	Z = 2
Monoclinic, P2₁/c	Mo Kα radiation
a = 9.2697 (9) Å	µ = 0.10 mm⁻¹
b = 16.1943 (16) Å	T = 273 K
c = 8.0332 (8) Å	0.30 × 0.25 × 0.15 mm
β = 104.395 (2)°

Data collection top

Bruker APEX CCD area-detector diffractometer	2717 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	2458 reflections with I > 2σ(I)
T_min = 0.972, T_max = 0.986	R_int = 0.021
6999 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.049	0 restraints
wR(F²) = 0.121	H-atom parameters constrained
S = 1.06	Δρ_max = 0.37 e Å⁻³
2717 reflections	Δρ_min = −0.30 e Å⁻³
172 parameters

Special details top

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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.02783 (16)	0.46822 (9)	0.55330 (19)	0.0186 (3)
C2	−0.02821 (16)	0.44239 (9)	0.69934 (19)	0.0199 (3)
N3	0.01487 (14)	0.37588 (8)	0.78861 (16)	0.0197 (3)
C4	−0.06473 (16)	0.37680 (9)	0.91493 (19)	0.0196 (3)
C5	−0.06558 (18)	0.32189 (10)	1.0482 (2)	0.0240 (3)
H5	−0.0059	0.2749	1.0664	0.029*
C6	−0.15995 (18)	0.34088 (10)	1.1524 (2)	0.0258 (3)
H6	−0.1640	0.3055	1.2423	0.031*
C7	−0.24923 (18)	0.41171 (10)	1.1263 (2)	0.0262 (4)
H7	−0.3114	0.4218	1.1988	0.031*
C8	−0.24768 (18)	0.46738 (10)	0.9955 (2)	0.0246 (3)
H8	−0.3060	0.5148	0.9782	0.029*
C9	−0.15338 (16)	0.44734 (9)	0.89261 (19)	0.0199 (3)
O10	−0.12962 (12)	0.48989 (7)	0.75253 (14)	0.0217 (3)
C11	0.15956 (17)	0.42084 (10)	0.53413 (19)	0.0217 (3)
N12	0.29464 (13)	0.44984 (7)	0.58136 (16)	0.0179 (3)
C13	0.38086 (17)	0.38841 (9)	0.53122 (19)	0.0194 (3)
C14	0.53275 (17)	0.38556 (10)	0.5437 (2)	0.0251 (3)
H14	0.5959	0.4286	0.5920	0.030*
C15	0.58507 (18)	0.31551 (11)	0.4807 (2)	0.0284 (4)
H15	0.6863	0.3111	0.4872	0.034*
C16	0.4904 (2)	0.25091 (11)	0.4074 (2)	0.0309 (4)
H16	0.5307	0.2048	0.3666	0.037*
C17	0.33806 (19)	0.25342 (10)	0.3935 (2)	0.0284 (4)
H17	0.2746	0.2106	0.3450	0.034*
C18	0.28725 (16)	0.32445 (9)	0.45730 (19)	0.0205 (3)
O19	0.14322 (12)	0.34621 (7)	0.46062 (15)	0.0258 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0167 (7)	0.0186 (7)	0.0206 (7)	−0.0016 (5)	0.0050 (5)	−0.0009 (5)
C2	0.0164 (7)	0.0216 (7)	0.0211 (7)	−0.0023 (5)	0.0037 (6)	−0.0013 (6)
N3	0.0192 (6)	0.0191 (6)	0.0211 (6)	−0.0002 (5)	0.0057 (5)	0.0020 (5)
C4	0.0190 (7)	0.0195 (7)	0.0197 (7)	−0.0035 (5)	0.0037 (6)	−0.0023 (5)
C5	0.0274 (8)	0.0202 (7)	0.0233 (8)	−0.0018 (6)	0.0044 (6)	0.0016 (6)
C6	0.0314 (8)	0.0260 (8)	0.0199 (7)	−0.0096 (6)	0.0062 (6)	−0.0002 (6)
C7	0.0272 (8)	0.0306 (8)	0.0236 (8)	−0.0072 (6)	0.0114 (6)	−0.0070 (6)
C8	0.0236 (8)	0.0249 (8)	0.0266 (8)	−0.0004 (6)	0.0088 (6)	−0.0039 (6)
C9	0.0202 (7)	0.0197 (7)	0.0189 (7)	−0.0033 (5)	0.0035 (5)	−0.0007 (6)
O10	0.0217 (5)	0.0216 (5)	0.0234 (5)	0.0014 (4)	0.0084 (4)	0.0019 (4)
C11	0.0239 (8)	0.0227 (7)	0.0197 (7)	0.0061 (6)	0.0080 (6)	0.0067 (6)
N12	0.0155 (6)	0.0149 (6)	0.0246 (6)	0.0013 (4)	0.0075 (5)	0.0011 (5)
C13	0.0210 (7)	0.0180 (7)	0.0202 (7)	0.0026 (5)	0.0069 (6)	0.0017 (5)
C14	0.0202 (7)	0.0283 (8)	0.0270 (8)	−0.0029 (6)	0.0062 (6)	0.0031 (6)
C15	0.0203 (8)	0.0376 (9)	0.0291 (8)	0.0079 (7)	0.0097 (6)	0.0068 (7)
C16	0.0343 (9)	0.0297 (9)	0.0308 (9)	0.0113 (7)	0.0123 (7)	−0.0028 (7)
C17	0.0311 (9)	0.0246 (8)	0.0291 (8)	−0.0005 (6)	0.0068 (7)	−0.0056 (6)
C18	0.0192 (7)	0.0223 (7)	0.0200 (7)	0.0019 (6)	0.0047 (6)	0.0012 (6)
O19	0.0220 (6)	0.0265 (6)	0.0283 (6)	0.0015 (4)	0.0051 (5)	−0.0013 (5)

