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Acta Crystallogr Sect E Struct Rep Online. 2010 February 1; 66(Pt 2): o262.
Published online 2010 January 9. doi:  10.1107/S1600536809054713
PMCID: PMC2979921

1-Dichloro­acetyl-r-2,c-6-bis­(4-methoxy­phen­yl)-t-3-methyl­piperidin-4-one

Abstract

In the title compound, C22H23Cl2NO4, the piperidine ring adopts a distorted boat conformation. The meth­oxy groups lie in the plane of the benzene rings to which they are attached. The benzene rings are oriented at angles of 84.3 (1) and 76.8 (1)° with respect to the best plane through the piperidine ring. The crystal packing is stabilized by intermolecular C—H(...)O inter­actions.

Related literature

For general background to piperidine derivatives, see: Perumal et al. (2001 [triangle]); Dimmock et al. (2001 [triangle]). For asymmetry parameters, see: Nardelli (1983 [triangle]). For puckering parameters, see: Cremer & Pople (1975 [triangle]). For hydrogen-bond motifs, see: Bernstein et al. (1995 [triangle]).

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Object name is e-66-0o262-scheme1.jpg

Experimental

Crystal data

  • C22H23Cl2NO4
  • M r = 436.31
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-0o262-efi1.jpg
  • a = 19.3021 (16) Å
  • b = 10.5886 (9) Å
  • c = 10.3241 (10) Å
  • β = 91.445 (5)°
  • V = 2109.4 (3) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.34 mm−1
  • T = 293 K
  • 0.25 × 0.24 × 0.23 mm

Data collection

  • Bruker SMART APEXII area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2008 [triangle]) T min = 0.919, T max = 0.926
  • 17272 measured reflections
  • 5140 independent reflections
  • 2632 reflections with I > 2σ(I)
  • R int = 0.050

Refinement

  • R[F 2 > 2σ(F 2)] = 0.055
  • wR(F 2) = 0.210
  • S = 1.05
  • 5140 reflections
  • 265 parameters
  • H-atom parameters constrained
  • Δρmax = 0.37 e Å−3
  • Δρmin = −0.34 e Å−3

Data collection: APEX2 (Bruker, 2008 [triangle]); cell refinement: SAINT (Bruker, 2008 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 (Farrugia, 1997 [triangle]); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809054713/bt5145sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809054713/bt5145Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

KR thanks the GNR X-ray Facility, CAS in Crystallography and Biophysics, University of Madras, India, for the data collection and the management of Kandaswami Kandar’s College, Velur, Namakkal, TN, India, for the encouragement to pursue the programme.

supplementary crystallographic information

Comment

Piperidine derivatives are the valued heterocyclic compounds in the field of medicinal chemistry. piperidin-4-ones are reported to possess analgesic, anti-inflammatory, central nervous system (CNS), local anaesthetic, anticancer and antimicrobial activity (Perumal et al. (2001); Dimmock et al., 2001). The crystallographic study of the title compound has been carried out to establish the molecular structure

The ORTEP diagram of the title compound is shown in Fig.1. The piperidine ring in the molecule adopts a distorted boat conformation with the puckering parameters (Cremer & Pople, 1975) and the asymmetry parameters (Nardelli, 1983) are: q2 = 0.685 (3) Å, q3 = 0.039 (3) Å, [var phi]2 = 72.1 (3)° and Δs(C2 & C5)= 14.9 (3)°. The methoxy groups lie in the plane of phenyl rings and these phenyl rings are oriented at angles of 84.3 (1)° and 76.8 (1)° with best plane of piperidine ring.The sum of the bond angles around the atom N1(359.7°) of the piperidine ring in the molecule is in accordance with sp2 hybridization.

The crystal packing is stabilized by C—H···O types of intra and intermolecular interactions, which link the molecules into a chain extending along the c axis. Atoms C6, C18 and C4 of the molecule at (x, y, z) donate a proton to trifurcated acceptor atom O1 of the molecule at (x, 1/2 - y, -1/2 + z). Intermolecular interactions C6—H6···O1 and C18—H18···O1 form C5 & C7 zigzag chains (Bernstein et al., 1995), whereas the other interaction C8—H8···O1 forms a C4 one-dimensional chain, running along the c axis, as shown in Fig. 2.

Experimental

To a solution of r-2,c-6-bis(4-methoxyphenyl)-t-3-methylpiperidin-4-one (1.625 g) in anhydrous benzene (60 ml) was added triethylamine (2.1 ml) and dichloroacetylchloride (1.42 ml). The reaction mixture was allowed to stirr at room teperature for 2hrs. The resulting solution was washed with sodium bicarbonate solution (10%) and water. The organic layer was dried over anhydrous sodium sulfate, evaporated and crystallized from benzene: pet-ether (60–80°C) in the ratio of 9:1.

