5-(2,3-Di­chloro­phen­yl)-3-(4-meth­oxy­phen­yl)-1-phenyl-4,5-di­hydro-1H-pyrazole

Lokeshwari, D.M.; Naveen, S.; Prabhudeva, M.G.; Raghavendra, K.R.; Dileep Kumar, A.; Lokanath, N.K.; Ajay Kumar, K.

doi:10.1107/S2414314616020137

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 2| Part 1| January 2017| x162013

https://doi.org/10.1107/S2414314616020137

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5-(2,3-Dichlorophenyl)-3-(4-methoxyphenyl)-1-phenyl-4,5-dihydro-1H-pyrazole

D. M. Lokeshwari,^a S. Naveen,^b M. G. Prabhudeva,^a K. R. Raghavendra,^a A. Dileep Kumar,^a N. K. Lokanath ^c ^* and K. Ajay Kumar ^a ^*

^aDepartment of Chemistry, Yuvaraja's College, University of Mysore, Mysuru 570 005, India, ^bInstitution of Excellence, University of Mysore, Manasagangotri, Mysuru 570 006, India, and ^cDepartment of Studies in Physics, University of Mysore, Manasagangotri, Mysuru 570 006, India
^*Correspondence e-mail: lokanath@physics.uni-mysore.ac.in, ajaykumar@ycm.uni-mysore.ac.in

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 16 December 2016; accepted 19 December 2016; online 6 January 2017)

In the racemic title compound, C₂₂H₁₈Cl₂N₂O, the dihedral angles between the central dihydropyrazole ring (r.m.s. deviation = 0.018 Å) and the pendant methoxyphenyl, phenyl and dichlorophenyl rings are 3.96 (9), 15.90 (9) and 66.65 (9)° respectively. Weak aromatic π–π stacking [shortest centroid–centroid separation = 3.8476 (11) Å] occurs in the crystal.

Keywords: crystal structure; pyrazoles; chiral.

CCDC reference: 1523508

Structure description

In continuation of our work on pyrazoline derivatives (Assem et al., 2016 ), we report herein on the synthesis and crystal structure of the title compound. The title molecule is shown in Fig. 1. The pyrazole ring is nearly planar with atom C1 deviating by 0.017 (2) Å from the mean plane defined by atoms N1, N2, C2 and C3. The dihedral angle between the pyrazole ring and the methoxyphenyl ring is 3.96 (9)°, indicating their near coplanarity, whereas those between the pyrazole ring and the phenyl and dichlorophenyl rings are 15.90 (9) and 66.65 (9)°, respectively. In the arbitrarily chosen asymmetric molecule, the compound possess a chiral center at C3 with R conformation. Since the compound crystallizes in a centrosymmetric space group, we can surmise that the compound is a racemic mixture. The torsion angle value of 6.2 (3)° for C10—O1—C—C6 indicates that the methoxy group lies almost in the plane of the phenyl ring. No hydrogen bonds were observed in the crystal but weak aromatic π–π stacking [shortest centroid–centroid separation = 3.8476 (11) Å] is observed.

Figure 1
The molecular structure of the title compound with displacement ellipsoids for non-H atoms drawn at the 50% probability level.

Synthesis and crystallization

To a solution of (E)-3-(2,3-dichlorophenyl)-1-(4-methoxyphenyl)prop-2-en-1-one, (3 mmol) and phenylhydrazine hydrochloride (3 mmol) in methyl alcohol (25 ml), 4–5 drops of conc. hydrochloric acid were added. The mixture was refluxed on a water bath for 4 h. The progress of the reaction was monitored by TLC. After completion, the mixture was poured into ice-cold water and stirred. The solid that separated was filtered and washed with ice-cold water. The product was crystallized from methyl alcohol solution with 2–3 drops of acetonitrile added to get the title compound in the form of yellow blocks in 88% yield, m.p. 134–136°C.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

Table 1
Experimental details

Crystal data
Chemical formula	C₂₂H₁₈Cl₂N₂O
M_r	397.28
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	13.8255 (5), 11.0655 (4), 13.3583 (5)
β (°)	112.972 (1)
V (Å³)	1881.57 (12)
Z	4
Radiation type	Cu Kα
μ (mm⁻¹)	3.21
Crystal size (mm)	0.29 × 0.26 × 0.23

Data collection
Diffractometer	Bruker X8 Proteum
Absorption correction	Multi-scan (SADABS; Bruker, 2013 )
T_min, T_max	0.456, 0.525
No. of measured, independent and observed [I > 2σ(I)] reflections	19112, 3089, 2996
R_int	0.055
(sin θ/λ)_max (Å⁻¹)	0.586

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.116, 1.07
No. of reflections	3089
No. of parameters	246
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.27, −0.31
Computer programs: APEX2 and SAINT (Bruker, 2013), SHELXS and SHELXL (Sheldrick, 2008 ) and Mercury (Macrae et al., 2008 ).

