2-Meth­oxy­anilinium trichlorido­stannate(II)

Karoui, S.; Kamoun, S.; Michaud, F.

doi:10.1107/S1600536813005096

metal-organic compounds

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ISSN: 2056-9890

Volume 69| Part 4| April 2013| Pages m187-m188

doi:10.1107/S1600536813005096

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2-Methoxyanilinium trichloridostannate(II)

Sahel Karoui,^a Slaheddine Kamoun ^a ^* and François Michaud ^b

^aLaboratoire de Génie des Matériaux et Environnement, École Nationale d'Ingénieurs de Sfax, BP 1173, Sfax, Tunisia, and ^bService commun d'analyse par diffraction des rayons X, Université de Brest, 6 Avenue Victor Le Gorgeu, CS 93837, F-29238 Brest Cedex 3, France
^*Correspondence e-mail: slah.kamoun@gmail.com

(Received 1 February 2013; accepted 21 February 2013; online 6 March 2013)

The title compound, (C₇H₁₀NO)[SnCl₃], is a new compound with non-linear optical (NLO) properties. The structure is pseudocentrosymmetric; the absence of an inversion centre was proved by the Kurtz and Perry method showing a significant second harmonic generation (SHG) signal about ten times lower than that from potassium dihydrogenphosphate. The crystal structure exhibits alternating organic and inorganic layers parallel to the ab plane, which are stabilized by intermolecular N—H⋯Cl interactions.

Related literature

For related structures, see: Zhang et al. (2009 ). For the effects of substituents on the internal angles of the benzene ring, see: Domenicano & Murray-Rust (1979 ). For NLO and SHG, see: Kurtz & Perry (1968 ); Kamoun et al. (1995 ). For ferroelectricity of related compounds, see: Ben Gozlen et al. (1994 ). For electric and dielectric properties of related compounds, see: Karoui et al. (2013 ).

Experimental

Crystal data

(C₇H₁₀NO)[SnCl₃]
M_r = 349.20
Orthorhombic, P 2₁ 2₁ 2₁
a = 7.2030 (2) Å
b = 8.3341 (3) Å
c = 19.5436 (6) Å
V = 1173.21 (6) Å³
Z = 4
Mo Kα radiation
μ = 2.82 mm⁻¹
T = 296 K
0.41 × 0.34 × 0.10 mm

Data collection

Agilent Xcalibur (Sapphire2) diffractometer
Absorption correction: multi-scan (CrysAlis RED; Agilent, 2012 ) T_min = 0.391, T_max = 0.765
8969 measured reflections
2392 independent reflections
2236 reflections with I > 2σ(I)
R_int = 0.019

Refinement

R[F² > 2σ(F²)] = 0.026
wR(F²) = 0.064
S = 1.14
2392 reflections
120 parameters
H-atom parameters constrained
Δρ_max = 0.89 e Å⁻³
Δρ_min = −0.69 e Å⁻³
Absolute structure: Flack (1983 ), 986 Friedel pairs
Flack parameter: 0.03 (5)

Table 1
Selected bond lengths (Å)

Sn1—Cl1	2.5437 (15)
Sn1—Cl2	2.6489 (11)
Sn1—Cl3	2.5139 (15)

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1C⋯Cl1ⁱ	0.89	2.51	3.339 (4)	155
N1—H1C⋯Cl3ⁱⁱ	0.89	2.85	3.418 (4)	123
N1—H1A⋯Cl3ⁱⁱⁱ	0.89	2.53	3.329 (4)	151
N1—H1B⋯Cl2	0.89	2.54	3.371 (6)	157
N1—H1B⋯Cl1	0.89	2.94	3.515 (4)	124
Symmetry codes: (i) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) $[-x+2, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iii) x-1, y, z.

Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO; data reduction: CrysAlis RED (Agilent, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg et al., 1999 ) and Mercury (Macrae et al., 2006 ); software used to prepare material for publication: WinGX (Farrugia, 2012 ) and publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536813005096/vn2066sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536813005096/vn2066Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536813005096/vn2066Isup3.cdx

checkCIF report

Comment top

Considerable attention has been devoted to inorganic-organic hybrid materials over recent years (Zhang et al., 2009). These hybrid materials have interesting physical properties such as ferroelectricity (Ben Gozlen et al., 1994), non-linear optics (Kamoun et al., 1995) as well as electrical conductivity and dielectric relaxation (Karoui et al., 2013). Herein we report the structure of a new non-linear optical material. The structure can be solved and refined in both P2₁2₁2₁ and Pmnb, the refinement in the latter space group being of less quality than the one in P2₁2₁2_1.The NLO response of C₇H₁₀NO.SnCl₃ has been evaluated by performing SHG on a powder sample using the Kurtz and Perry powder technique (Kurtz & Perry, 1968). The NLO effenciency of C₇H₁₀NO.SnCl₃ was found to be 10 times lower than KDP. [I²^ω/(I ^ω)²] _{C7H10NO.SnCl3}= 0.1[I²^ω/(I ^ω)²]_KDP, ruling out the possibility of the centrosymmetric space group.

The stereochemical activity of the non-bonding valence electrons on tin (II) in the title compound is evident in the asymmetric coordination environment adopted by this atom (Fig. 1). The primary coordination contacts from tin to the three chlorine atoms constitute the trichloro stannate anion [SnCl₃]^-. This anion is pyramidal with Sn—Cl distances of 2.5139 (15) Å, 2.5437 (15) Å, 2.6489 (11) Å (Table 1) and Cl—Sn—Cl bond angles of 93.82 (4), 85.52 (5) and 85.10 (5)°. One longer second contact (3.0075 (11) Å) to chlorine atoms on neighboring [SnCl₃]^- anions complete the fourfold coordinate geometry for tin and give rises to an infinite [SnCl₃]_n^n- chain along the b axis (Fig. 2). Each chain is characterized by a short Sn—Sn bond length of 4.2078 (2) Å and a Sn—Cl—Sn bridge angle of 95.92 (3)°. The benzene ring is practically planar with the greatest deviation from the six-atoms least squares plane being 0.0009 Å. The dihedral angle between two benzene rings of the formula unit is 14°. No stabilization is provided by π-π stacking interactions between the benzene rings of the cations (centroid-centroid distances = 4.362 (4) Å). The torsion angle O1—C1—C2—N1 is 0.2 (8)° indicating that the N1—C2 and C1—O1 groups are in the same plane as the benzene rings. The methoxy group of the organic cation makes an angle of 4(1)° with the plane of the phenyl ring and is in short intramolecular contact with O1 (d_N..O =2.621 (5) Å). The bond angles in the phenyl groups deviate significantly from the idealized value of 120° due to the effect of the substituent. In fact, it was established that the angular deformations of phenyl groups can be described as a sum of the effects of the different substituents (Domenicano & Murray-Rust, 1979). The benzene ring is regular with C—C—C angles in agreement with the expected sp² hybridation. The major contribution to the cohesion and the stability of this ionic structure comes from intermolecular N—H···Cl hydrogen bond interactions which include five relatively long contacts, with H···Cl and N..Cl distances ranging from 2.510 to 2.938 Å and 3.329 (4) Å to 3.515 (4) Å, respectively (Table 2, Fig.2).

Related literature top

For related structures, see: Zhang et al. (2009). For the effects of substituents on the internal angles of the benzene ring, see: Domenicano & Murray-Rust (1979). For NLO and SHG, see: Kurtz & Perry (1968); Kamoun et al. (1995). For ferroelectricity of related compounds, see: Ben Gozlen et al. (1994). For electric and dielectric properties of related compounds, see: Karoui et al. (2013).

Experimental top

Crystals of (C₇H₁₀NO)[SnCl₃] were obtained by dissolving 50 mmol of orthoanisidinium chloride and 50 mmol of stannous chloride in HCl (1M). Metallic tin was added to the obtained solution to avoid the oxidation of Sn(II) to Sn(IV). This solution was then put in desiccators over CaCl₂. After several days, yellow parallelipipedic shaped monocrystals of appeared in the solution. They were collected and washed with diethyl ether. The NLO response of the title compound was measured as follows. A 1064 nm fundamental laser beam emitted by Q-switched Nd³⁺: YAG nanosecond laser (SAGA from Thales Laser) at a 10 Hz repetition rate and a Schott RG 1000 filter were used. The intensity of the incident beam was varied using a half-wave plate rotated between two crossed polarizers. The laser beam was directed onto both samples (KDP: KH₂PO₄ used as reference and C₇H₁₀NO.SnCl₃) oriented at 45° incidence angle relative to the laser beam. The second harmonic signal at 532 nm was collected from the face of the sample at 90° compared with the incident beam. The variation of the second harmonic intensity scattered from KDP or C₇H₁₀NO.SnCl₃ was recorded as a function of the second harmonic reference signal provided by NNP (N-4 nitrophenyl –prolinol) a high NLO material.

Computing details top

Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis RED (Agilent, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg et al., 1999) and Mercury (Macrae et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 2012) and publCIF (Westrip, 2010).

Figures top

	Fig. 1. Perspective view of the title compound with displacement ellipsoids drawn at the 50% probability level and H atoms represented by small spheres of arbitrary radii.
	Fig. 2. The crystal packing of the title compound viewed along the [100] axis showing the hydrogen bonding network.

2-Methoxyanilinium trichloridostannate(II) top

Crystal data top

(C₇H₁₀NO)[SnCl₃]	Cell parameters from 8969 reflections
M_r = 349.20	D_x = 1.977 Mg m⁻³ D_m = 2.010 Mg m⁻³ D_m measured by Flotation
Orthorhombic, P2₁2₁2₁	Melting point: 413 K
Hall symbol: P 2ac 2ab	Mo Kα radiation, λ = 0.71073 Å
a = 7.2030 (2) Å	Cell parameters from 8969 reflections
b = 8.3341 (3) Å	θ = 2.1–27.0°
c = 19.5436 (6) Å	µ = 2.82 mm⁻¹
V = 1173.21 (6) Å³	T = 296 K
Z = 4	Square, yellow
F(000) = 672	0.41 × 0.34 × 0.10 mm

Data collection top

Agilent Xcalibur (Sapphire2) diffractometer	2392 independent reflections
Radiation source: Enhance (Mo) X-ray Source	2236 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.019
Detector resolution: 8.3622 pixels mm^-1	θ_max = 26.4°, θ_min = 3.0°
ω scans	h = −8→9
Absorption correction: multi-scan (CrysAlis RED; Agilent, 2012)	k = −10→9
T_min = 0.391, T_max = 0.765	l = −24→24
8969 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.026	H-atom parameters constrained
wR(F²) = 0.064	w = 1/[σ²(F_o²) + (0.0195P)² + 2.2881P] where P = (F_o² + 2F_c²)/3
S = 1.14	(Δ/σ)_max = 0.001
2392 reflections	Δρ_max = 0.89 e Å⁻³
120 parameters	Δρ_min = −0.69 e Å⁻³
0 restraints	Absolute structure: Flack (1983), 986 Friedel pairs
0 constraints	Absolute structure parameter: 0.03 (5)
Primary atom site location: structure-invariant direct methods

Crystal data top

(C₇H₁₀NO)[SnCl₃]	V = 1173.21 (6) Å³
M_r = 349.20	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 7.2030 (2) Å	µ = 2.82 mm⁻¹
b = 8.3341 (3) Å	T = 296 K
c = 19.5436 (6) Å	0.41 × 0.34 × 0.10 mm

Data collection top

Agilent Xcalibur (Sapphire2) diffractometer	2392 independent reflections
Absorption correction: multi-scan (CrysAlis RED; Agilent, 2012)	2236 reflections with I > 2σ(I)
T_min = 0.391, T_max = 0.765	R_int = 0.019
8969 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.026	H-atom parameters constrained
wR(F²) = 0.064	Δρ_max = 0.89 e Å⁻³
S = 1.14	Δρ_min = −0.69 e Å⁻³
2392 reflections	Absolute structure: Flack (1983), 986 Friedel pairs
120 parameters	Absolute structure parameter: 0.03 (5)
0 restraints

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.