Refinement

H atoms were positioned geometrically (C—H=0.93–0.98 Å) and allowed to ride on their parent atoms, with 1.5Ueq(C) for methyl H and 1.2 Ueq(C) for other H atoms.

Figures

Fig. 1.
Perspective view of the molecule showing the thermal ellipsoids are drawn at 30% probability level. H atoms have been omitted for clarity.
Fig. 2.
The crystal packing of the molecules viewed down a–axis. H atoms not involved in hydrogen bonding have been omitted for clarity.

Crystal data

C22H23Cl2NO4F(000) = 912
Mr = 436.31Dx = 1.374 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 2564 reflections
a = 19.3021 (16) Åθ = 1.1–28.7°
b = 10.5886 (9) ŵ = 0.34 mm1
c = 10.3241 (10) ÅT = 293 K
β = 91.445 (5)°Block, colorless
V = 2109.4 (3) Å30.25 × 0.24 × 0.23 mm
Z = 4

Data collection

Bruker SMART APEXII area-detector diffractometer5140 independent reflections
Radiation source: fine-focus sealed tube2632 reflections with I > 2σ(I)
graphiteRint = 0.050
ω and [var phi] scansθmax = 28.7°, θmin = 1.1°
Absorption correction: multi-scan (SADABS; Bruker, 2008)h = −25→25
Tmin = 0.919, Tmax = 0.926k = −13→14
17272 measured reflectionsl = −13→10

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.055Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.210H-atom parameters constrained
S = 1.05w = 1/[σ2(Fo2) + (0.1035P)2 + 0.3613P] where P = (Fo2 + 2Fc2)/3
5140 reflections(Δ/σ)max = 0.001
265 parametersΔρmax = 0.37 e Å3
0 restraintsΔρmin = −0.34 e Å3

Special details

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)