Structural data

CCDC reference: 1523508

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S2414314616020137/hb4106sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314616020137/hb4106Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314616020137/hb4106Isup3.cml

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2013); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS (Sheldrick, 2008); program(s) used to refine structure: SHELXL (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: Mercury (Macrae et al., 2008).

5-(2,3-Dichlorophenyl)-3-(4-methoxyphenyl)-1-phenyl-4,5-dihydro-1H-pyrazole top

Crystal data top

C₂₂H₁₈Cl₂N₂O	F(000) = 824
M_r = 397.28	D_x = 1.403 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: -P 2ybc	Cell parameters from 2996 reflections
a = 13.8255 (5) Å	θ = 5.3–64.6°
b = 11.0655 (4) Å	µ = 3.21 mm⁻¹
c = 13.3583 (5) Å	T = 296 K
β = 112.972 (1)°	Block, yellow
V = 1881.57 (12) Å³	0.29 × 0.26 × 0.23 mm
Z = 4

Data collection top

Bruker X8 Proteum diffractometer	3089 independent reflections
Radiation source: Bruker MicroStar microfocus rotating anode	2996 reflections with I > 2σ(I)
Helios multilayer optics monochromator	R_int = 0.055
Detector resolution: 18.4 pixels mm^-1	θ_max = 64.6°, θ_min = 5.3°
φ and ω scans	h = −15→15
Absorption correction: multi-scan (SADABS; Bruker, 2013)	k = −12→12
T_min = 0.456, T_max = 0.525	l = −13→15
19112 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)] = 0.040	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.116	w = 1/[σ²(F_o²) + (0.0747P)² + 0.6657P] where P = (F_o² + 2F_c²)/3
S = 1.07	(Δ/σ)_max = 0.001
3089 reflections	Δρ_max = 0.27 e Å⁻³
246 parameters	Δρ_min = −0.31 e Å⁻³
0 restraints	Extinction correction: shelxl, FC^*=KFC[1+0.001XFC²Λ³/SIN(2Θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0044 (5)