Geometric parameters (Å, º) top

C1—C1ⁱ	1.356 (3)	C9—O10	1.3830 (18)
C1—C2	1.458 (2)	C11—N12	1.302 (2)
C1—C11	1.482 (2)	C11—O19	1.3370 (19)
C2—N3	1.3006 (19)	N12—C13	1.3966 (18)
C2—O10	1.3628 (18)	C13—C18	1.386 (2)
N3—C4	1.3952 (19)	C13—C14	1.387 (2)
C4—C9	1.393 (2)	C14—C15	1.379 (2)
C4—C5	1.394 (2)	C14—H14	0.9300
C5—C6	1.387 (2)	C15—C16	1.398 (3)
C5—H5	0.9300	C15—H15	0.9300
C6—C7	1.399 (2)	C16—C17	1.389 (2)
C6—H6	0.9300	C16—H16	0.9300
C7—C8	1.387 (2)	C17—C18	1.388 (2)
C7—H7	0.9300	C17—H17	0.9300
C8—C9	1.382 (2)	C18—O19	1.3874 (18)
C8—H8	0.9300

C1ⁱ—C1—C2	124.77 (17)	C2—O10—C9	103.63 (11)
C1ⁱ—C1—C11	121.42 (17)	N12—C11—O19	116.73 (13)
C2—C1—C11	113.75 (12)	N12—C11—C1	122.70 (14)
N3—C2—O10	115.83 (13)	O19—C11—C1	120.53 (13)
N3—C2—C1	124.01 (14)	C11—N12—C13	103.70 (12)
O10—C2—C1	120.14 (13)	C18—C13—C14	121.47 (14)
C2—N3—C4	104.29 (12)	C18—C13—N12	108.27 (13)
C9—C4—C5	120.43 (14)	C14—C13—N12	130.25 (14)
C9—C4—N3	108.48 (13)	C15—C14—C13	116.37 (15)
C5—C4—N3	131.09 (14)	C15—C14—H14	121.8
C6—C5—C4	116.56 (15)	C13—C14—H14	121.8
C6—C5—H5	121.7	C14—C15—C16	121.96 (15)
C4—C5—H5	121.7	C14—C15—H15	119.0
C5—C6—C7	121.96 (15)	C16—C15—H15	119.0
C5—C6—H6	119.0	C17—C16—C15	122.06 (15)
C7—C6—H6	119.0	C17—C16—H16	119.0
C8—C7—C6	121.95 (15)	C15—C16—H16	119.0
C8—C7—H7	119.0	C18—C17—C16	115.22 (15)
C6—C7—H7	119.0	C18—C17—H17	122.4
C9—C8—C7	115.30 (15)	C16—C17—H17	122.4
C9—C8—H8	122.4	C13—C18—O19	107.75 (13)
C7—C8—H8	122.4	C13—C18—C17	122.92 (14)
C8—C9—O10	128.44 (14)	O19—C18—C17	129.34 (14)
C8—C9—C4	123.79 (14)	C11—O19—C18	103.54 (12)
O10—C9—C4	107.77 (13)