xyzUiso*/Ueq
Cl10.06236 (4)0.37763 (8)0.02208 (10)0.0600 (3)
Cl20.10261 (5)0.12850 (8)−0.06850 (10)0.0618 (3)
O10.18680 (12)0.2296 (2)0.1496 (2)0.0611 (7)
O20.37098 (13)0.6870 (3)0.4740 (3)0.0714 (8)
O30.43242 (15)0.3729 (4)−0.1711 (4)0.1125 (13)
O40.06912 (12)0.8442 (2)−0.1071 (3)0.0607 (7)
N10.24905 (12)0.3470 (2)0.0117 (2)0.0378 (6)
C20.31270 (15)0.3183 (3)0.0888 (3)0.0433 (8)
H20.30250.24220.13880.052*
C30.36826 (17)0.2806 (3)−0.0059 (4)0.0568 (9)
H3A0.41100.26330.04230.068*
H3B0.35410.2032−0.04930.068*
C40.38194 (18)0.3784 (4)−0.1054 (4)0.0617 (10)
C50.32820 (16)0.4799 (3)−0.1204 (3)0.0481 (8)
H50.33640.5402−0.04960.058*
C60.25383 (14)0.4284 (3)−0.1064 (3)0.0379 (7)
H60.24310.3755−0.18210.046*
C70.19106 (15)0.2871 (3)0.0469 (3)0.0407 (7)
C80.12870 (15)0.2872 (3)−0.0465 (3)0.0413 (7)
H80.14160.3238−0.12970.050*
C90.33116 (14)0.4193 (3)0.1869 (3)0.0424 (7)
C100.28014 (16)0.4676 (3)0.2662 (3)0.0502 (8)
H100.23480.43930.25480.060*
C110.29471 (17)0.5556 (4)0.3605 (3)0.0562 (9)
H110.25950.58630.41170.067*
C120.36200 (18)0.5987 (3)0.3792 (3)0.0530 (9)
C130.41367 (17)0.5519 (4)0.3030 (4)0.0584 (10)
H130.45910.57950.31510.070*
C140.39748 (16)0.4635 (4)0.2082 (3)0.0543 (9)
H140.43270.43280.15710.065*
C150.4393 (2)0.7283 (4)0.5030 (5)0.0878 (14)
H15A0.46780.65690.52550.132*
H15B0.43890.78630.57440.132*
H15C0.45770.76980.42860.132*
C160.3347 (2)0.5526 (4)−0.2460 (4)0.0691 (11)
H16A0.38210.5770−0.25660.104*
H16B0.30610.6267−0.24360.104*
H16C0.31990.5001−0.31730.104*
C170.20227 (14)0.5359 (3)−0.1064 (3)0.0348 (7)
C180.15426 (15)0.5514 (3)−0.2067 (3)0.0399 (7)
H180.15290.4928−0.27380.048*
C190.10828 (16)0.6511 (3)−0.2103 (3)0.0428 (7)
H190.07590.6581−0.27810.051*
C200.11057 (16)0.7406 (3)−0.1126 (3)0.0425 (7)
C210.15861 (16)0.7270 (3)−0.0128 (3)0.0456 (8)
H210.16080.78710.05280.055*
C220.20341 (16)0.6263 (3)−0.0083 (3)0.0419 (7)
H220.23480.61830.06100.050*
C230.0234 (2)0.8678 (3)−0.2145 (5)0.0703 (11)
H23A0.04970.8761−0.29170.105*
H23B−0.00180.9444−0.19990.105*
H23C−0.00850.7987−0.22430.105*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Cl10.0590 (5)0.0573 (5)0.0641 (7)0.0081 (4)0.0103 (4)0.0020 (4)
Cl20.0749 (6)0.0441 (5)0.0665 (7)−0.0149 (4)0.0003 (5)−0.0053 (4)
O10.0674 (15)0.0703 (16)0.0452 (15)−0.0148 (12)−0.0051 (12)0.0270 (13)
O20.0731 (17)0.0837 (18)0.0570 (18)−0.0107 (14)−0.0054 (14)−0.0164 (15)
O30.0646 (18)0.161 (3)0.114 (3)0.0281 (19)0.0481 (19)0.042 (2)
O40.0657 (15)0.0398 (12)0.076 (2)0.0079 (11)−0.0022 (14)−0.0061 (12)
N10.0424 (13)0.0422 (14)0.0288 (15)0.0000 (11)0.0011 (11)0.0049 (11)
C20.0434 (17)0.0500 (18)0.037 (2)0.0071 (14)−0.0012 (14)0.0052 (15)
C30.0512 (19)0.068 (2)0.051 (2)0.0129 (17)0.0018 (16)−0.0085 (19)
C40.0458 (19)0.088 (3)0.052 (2)−0.0024 (18)0.0091 (17)−0.006 (2)
C50.0497 (18)0.058 (2)0.037 (2)−0.0090 (15)0.0100 (14)−0.0009 (16)
C60.0457 (16)0.0459 (17)0.0223 (16)−0.0058 (13)0.0028 (12)−0.0004 (13)
C70.0467 (17)0.0386 (16)0.0367 (19)−0.0007 (13)0.0002 (14)0.0030 (14)
C80.0463 (16)0.0394 (15)0.0382 (19)−0.0059 (13)0.0011 (14)0.0018 (13)
C90.0397 (16)0.0568 (19)0.0307 (18)0.0009 (14)−0.0018 (13)0.0029 (15)
C100.0420 (17)0.068 (2)0.041 (2)−0.0006 (15)−0.0010 (14)−0.0059 (17)
C110.0478 (19)0.077 (2)0.043 (2)0.0032 (17)0.0017 (15)−0.0102 (19)
C120.060 (2)0.065 (2)0.033 (2)−0.0035 (17)−0.0043 (16)−0.0014 (17)
C130.0459 (19)0.083 (3)0.046 (2)−0.0115 (18)−0.0030 (16)0.001 (2)
C140.0411 (17)0.083 (3)0.038 (2)−0.0005 (17)0.0037 (14)−0.0004 (19)
C150.086 (3)0.098 (3)0.078 (3)−0.025 (3)−0.013 (3)−0.022 (3)
C160.079 (3)0.078 (3)0.051 (3)−0.019 (2)0.019 (2)0.010 (2)
C170.0474 (16)0.0344 (15)0.0228 (16)−0.0052 (12)0.0054 (12)0.0021 (12)
C180.0579 (18)0.0344 (15)0.0276 (18)−0.0022 (13)0.0029 (14)−0.0015 (13)
C190.0543 (18)0.0383 (16)0.0356 (19)−0.0048 (13)−0.0026 (14)0.0099 (14)
C200.0512 (17)0.0336 (16)0.043 (2)−0.0036 (13)0.0078 (15)0.0030 (14)
C210.0567 (18)0.0443 (17)0.036 (2)−0.0033 (15)0.0074 (15)−0.0106 (15)
C220.0478 (17)0.0485 (18)0.0294 (18)−0.0010 (14)−0.0010 (13)−0.0004 (14)
C230.068 (2)0.051 (2)0.090 (3)0.0093 (18)−0.012 (2)0.014 (2)