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
Sn1	0.99329 (6)	0.71816 (4)	0.264736 (15)	0.03985 (10)
Cl1	0.74503 (19)	0.88251 (18)	0.20427 (10)	0.0480 (4)
Cl2	0.9729 (2)	0.52707 (13)	0.15669 (5)	0.0476 (3)
Cl3	1.2567 (2)	0.85165 (18)	0.20246 (10)	0.0462 (3)
C1	0.4660 (8)	0.4713 (7)	0.0448 (2)	0.0460 (13)
C2	0.4807 (8)	0.4108 (5)	0.1105 (2)	0.0391 (10)
C3	0.4722 (9)	0.2504 (6)	0.1238 (3)	0.0514 (13)
H3	0.4823	0.2135	0.1686	0.062*
C4	0.4489 (10)	0.1437 (8)	0.0712 (3)	0.068 (2)
H4	0.4431	0.0339	0.0795	0.082*
C5	0.4343 (11)	0.2026 (10)	0.0061 (4)	0.084 (2)
H5	0.4185	0.1308	−0.0298	0.101*
C6	0.4420 (10)	0.3637 (9)	−0.0081 (3)	0.070 (2)
H6	0.4312	0.3999	−0.0529	0.084*
C7	0.4756 (17)	0.7027 (9)	−0.0271 (3)	0.099 (3)
H7A	0.4865	0.8172	−0.0234	0.148*
H7B	0.3612	0.6763	−0.0496	0.148*
H7C	0.5779	0.6615	−0.0533	0.148*
N1	0.5056 (8)	0.5263 (4)	0.16573 (16)	0.0447 (8)
H1A	0.4333	0.6112	0.1584	0.067*
H1B	0.6237	0.5574	0.1672	0.067*
H1C	0.4749	0.4809	0.2054	0.067*
O1	0.4774 (9)	0.6327 (5)	0.03995 (17)	0.0666 (12)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Sn1	0.03921 (16)	0.03849 (15)	0.04186 (16)	−0.00094 (18)	0.0010 (2)	0.00600 (12)
Cl1	0.0361 (6)	0.0544 (8)	0.0536 (9)	0.0062 (6)	−0.0035 (6)	−0.0039 (8)
Cl2	0.0745 (10)	0.0346 (5)	0.0337 (5)	−0.0027 (7)	0.0002 (7)	0.0003 (4)
Cl3	0.0350 (6)	0.0483 (7)	0.0551 (9)	−0.0056 (6)	0.0058 (6)	−0.0033 (7)
C1	0.042 (4)	0.060 (3)	0.036 (2)	0.003 (3)	−0.002 (2)	0.000 (2)
C2	0.035 (3)	0.048 (2)	0.034 (2)	−0.001 (3)	0.006 (2)	−0.0062 (17)
C3	0.057 (4)	0.046 (3)	0.051 (3)	−0.002 (3)	0.010 (3)	−0.003 (2)
C4	0.086 (6)	0.053 (3)	0.067 (4)	−0.011 (3)	0.009 (3)	−0.015 (3)
C5	0.100 (6)	0.093 (6)	0.060 (4)	−0.016 (4)	0.001 (4)	−0.036 (4)
C6	0.083 (5)	0.090 (5)	0.036 (3)	−0.004 (4)	−0.007 (3)	−0.009 (3)
C7	0.151 (8)	0.094 (5)	0.052 (3)	0.018 (8)	−0.002 (6)	0.031 (3)
N1	0.060 (2)	0.0428 (19)	0.0314 (17)	0.004 (3)	0.000 (3)	0.0015 (14)
O1	0.100 (4)	0.061 (2)	0.0394 (18)	0.012 (3)	0.003 (3)	0.0159 (16)

Geometric parameters (Å, º) top

Sn1—Cl1	2.5437 (15)	C4—H4	0.9300
Sn1—Cl2	2.6489 (11)	C5—C6	1.372 (10)
Sn1—Cl3	2.5139 (15)	C5—H5	0.9300
C1—O1	1.351 (6)	C6—H6	0.9300
C1—C6	1.379 (8)	C7—O1	1.435 (6)
C1—C2	1.384 (6)	C7—H7A	0.9600
C2—C3	1.363 (6)	C7—H7B	0.9600
C2—N1	1.458 (5)	C7—H7C	0.9600
C3—C4	1.370 (8)	N1—H1A	0.8900
C3—H3	0.9300	N1—H1B	0.8900
C4—C5	1.367 (10)	N1—H1C	0.8900

Cl3—Sn1—Cl1	93.87 (4)	C6—C5—H5	118.8
Cl3—Sn1—Cl2	85.52 (5)	C5—C6—C1	119.4 (6)
Cl1—Sn1—Cl2	85.10 (5)	C5—C6—H6	120.3
O1—C1—C6	127.1 (5)	C1—C6—H6	120.3
O1—C1—C2	115.0 (4)	O1—C7—H7A	109.5
C6—C1—C2	117.9 (5)	O1—C7—H7B	109.5
C3—C2—C1	122.1 (5)	H7A—C7—H7B	109.5
C3—C2—N1	120.7 (4)	O1—C7—H7C	109.5
C1—C2—N1	117.2 (4)	H7A—C7—H7C	109.5
C2—C3—C4	119.9 (5)	H7B—C7—H7C	109.5
C2—C3—H3	120.1	C2—N1—H1A	109.5
C4—C3—H3	120.1	C2—N1—H1B	109.5
C5—C4—C3	118.3 (6)	H1A—N1—H1B	109.5
C5—C4—H4	120.8	C2—N1—H1C	109.5
C3—C4—H4	120.8	H1A—N1—H1C	109.5
C4—C5—C6	122.4 (6)	H1B—N1—H1C	109.5
C4—C5—H5	118.8	C1—O1—C7	117.9 (5)

O1—C1—C2—C3	−179.9 (6)	C3—C4—C5—C6	0.0 (12)
C6—C1—C2—C3	0.0 (9)	C4—C5—C6—C1	0.2 (12)
O1—C1—C2—N1	0.2 (8)	O1—C1—C6—C5	179.7 (7)
C6—C1—C2—N1	−179.8 (5)	C2—C1—C6—C5	−0.2 (10)
C1—C2—C3—C4	0.2 (10)	C6—C1—O1—C7	−4.0 (12)
N1—C2—C3—C4	−180.0 (6)	C2—C1—O1—C7	176.0 (7)
C2—C3—C4—C5	−0.1 (10)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1C···Cl1ⁱ	0.89	2.51	3.339 (4)	155
N1—H1C···Cl3ⁱⁱ	0.89	2.85	3.418 (4)	123
N1—H1A···Cl3ⁱⁱⁱ	0.89	2.53	3.329 (4)	151
N1—H1B···Cl2	0.89	2.54	3.371 (6)	157
N1—H1B···Cl1	0.89	2.94	3.515 (4)	124
N1—H1A···O1	0.89	2.34	2.621 (5)	98

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

Experimental details

Crystal data
Chemical formula	(C₇H₁₀NO)[SnCl₃]
M_r	349.20
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	296
a, b, c (Å)	7.2030 (2), 8.3341 (3), 19.5436 (6)
V (Å³)	1173.21 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	2.82
Crystal size (mm)	0.41 × 0.34 × 0.10

Data collection
Diffractometer	Agilent Xcalibur (Sapphire2) diffractometer
Absorption correction	Multi-scan (CrysAlis RED; Agilent, 2012)
T_min, T_max	0.391, 0.765
No. of measured, independent and observed [I > 2σ(I)] reflections	8969, 2392, 2236
R_int	0.019
(sin θ/λ)_max (Å⁻¹)	0.625

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.026, 0.064, 1.14
No. of reflections	2392
No. of parameters	120
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.89, −0.69
Absolute structure	Flack (1983), 986 Friedel pairs
Absolute structure parameter	0.03 (5)

Computer programs: CrysAlis PRO (Agilent, 2012), CrysAlis RED (Agilent, 2012), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg et al., 1999) and Mercury (Macrae et al., 2006), WinGX (Farrugia, 2012) and publCIF (Westrip, 2010).

Selected bond lengths (Å) top

Sn1—Cl1	2.5437 (15)	Sn1—Cl3	2.5139 (15)
Sn1—Cl2	2.6489 (11)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1C···Cl1ⁱ	0.89	2.51	3.339 (4)	155.2
N1—H1C···Cl3ⁱⁱ	0.89	2.85	3.418 (4)	122.8
N1—H1A···Cl3ⁱⁱⁱ	0.89	2.53	3.329 (4)	150.5
N1—H1B···Cl2	0.89	2.54	3.371 (6)	156.5
N1—H1B···Cl1	0.89	2.94	3.515 (4)	124.1

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

Acknowledgements

The authors gratefully acknowledge the support of the Tunisian Ministry of Higher Education and Scientific Research and would like to thank I. Ledoux Rak for her support in the second harmonic generation tests.

References

Agilent (2012). CrysAlis PRO and CrysAlis RED. Agilent Technologies, Yarnton, England. Google Scholar
Ben Gozlen, M. H., Kamoun, S., Paulush, H. & Pabst, I. (1994). Z. Kristallogr. 209, 382–382. Google Scholar
Brandenburg, K. & Berndt, M. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Domenicano, A. & Murray-Rust, P. (1979). Tetrahedron Lett. 20, 2283–2286. CrossRef Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Flack, H. D. (1983). Acta Cryst. A39, 876–881. CrossRef CAS Web of Science IUCr Journals Google Scholar
Kamoun, S., Daoud, A., Elfakir, A., Quarton, M. & Ledoux, I. (1995). Solid State Commun. 94, 893–897. CrossRef CAS Web of Science Google Scholar
Karoui, S., Kamoun, S. & Jouini, A. (2013). J. Solid State Chem. 197, 60–68. Web of Science CSD CrossRef CAS Google Scholar
Kurtz, S. K. & Perry, T. T. (1968). J. Appl. Phys. 39, 798–3813. CrossRef Web of Science Google Scholar
Macrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor, R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453–457. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Zhang, S. J., Lanty, G., Lauret, J. S., Deleporte, E., Audebert, P. & Galmiche, L. (2009). Acta Mater. 57, 3301–3309. Web of Science CrossRef CAS Google Scholar