Special details top

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles

Refinement. Refinement on F² for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > 2sigma(F²) is used only for calculating -R-factor-obs 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
Cl1	0.87473 (3)	0.71246 (4)	0.68752 (3)	0.0315 (2)
Cl2	0.99910 (3)	0.94868 (5)	0.68003 (4)	0.0380 (2)
O1	0.13280 (10)	0.71402 (12)	0.56282 (11)	0.0338 (4)
N1	0.59658 (11)	0.63158 (14)	0.38384 (11)	0.0255 (4)
N2	0.49511 (11)	0.62782 (12)	0.37995 (11)	0.0230 (4)
C1	0.49661 (14)	0.65881 (15)	0.47377 (13)	0.0220 (5)
C2	0.60554 (13)	0.68189 (16)	0.55786 (14)	0.0254 (5)
C3	0.67436 (13)	0.66381 (15)	0.49192 (13)	0.0225 (5)
C4	0.40026 (14)	0.67089 (14)	0.49382 (14)	0.0222 (5)
C5	0.30163 (14)	0.64888 (16)	0.41333 (14)	0.0259 (5)
C6	0.21047 (14)	0.66298 (16)	0.43247 (15)	0.0279 (5)
C7	0.21773 (14)	0.69931 (16)	0.53491 (15)	0.0264 (5)
C8	0.31531 (15)	0.72286 (15)	0.61613 (15)	0.0275 (5)
C9	0.40538 (14)	0.70892 (15)	0.59615 (14)	0.0241 (5)
C10	0.03301 (16)	0.6789 (2)	0.4851 (2)	0.0456 (8)
C11	0.62138 (13)	0.57251 (15)	0.30494 (13)	0.0225 (5)
C12	0.72612 (14)	0.56432 (16)	0.31559 (14)	0.0261 (5)
C13	0.75027 (15)	0.50561 (16)	0.23657 (15)	0.0298 (6)
C14	0.67259 (17)	0.45529 (16)	0.14630 (15)	0.0318 (6)
C15	0.56912 (15)	0.46328 (16)	0.13576 (15)	0.0290 (5)
C16	0.54263 (14)	0.52186 (16)	0.21336 (14)	0.0247 (5)
C17	0.73547 (13)	0.77685 (14)	0.48744 (13)	0.0206 (5)
C18	0.82811 (13)	0.80672 (15)	0.57467 (13)	0.0220 (5)
C19	0.88385 (13)	0.91101 (16)	0.57130 (15)	0.0256 (5)
C20	0.84742 (15)	0.98622 (17)	0.48206 (16)	0.0303 (6)
C21	0.75577 (16)	0.95706 (17)	0.39570 (16)	0.0322 (6)
C22	0.70052 (14)	0.85391 (16)	0.39824 (14)	0.0276 (5)
H2A	0.62370	0.62460	0.61740	0.0300*
H2B	0.61210	0.76340	0.58660	0.0300*
H3	0.72290	0.59630	0.52210	0.0270*
H5	0.29650	0.62410	0.34490	0.0310*
H6	0.14520	0.64830	0.37730	0.0330*
H8	0.32010	0.74810	0.68430	0.0330*
H9	0.47040	0.72490	0.65120	0.0290*
H10A	0.01390	0.73050	0.42250	0.0680*
H10B	−0.01850	0.68590	0.51650	0.0680*
H10C	0.03610	0.59670	0.46380	0.0680*
H12	0.77940	0.59820	0.37560	0.0310*
H13	0.82000	0.50000	0.24450	0.0360*
H14	0.68950	0.41670	0.09340	0.0380*
H15	0.51640	0.42880	0.07560	0.0350*
H16	0.47260	0.52740	0.20450	0.0300*
H20	0.88430	1.05590	0.48010	0.0360*
H21	0.73090	1.00730	0.33510	0.0390*
H22	0.63880	0.83570	0.33920	0.0330*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0323 (3)	0.0271 (3)	0.0258 (3)	−0.0009 (2)	0.0012 (2)	0.0050 (2)
Cl2	0.0264 (3)	0.0396 (3)	0.0438 (3)	−0.0121 (2)	0.0092 (2)	−0.0092 (2)
O1	0.0319 (7)	0.0344 (8)	0.0418 (8)	0.0067 (5)	0.0217 (6)	0.0055 (6)
N1	0.0209 (7)	0.0304 (8)	0.0248 (8)	−0.0046 (6)	0.0084 (6)	−0.0078 (6)
N2	0.0233 (7)	0.0196 (8)	0.0266 (8)	−0.0024 (5)	0.0102 (6)	−0.0008 (6)
C1	0.0264 (9)	0.0153 (8)	0.0244 (9)	−0.0016 (6)	0.0100 (7)	0.0012 (6)
C2	0.0289 (9)	0.0245 (9)	0.0238 (9)	−0.0039 (7)	0.0114 (7)	−0.0021 (7)
C3	0.0227 (8)	0.0208 (9)	0.0216 (8)	−0.0020 (7)	0.0059 (7)	−0.0015 (6)
C4	0.0277 (9)	0.0141 (8)	0.0256 (9)	−0.0017 (6)	0.0112 (7)	0.0023 (6)
C5	0.0303 (9)	0.0229 (9)	0.0252 (9)	−0.0025 (7)	0.0117 (7)	−0.0011 (7)
C6	0.0259 (9)	0.0238 (9)	0.0332 (10)	−0.0023 (7)	0.0108 (7)	0.0014 (7)
C7	0.0297 (9)	0.0180 (9)	0.0357 (10)	0.0045 (7)	0.0175 (8)	0.0071 (7)
C8	0.0375 (10)	0.0211 (9)	0.0272 (9)	0.0037 (7)	0.0162 (8)	0.0027 (7)
C9	0.0283 (9)	0.0191 (9)	0.0240 (9)	−0.0005 (7)	0.0094 (7)	0.0024 (6)
C10	0.0312 (11)	0.0472 (13)	0.0647 (15)	−0.0029 (9)	0.0257 (10)	−0.0080 (11)
C11	0.0296 (9)	0.0157 (8)	0.0241 (9)	−0.0016 (6)	0.0125 (7)	0.0008 (6)
C12	0.0287 (9)	0.0208 (9)	0.0285 (9)	−0.0032 (7)	0.0109 (7)	−0.0015 (7)
C13	0.0353 (10)	0.0230 (9)	0.0376 (10)	0.0020 (7)	0.0214 (8)	0.0031 (8)
C14	0.0483 (11)	0.0225 (10)	0.0316 (10)	0.0017 (8)	0.0231 (9)	−0.0003 (7)
C15	0.0415 (10)	0.0197 (9)	0.0235 (9)	−0.0034 (7)	0.0103 (8)	−0.0008 (7)
C16	0.0287 (9)	0.0188 (9)	0.0255 (9)	−0.0014 (7)	0.0093 (7)	0.0011 (7)
C17	0.0224 (8)	0.0167 (8)	0.0236 (9)	0.0008 (6)	0.0101 (7)	−0.0022 (6)
C18	0.0230 (8)	0.0188 (8)	0.0245 (9)	0.0018 (7)	0.0095 (7)	−0.0003 (7)
C19	0.0220 (8)	0.0233 (9)	0.0326 (9)	−0.0024 (7)	0.0119 (7)	−0.0063 (7)
C20	0.0363 (10)	0.0192 (9)	0.0410 (11)	−0.0041 (7)	0.0211 (9)	−0.0012 (8)
C21	0.0437 (11)	0.0233 (10)	0.0330 (10)	0.0041 (8)	0.0188 (9)	0.0071 (7)
C22	0.0296 (9)	0.0248 (9)	0.0254 (9)	0.0034 (7)	0.0074 (7)	0.0012 (7)

Geometric parameters (Å, º) top

Cl1—C18	1.7371 (17)	C17—C18	1.394 (2)
Cl2—C19	1.7366 (19)	C17—C22	1.390 (2)
O1—C7	1.373 (3)	C18—C19	1.398 (3)
O1—C10	1.419 (3)	C19—C20	1.378 (3)
N1—N2	1.384 (2)	C20—C21	1.378 (3)
N1—C3	1.468 (2)	C21—C22	1.381 (3)
N1—C11	1.392 (2)	C2—H2A	0.9700
N2—C1	1.292 (2)	C2—H2B	0.9700
C1—C2	1.508 (3)	C3—H3	0.9800
C1—C4	1.464 (3)	C5—H5	0.9300
C2—C3	1.541 (3)	C6—H6	0.9300
C3—C17	1.524 (2)	C8—H8	0.9300
C4—C5	1.389 (3)	C9—H9	0.9300
C4—C9	1.405 (2)	C10—H10A	0.9600
C5—C6	1.389 (3)	C10—H10B	0.9600
C6—C7	1.392 (3)	C10—H10C	0.9600
C7—C8	1.387 (3)	C12—H12	0.9300
C8—C9	1.380 (3)	C13—H13	0.9300
C11—C12	1.402 (3)	C14—H14	0.9300
C11—C16	1.399 (2)	C15—H15	0.9300
C12—C13	1.387 (3)	C16—H16	0.9300
C13—C14	1.381 (3)	C20—H20	0.9300
C14—C15	1.385 (3)	C21—H21	0.9300
C15—C16	1.388 (3)	C22—H22	0.9300

C7—O1—C10	117.32 (16)	C20—C21—C22	120.63 (18)
N2—N1—C3	112.76 (13)	C17—C22—C21	121.17 (17)
N2—N1—C11	120.20 (14)	C1—C2—H2A	111.00
C3—N1—C11	123.80 (15)	C1—C2—H2B	111.00
N1—N2—C1	108.87 (15)	C3—C2—H2A	111.00
N2—C1—C2	113.63 (17)	C3—C2—H2B	111.00
N2—C1—C4	122.05 (16)	H2A—C2—H2B	109.00
C2—C1—C4	124.32 (15)	N1—C3—H3	110.00
C1—C2—C3	102.25 (14)	C2—C3—H3	110.00
N1—C3—C2	102.41 (14)	C17—C3—H3	110.00
N1—C3—C17	111.43 (13)	C4—C5—H5	119.00
C2—C3—C17	113.04 (14)	C6—C5—H5	119.00
C1—C4—C5	122.06 (16)	C5—C6—H6	120.00
C1—C4—C9	120.09 (17)	C7—C6—H6	120.00
C5—C4—C9	117.83 (18)	C7—C8—H8	120.00
C4—C5—C6	121.66 (17)	C9—C8—H8	120.00
C5—C6—C7	119.40 (18)	C4—C9—H9	120.00
O1—C7—C6	124.05 (18)	C8—C9—H9	120.00
O1—C7—C8	116.05 (17)	O1—C10—H10A	109.00
C6—C7—C8	119.90 (19)	O1—C10—H10B	109.00
C7—C8—C9	120.23 (17)	O1—C10—H10C	109.00
C4—C9—C8	120.98 (18)	H10A—C10—H10B	109.00
N1—C11—C12	120.23 (15)	H10A—C10—H10C	110.00
N1—C11—C16	120.84 (17)	H10B—C10—H10C	109.00
C12—C11—C16	118.92 (16)	C11—C12—H12	120.00
C11—C12—C13	119.95 (17)	C13—C12—H12	120.00
C12—C13—C14	121.2 (2)	C12—C13—H13	119.00
C13—C14—C15	118.93 (19)	C14—C13—H13	119.00
C14—C15—C16	121.16 (18)	C13—C14—H14	121.00
C11—C16—C15	119.89 (19)	C15—C14—H14	121.00
C3—C17—C18	120.30 (14)	C14—C15—H15	119.00
C3—C17—C22	121.66 (16)	C16—C15—H15	119.00
C18—C17—C22	118.03 (16)	C11—C16—H16	120.00
Cl1—C18—C17	119.46 (13)	C15—C16—H16	120.00
Cl1—C18—C19	120.07 (13)	C19—C20—H20	120.00
C17—C18—C19	120.47 (15)	C21—C20—H20	120.00
Cl2—C19—C18	120.57 (14)	C20—C21—H21	120.00
Cl2—C19—C20	119.00 (15)	C22—C21—H21	120.00
C18—C19—C20	120.43 (17)	C17—C22—H22	119.00
C19—C20—C21	119.27 (18)	C21—C22—H22	119.00

C10—O1—C7—C6	6.2 (3)	C5—C4—C9—C8	0.6 (2)
C10—O1—C7—C8	−173.76 (16)	C4—C5—C6—C7	−0.4 (3)
C3—N1—N2—C1	2.39 (19)	C5—C6—C7—O1	−178.90 (16)
C11—N1—N2—C1	162.79 (15)	C5—C6—C7—C8	1.0 (3)
N2—N1—C3—C2	−0.60 (17)	O1—C7—C8—C9	179.10 (15)
N2—N1—C3—C17	−121.72 (16)	C6—C7—C8—C9	−0.8 (3)
C11—N1—C3—C2	−160.19 (15)	C7—C8—C9—C4	0.0 (3)
C11—N1—C3—C17	78.7 (2)	N1—C11—C12—C13	−179.84 (16)
N2—N1—C11—C12	−172.59 (15)	C16—C11—C12—C13	−0.7 (3)
N2—N1—C11—C16	8.2 (2)	N1—C11—C16—C15	−179.93 (16)
C3—N1—C11—C12	−14.4 (2)	C12—C11—C16—C15	0.9 (3)
C3—N1—C11—C16	166.39 (16)	C11—C12—C13—C14	0.5 (3)
N1—N2—C1—C2	−3.22 (19)	C12—C13—C14—C15	−0.5 (3)
N1—N2—C1—C4	176.18 (14)	C13—C14—C15—C16	0.8 (3)
N2—C1—C2—C3	2.73 (19)	C14—C15—C16—C11	−0.9 (3)
C4—C1—C2—C3	−176.64 (15)	C3—C17—C18—Cl1	1.2 (2)
N2—C1—C4—C5	0.5 (3)	C3—C17—C18—C19	−179.37 (17)
N2—C1—C4—C9	−177.78 (16)	C22—C17—C18—Cl1	−179.76 (14)
C2—C1—C4—C5	179.80 (16)	C22—C17—C18—C19	−0.4 (3)
C2—C1—C4—C9	1.6 (2)	C3—C17—C22—C21	179.07 (18)
C1—C2—C3—N1	−1.10 (16)	C18—C17—C22—C21	0.1 (3)
C1—C2—C3—C17	118.90 (15)	Cl1—C18—C19—Cl2	−0.8 (2)
N1—C3—C17—C18	−165.11 (16)	Cl1—C18—C19—C20	179.97 (15)
N1—C3—C17—C22	15.9 (2)	C17—C18—C19—Cl2	179.82 (14)
C2—C3—C17—C18	80.2 (2)	C17—C18—C19—C20	0.6 (3)
C2—C3—C17—C22	−98.77 (19)	Cl2—C19—C20—C21	−179.74 (16)
C1—C4—C5—C6	−178.66 (16)	C18—C19—C20—C21	−0.5 (3)
C9—C4—C5—C6	−0.4 (3)	C19—C20—C21—C22	0.2 (3)
C1—C4—C9—C8	178.89 (15)	C20—C21—C22—C17	0.0 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C16—H16···N2	0.93	2.50	2.811 (2)	100
C22—H22···N1	0.93	2.46	2.818 (2)	103

Acknowledgements

The authors are grateful to the Institution of Excellence, Vijnana Bhavana, University of Mysore, India, for providing the single-crystal X-ray diffractometer facility.

References

Assem, B., Naveen, S., Nagamallu, R., Ajay Kumar, K., Abdoh, M., Warad, I. & Lokanath, N. K. (2016). Z. Kristallogr, 231, 267–269. Google Scholar
Bruker (2013). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. 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 CSD CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar

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