Geometric parameters (Å, °)

Cl1—C81.762 (3)C10—C111.372 (5)
Cl2—C81.768 (3)C10—H100.9300
O1—C71.228 (4)C11—C121.385 (4)
O2—C121.362 (4)C11—H110.9300
O2—C151.415 (4)C12—C131.378 (5)
O3—C41.203 (4)C13—C141.383 (5)
O4—C201.360 (4)C13—H130.9300
O4—C231.422 (4)C14—H140.9300
N1—C71.344 (4)C15—H15A0.9600
N1—C21.479 (4)C15—H15B0.9600
N1—C61.498 (4)C15—H15C0.9600
C2—C91.509 (4)C16—H16A0.9600
C2—C31.523 (4)C16—H16B0.9600
C2—H20.9800C16—H16C0.9600
C3—C41.487 (5)C17—C181.382 (4)
C3—H3A0.9700C17—C221.394 (4)
C3—H3B0.9700C18—C191.379 (4)
C4—C51.499 (5)C18—H180.9300
C5—C161.516 (5)C19—C201.384 (4)
C5—C61.546 (4)C19—H190.9300
C5—H50.9800C20—C211.377 (4)
C6—C171.512 (4)C21—C221.372 (4)
C6—H60.9800C21—H210.9300
C7—C81.523 (4)C22—H220.9300
C8—H80.9800C23—H23A0.9600
C9—C141.375 (4)C23—H23B0.9600
C9—C101.393 (4)C23—H23C0.9600
C12—O2—C15117.7 (3)C10—C11—H11120.1
C20—O4—C23117.6 (3)C12—C11—H11120.1
C7—N1—C2116.4 (2)O2—C12—C13125.2 (3)
C7—N1—C6124.0 (2)O2—C12—C11115.3 (3)
C2—N1—C6119.3 (2)C13—C12—C11119.4 (3)
N1—C2—C9113.3 (2)C12—C13—C14119.5 (3)
N1—C2—C3107.3 (3)C12—C13—H13120.2
C9—C2—C3117.3 (3)C14—C13—H13120.2
N1—C2—H2106.1C9—C14—C13122.4 (3)
C9—C2—H2106.1C9—C14—H14118.8
C3—C2—H2106.1C13—C14—H14118.8
C4—C3—C2113.6 (3)O2—C15—H15A109.5
C4—C3—H3A108.8O2—C15—H15B109.5
C2—C3—H3A108.8H15A—C15—H15B109.5
C4—C3—H3B108.8O2—C15—H15C109.5
C2—C3—H3B108.8H15A—C15—H15C109.5
H3A—C3—H3B107.7H15B—C15—H15C109.5
O3—C4—C3121.1 (4)C5—C16—H16A109.5
O3—C4—C5123.0 (4)C5—C16—H16B109.5
C3—C4—C5115.9 (3)H16A—C16—H16B109.5
C4—C5—C16112.4 (3)C5—C16—H16C109.5
C4—C5—C6112.3 (3)H16A—C16—H16C109.5
C16—C5—C6110.9 (3)H16B—C16—H16C109.5
C4—C5—H5107.0C18—C17—C22117.5 (3)
C16—C5—H5107.0C18—C17—C6121.2 (3)
C6—C5—H5107.0C22—C17—C6121.3 (3)
N1—C6—C17112.3 (2)C19—C18—C17122.0 (3)
N1—C6—C5110.8 (2)C19—C18—H18119.0
C17—C6—C5110.3 (2)C17—C18—H18119.0
N1—C6—H6107.7C18—C19—C20119.7 (3)
C17—C6—H6107.7C18—C19—H19120.1
C5—C6—H6107.7C20—C19—H19120.1
O1—C7—N1122.8 (3)O4—C20—C21116.0 (3)
O1—C7—C8118.6 (3)O4—C20—C19125.1 (3)
N1—C7—C8118.6 (3)C21—C20—C19118.9 (3)
C7—C8—Cl1108.5 (2)C22—C21—C20121.3 (3)
C7—C8—Cl2107.4 (2)C22—C21—H21119.4
Cl1—C8—Cl2111.14 (16)C20—C21—H21119.4
C7—C8—H8109.9C21—C22—C17120.7 (3)
Cl1—C8—H8109.9C21—C22—H22119.7
Cl2—C8—H8109.9C17—C22—H22119.7
C14—C9—C10116.7 (3)O4—C23—H23A109.5
C14—C9—C2123.5 (3)O4—C23—H23B109.5
C10—C9—C2119.7 (3)H23A—C23—H23B109.5
C11—C10—C9122.1 (3)O4—C23—H23C109.5
C11—C10—H10119.0H23A—C23—H23C109.5
C9—C10—H10119.0H23B—C23—H23C109.5
C10—C11—C12119.8 (3)
C7—N1—C2—C9−101.3 (3)N1—C2—C9—C1046.9 (4)
C6—N1—C2—C984.8 (3)C3—C2—C9—C10172.8 (3)
C7—N1—C2—C3127.6 (3)C14—C9—C10—C110.5 (5)
C6—N1—C2—C3−46.3 (3)C2—C9—C10—C11177.3 (3)
N1—C2—C3—C457.2 (4)C9—C10—C11—C12−0.2 (6)
C9—C2—C3—C4−71.6 (4)C15—O2—C12—C13−4.4 (6)
C2—C3—C4—O3166.1 (4)C15—O2—C12—C11176.0 (3)
C2—C3—C4—C5−15.7 (4)C10—C11—C12—O2179.3 (3)
O3—C4—C5—C1614.5 (5)C10—C11—C12—C13−0.3 (6)
C3—C4—C5—C16−163.6 (3)O2—C12—C13—C14−179.0 (3)
O3—C4—C5—C6140.2 (4)C11—C12—C13—C140.6 (6)
C3—C4—C5—C6−37.8 (4)C10—C9—C14—C13−0.2 (5)
C7—N1—C6—C1757.7 (4)C2—C9—C14—C13−176.9 (3)
C2—N1—C6—C17−128.9 (3)C12—C13—C14—C9−0.3 (6)
C7—N1—C6—C5−178.4 (3)N1—C6—C17—C18−122.7 (3)
C2—N1—C6—C5−5.1 (4)C5—C6—C17—C18113.1 (3)
C4—C5—C6—N148.3 (4)N1—C6—C17—C2260.2 (3)
C16—C5—C6—N1174.9 (3)C5—C6—C17—C22−64.0 (3)
C4—C5—C6—C17173.3 (3)C22—C17—C18—C19−0.8 (4)
C16—C5—C6—C17−60.1 (3)C6—C17—C18—C19−178.0 (3)
C2—N1—C7—O112.7 (4)C17—C18—C19—C201.4 (4)
C6—N1—C7—O1−173.7 (3)C23—O4—C20—C21174.2 (3)
C2—N1—C7—C8−165.4 (3)C23—O4—C20—C19−5.0 (4)
C6—N1—C7—C88.2 (4)C18—C19—C20—O4178.5 (3)
O1—C7—C8—Cl169.3 (3)C18—C19—C20—C21−0.7 (4)
N1—C7—C8—Cl1−112.5 (3)O4—C20—C21—C22−179.8 (3)
O1—C7—C8—Cl2−50.9 (3)C19—C20—C21—C22−0.6 (4)
N1—C7—C8—Cl2127.3 (3)C20—C21—C22—C171.2 (4)
N1—C2—C9—C14−136.5 (3)C18—C17—C22—C21−0.5 (4)
C3—C2—C9—C14−10.6 (5)C6—C17—C22—C21176.7 (3)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
C6—H6···O1i0.982.313.264 (4)164
C8—H8···O1i0.982.523.363 (4)144
C18—H18···O1i0.932.573.391 (4)147

Symmetry codes: (i) x, −y+1/2, z−1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT5145).

References

  • Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl.34, 1555–1573.
  • Bruker (2008). APEX2, SAINT and SADABS Bruker AXS Inc., Madison, Wisconsin, USA.
  • Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc.97, 1354–1358.
  • Dimmock, J. R., Padmanilayam, M. P., Puthucode, R. N., Nazarali, A. J., Motaganahalli, N. L., Zello, G. A., Quail, J. W., Oloo, E. O., Kraatz, H. B., Prisciak, J. S., Allen, T. M., Santhos, C. L., Balsarini, J., Clercq, E. D. & Manavathu, E. K. (2001). J. Med. Chem.44, 586–593. [PubMed]
  • Farrugia, L. J. (1997). J. Appl. Cryst.30, 565.
  • Nardelli, M. (1983). Acta Cryst. C39, 1141–1142.
  • Perumal, R. V., Adiraj, M. & Shanmugapandiyan, P. (2001). Indian Drugs, 38, 156–159
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Spek, A. L. (2009). Acta Cryst. D65, 148–155. [PMC free article] [PubMed]

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