C1ⁱ—C1—C2—N3	171.93 (18)	C1ⁱ—C1—C11—N12	75.2 (2)
C11—C1—C2—N3	−11.0 (2)	C2—C1—C11—N12	−102.04 (16)
C1ⁱ—C1—C2—O10	−9.6 (3)	C1ⁱ—C1—C11—O19	−102.5 (2)
C11—C1—C2—O10	167.47 (13)	C2—C1—C11—O19	80.33 (17)
O10—C2—N3—C4	0.47 (17)	O19—C11—N12—C13	1.25 (17)
C1—C2—N3—C4	178.99 (13)	C1—C11—N12—C13	−176.47 (13)
C2—N3—C4—C9	−0.45 (15)	C11—N12—C13—C18	−0.89 (16)
C2—N3—C4—C5	−179.84 (16)	C11—N12—C13—C14	178.08 (16)
C9—C4—C5—C6	1.1 (2)	C18—C13—C14—C15	−0.7 (2)
N3—C4—C5—C6	−179.58 (15)	N12—C13—C14—C15	−179.59 (15)
C4—C5—C6—C7	−0.4 (2)	C13—C14—C15—C16	0.3 (2)
C5—C6—C7—C8	−0.5 (2)	C14—C15—C16—C17	0.0 (3)
C6—C7—C8—C9	0.7 (2)	C15—C16—C17—C18	0.1 (3)
C7—C8—C9—O10	179.17 (14)	C14—C13—C18—O19	−178.77 (13)
C7—C8—C9—C4	0.0 (2)	N12—C13—C18—O19	0.32 (16)
C5—C4—C9—C8	−1.0 (2)	C14—C13—C18—C17	0.9 (2)
N3—C4—C9—C8	179.59 (14)	N12—C13—C18—C17	180.00 (14)
C5—C4—C9—O10	179.77 (13)	C16—C17—C18—C13	−0.6 (2)
N3—C4—C9—O10	0.30 (16)	C16—C17—C18—O19	179.05 (15)
N3—C2—O10—C9	−0.29 (16)	N12—C11—O19—C18	−1.06 (17)
C1—C2—O10—C9	−178.87 (13)	C1—C11—O19—C18	176.71 (13)
C8—C9—O10—C2	−179.27 (15)	C13—C18—O19—C11	0.38 (15)
C4—C9—O10—C2	−0.03 (15)	C17—C18—O19—C11	−179.28 (16)

Symmetry code: (i) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7···N12ⁱⁱ	0.93	2.71	3.348 (2)	127
C17—H17···N3ⁱⁱⁱ	0.93	2.71	3.580 (2)	153
C14—H14···N12^iv	0.93	2.75	3.387 (2)	127

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

Experimental details

Crystal data
Chemical formula	C₃₀H₁₆N₄O₄
M_r	496.47
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	273
a, b, c (Å)	9.2697 (9), 16.1943 (16), 8.0332 (8)
β (°)	104.395 (2)
V (Å³)	1168.1 (2)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.10
Crystal size (mm)	0.30 × 0.25 × 0.15

Data collection
Diffractometer	Bruker APEX CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 1997)
T_min, T_max	0.972, 0.986
No. of measured, independent and observed [I > 2σ(I)] reflections	6999, 2717, 2458
R_int	0.021
(sin θ/λ)_max (Å⁻¹)	0.666

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.049, 0.121, 1.06
No. of reflections	2717
No. of parameters	172
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.37, −0.30

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), Mercury (Macrae et al., 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7···N12ⁱ	0.93	2.71	3.348 (2)	127
C17—H17···N3ⁱⁱ	0.93	2.71	3.580 (2)	153
C14—H14···N12ⁱⁱⁱ	0.93	2.75	3.387 (2)	127

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

Acknowledgements

The authors thank the National Research Foundation of South Africa for financial support. LD also thanks the Research Foundation Flanders (FWO).

References

Bruce, M. I., Nicholson, B. K. & Shawkataly, O. B. (1989). Inorg. Synth. 26, 324–326. CrossRef CAS Web of Science Google Scholar
Bruker (2001). SMART. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker (2002). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Desiraju, G. R. & Steiner, T. (2006). In The Weak Hydrogen Bond in Structural Chemistry and Biology. Oxford University Press. Google Scholar
Hagos, T. K., Nogai, S. D., Dobrzańska, L., Cronje, S. & Raubenheimer, H. G. (2010). Acta Cryst. E66, o2378. Web of Science CSD CrossRef IUCr Journals Google Scholar
Jian, F.-F., Yi, W., Wang, L.-M. & Wang, J. (2007). Acta Cryst. E63, o3887. Web of Science CSD CrossRef IUCr Journals Google Scholar
Lokaj, J., Kettmann, V., Stetinová, J., Kada, R. & Vrábel, V. (1997). Acta Cryst. C53, 1358–1359. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470. Web of Science CrossRef CAS IUCr Journals Google Scholar
Muir, M. M., Cox, O., Bernard, L. & Muir, J. A. (1992). Acta Cryst. C48, 583–585. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Sheldrick, G. M. (1997). SADABS. University of Göttingen, Germany. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar