PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of actaeInternational Union of Crystallographysearchopen accessarticle submissionjournal home pagethis article
 
Acta Crystallogr Sect E Struct Rep Online. 2010 March 1; 66(Pt 3): o574.
Published online 2010 February 10. doi:  10.1107/S1600536810004368
PMCID: PMC2983701

7-(4-Bromo­phen­yl)-9-phenyl-7H-pyrrolo[3,2-e]tetra­zolo[1,5-c]pyrimidine

Abstract

In the title compound, C18H11BrN6, the phenyl ring is almost coplanar [dihedral angle 7.2 (1)°] with the planar (r.m.s. deviation 0.039 Å) tricyclic ring system while the 4-bromo­phenyl ring makes a dihedral angle of 33.98 (6)° with the ring system. Weak inter­molecular C—H(...)N and C—H(...)Br hydrogen-bonding inter­actions and π–π stacking [centroid–centroid distances = 3.7971 (17) and 3.5599 (16) Å] stabilize the crystal packing. A comparison of the structure to a MOPAC PM3 geometry optimization calculation in vacuo supports these observations.

Related literature

For anti­cancer relationships, see: Hiedo & Yasuo (1960 [triangle], 1961 [triangle]). For the synthesis of derivative compounds, see: Dave & Shukla (1997 [triangle]); Dave & Shah (1998 [triangle]). For graph-set motifs, see: Bernstein et al. (1995 [triangle]). For MOPAC PM3 calculations, see: Schmidt & Polik (2007 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-66-0o574-scheme1.jpg

Experimental

Crystal data

  • C18H11BrN6
  • M r = 391.24
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-0o574-efi1.jpg
  • a = 12.0173 (5) Å
  • b = 17.4007 (7) Å
  • c = 7.4201 (4) Å
  • β = 91.004 (4)°
  • V = 1551.37 (12) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 2.66 mm−1
  • T = 200 K
  • 0.47 × 0.39 × 0.22 mm

Data collection

  • Oxford Diffraction Gemini diffractometer
  • Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007 [triangle]) T min = 0.494, T max = 1.000
  • 13458 measured reflections
  • 5032 independent reflections
  • 2606 reflections with I > 2σ(I)
  • R int = 0.050

Refinement

  • R[F 2 > 2σ(F 2)] = 0.036
  • wR(F 2) = 0.090
  • S = 1.14
  • 5032 reflections
  • 227 parameters
  • H-atom parameters constrained
  • Δρmax = 0.72 e Å−3
  • Δρmin = −0.71 e Å−3

Data collection: CrysAlis PRO (Oxford Diffraction, 2007 [triangle]); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I. DOI: 10.1107/S1600536810004368/bt5188sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810004368/bt5188Isup2.hkl

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

Acknowledgments

RJB acknowledges the NSF MRI program (grant No. CHE-0619278) for funds to purchase an X-ray diffractometer.

supplementary crystallographic information

Comment

Fused tetrazoles are known to be related to a variety of biological activities including anticancer relationships (Hiedo & Yasuo, 1960, 1961). Moreover their reductive ring cleavage ability may result in the formation of synthetically important 4-aminopyrimidine derivatives which are building blocks for the construction of ring systems such as pyrimidine and imidazole (Dave & Shukla, 1997). Furthermore, nucleophilic substitution with NaN3 results in either the formation of an azido group or tetrazole ring. An example of these reactions has been the synthesis of (7-Bromophenyl)-9-phenyl 7H-[1,2,3,4]tetrazolo[1,5-c]pyrrolo[3,2-e] pyrimidine by two different routes, either from 4-chloro-5-phenyl-(7-Bromophenyl)-7H-pyrrolo[2,3-d]pyrimidine or from 4-hydrazino-5-phenyl-(7-Bromophenyl)-7H-pyrrolo[2,3-d]pyrimidine (Dave & Shah, 1998) and then reduced to 4-amino-5-phenyl-(7-Bromophenyl)-7H-pyrrolo[2,3-d]pyrimidine. In view of the importance of these findings, we report the crystal structure of the title compound, C18H11BrN6, (I).

The title compond, (I), contains a pyrrole ring with successively fused pyrimidine and tetrazole rings, together with bromophenyl and benzene rings bonded at the N1 and C3 positions in a nearly planar fashion (Fig. 1). The nearly planar conformation of the pyrimidine ring is significant in that it is often found to be puckered which may be affected by the tetrazole and pyrrole ring fusion here. The least squares planes of the pyrimidine and tetrazole rings are oriented at the angles of 2.62 (15)° and 3.15 (15)° with the best plane of the pyrrole ring, respectively. The ortho-substituted 4-bromophenyl ring is twisted considerably, whereas the benzene ring at C3 is almost co-planar with the mean plane of the pyrrole ring, each having dihedral angles of 32.62 (15)° and 9.97 (16)°, respectively.

The crystal sructure is supported by weak C—H···Br and C—H···N intermolecular and weak C—H···N intramolecular interactions which link the molecules into chains along the [011] (Fig. 2, Table 1). An R22(8) graph-set motif (Bernstein et al., 1995) is established between the pyrrole, tetrazole and benzene rings resulting from these intermolecular interactions.

Crystal packing is also supported by two π-π stacking interactions (Fig. 3). One is between the centroids of two pyrrole rings [Cg2—Cg2; 3.7971 (17) Å; slippage = 1.318 Å; 1-x, 1-y, -z; Cg2 = N6/C3/C6/C5/C4]. The second is between the centroids of a pyrimidine (Cg3) and benzene (Cg4) ring [Cg3—Cg4: 3.5599 (16) Å; 1-x, 1-y, 1-z; Cg3 = N4/C1/C6/C3/N5/C2; Cg4 = C7—C12].

After a geometry optimized MOPAC PM3 computational calculation (Schmidt & Polik 2007) on (I), in vacuo, the angle between the mean planes of the pyrimidine, tetrazole and benzene groups become planar with the pyrrole ring in the local minimized structure. The dihedral angle between the ortho-substituted 4-bromophenyl ring and three planar tri-ring group becomes 42.28°. The separation of the H4A···H8A (2.111 Å) and H4A···H14A (2.301 Å) atoms between the pyrrole ring and the 4-bromophenyl and 9-phenyl rings before the calculations changed to 1.954 Å and 2.496 Å, respectively, after the calculation showing how the crystal packing effects significantly determine the twist of the 4-bromophenyl ring, in particular. In addition, the C3–C7 and N1–C13 bond lengths changed from 1.479 (3) Å and 1.430 (3) Å to 1.442 Å and 1.455 Å, respectively. It is clear that hydrogen bonding interactions and π-π stacking interactions significantly influence the twist angles for the molecule in this crystal.

Experimental

The synthesis of (I) was carried out by two separate routes. Route 1: To a mixture of NaN3 (0.011 m), NH4Cl (0.011 m) and DMSO (20 ml) was added 4-chloro-5-phenyl-(7-bromophenyl)-7H-pyrrolo[2,3-d]pyrimidine (0.001 m) in portions and stirred for 2 hrs at 363 K to give the title compound. Route 2: 4-hydrazino-5-phenyl-(7-bromophenyl)-7H-pyrrolo[2,3-d]pyrimidine (0.01 m) was diazotized with an aqueous solution of NaNO2 (20% w/v, 4.2 ml) and glacial acetic acid (40 ml) at 273-278 K under stirring conditions for 2 hrs to give the title compound. Colorless, plate-like crystals of (I) were grown by slow evaporation from 1,4-dioxane solution.

Refinement

All of the H atoms were placed in their calculated positions and then refined using the riding model with C—H = 0.95 Å, and with Uiso(H) = 1.18-1.21Ueq(C).

Figures

Fig. 1.
Molecular structure of C18H11BrN6, (I), showing the atom labeling scheme and 50% probability displacement ellipsoids.
Fig. 2.
The molecular packing for (I) viewed down the c axis. Dashed lines indicate weak C—H···N intermolecular hydrogen bond interactions which link the molecule into chains propagating along the [011].
Fig. 3.
The molecular packing of (I), showing π—π stacking interactions along the c axis and forming a chain of molecules along [1 1 0].

Crystal data

C18H11BrN6F(000) = 784
Mr = 391.24Dx = 1.675 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 4168 reflections
a = 12.0173 (5) Åθ = 4.8–32.4°
b = 17.4007 (7) ŵ = 2.66 mm1
c = 7.4201 (4) ÅT = 200 K
β = 91.004 (4)°Plate, colorless
V = 1551.37 (12) Å30.47 × 0.39 × 0.22 mm
Z = 4

Data collection

Oxford Diffraction Gemini diffractometer5032 independent reflections
Radiation source: fine-focus sealed tube2606 reflections with I > 2σ(I)
graphiteRint = 0.050
Detector resolution: 10.5081 pixels mm-1θmax = 32.5°, θmin = 4.8°
[var phi] and ω scansh = −16→18
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007)k = −25→26
Tmin = 0.494, Tmax = 1.000l = −11→11
13458 measured reflections

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.036H-atom parameters constrained
wR(F2) = 0.090w = 1/[σ2(Fo2) + (0.0295P)2] where P = (Fo2 + 2Fc2)/3
S = 1.14(Δ/σ)max < 0.001
5032 reflectionsΔρmax = 0.72 e Å3
227 parametersΔρmin = −0.71 e Å3
0 restraintsExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0033 (4)

Special details

Experimental. (CrysAlis RED; Oxford Diffraction, 2007)
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)

xyzUiso*/Ueq
Br−0.01667 (2)0.226033 (17)0.00063 (4)0.03758 (11)
N10.35315 (14)0.45391 (11)0.1749 (3)0.0245 (5)
N20.24838 (15)0.57000 (12)0.2186 (3)0.0300 (5)
N30.35441 (16)0.67017 (11)0.3359 (3)0.0292 (5)
N40.3685 (2)0.74165 (13)0.4080 (3)0.0406 (6)
N50.4737 (2)0.74487 (13)0.4525 (4)0.0432 (7)
N60.52928 (17)0.67915 (12)0.4136 (3)0.0359 (6)
C10.34572 (18)0.52985 (14)0.2224 (3)0.0235 (5)
C20.45169 (18)0.55548 (13)0.2756 (3)0.0219 (5)
C30.52682 (19)0.49222 (13)0.2569 (3)0.0230 (5)
C40.46260 (17)0.43241 (14)0.1955 (4)0.0245 (6)
H40.49020.38250.17030.029*
C50.2555 (2)0.63991 (16)0.2741 (4)0.0338 (7)
H50.19080.67130.27220.041*
C60.45368 (19)0.63216 (14)0.3404 (4)0.0263 (6)
C70.64817 (18)0.48691 (13)0.2913 (3)0.0225 (5)
C80.70547 (19)0.42147 (14)0.2367 (4)0.0277 (6)
H80.66590.38140.17690.033*
C90.8188 (2)0.41373 (15)0.2680 (4)0.0344 (7)
H90.85600.36870.22890.041*
C100.8778 (2)0.47079 (17)0.3551 (4)0.0351 (7)
H100.95560.46540.37670.042*
C110.82296 (19)0.53569 (16)0.4107 (4)0.0344 (7)
H110.86340.57520.47130.041*
C120.70894 (18)0.54451 (14)0.3794 (4)0.0283 (6)
H120.67250.58990.41810.034*
C130.26457 (18)0.40147 (14)0.1343 (3)0.0238 (6)
C140.16953 (19)0.42519 (15)0.0414 (4)0.0301 (6)
H140.16230.47710.00350.036*
C150.08552 (19)0.37323 (16)0.0039 (4)0.0308 (6)
H150.01950.3894−0.05740.037*
C160.09811 (19)0.29777 (15)0.0561 (4)0.0282 (6)
C170.19254 (19)0.27285 (15)0.1480 (4)0.0294 (6)
H170.20050.22050.18220.035*
C180.27530 (18)0.32577 (15)0.1893 (4)0.0293 (6)
H180.33970.31000.25560.035*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Br0.03221 (15)0.04452 (19)0.03605 (18)−0.01798 (12)0.00207 (11)−0.00499 (15)
N10.0192 (9)0.0240 (11)0.0302 (13)−0.0015 (8)−0.0006 (9)−0.0010 (10)
N20.0265 (11)0.0277 (12)0.0361 (15)0.0033 (9)0.0021 (10)−0.0018 (11)
N30.0332 (11)0.0193 (11)0.0354 (14)0.0034 (9)0.0050 (10)−0.0002 (10)
N40.0478 (14)0.0232 (13)0.0509 (17)0.0014 (10)0.0049 (12)−0.0054 (12)
N50.0527 (15)0.0195 (12)0.057 (2)−0.0027 (10)0.0016 (13)−0.0071 (12)
N60.0398 (12)0.0205 (12)0.0473 (16)−0.0030 (9)−0.0007 (11)−0.0038 (11)
C10.0236 (11)0.0220 (12)0.0250 (15)−0.0031 (10)0.0021 (10)−0.0002 (11)
C20.0249 (12)0.0186 (12)0.0222 (15)−0.0019 (9)0.0009 (10)0.0026 (11)
C30.0279 (13)0.0211 (13)0.0199 (13)−0.0029 (9)−0.0028 (10)0.0028 (11)
C40.0215 (11)0.0226 (13)0.0295 (16)0.0015 (9)0.0001 (10)−0.0001 (12)
C50.0281 (13)0.0334 (16)0.0399 (18)0.0067 (11)0.0029 (12)−0.0003 (14)
C60.0299 (13)0.0198 (13)0.0294 (16)−0.0005 (10)0.0044 (11)0.0061 (12)
C70.0206 (12)0.0232 (13)0.0237 (14)−0.0020 (9)−0.0001 (10)0.0048 (11)
C80.0274 (12)0.0210 (13)0.0343 (17)−0.0041 (10)−0.0050 (11)0.0037 (12)
C90.0342 (14)0.0269 (15)0.0418 (19)0.0075 (11)−0.0035 (13)0.0054 (13)
C100.0237 (13)0.0426 (16)0.0388 (19)0.0004 (12)−0.0085 (12)0.0022 (14)
C110.0291 (13)0.0352 (15)0.0387 (19)−0.0065 (12)−0.0077 (12)−0.0027 (14)
C120.0261 (12)0.0242 (14)0.0346 (17)−0.0022 (10)−0.0022 (11)−0.0011 (12)
C130.0243 (12)0.0256 (13)0.0216 (15)−0.0063 (10)0.0034 (10)−0.0033 (11)
C140.0275 (12)0.0294 (14)0.0334 (17)−0.0039 (10)0.0003 (12)0.0052 (13)
C150.0251 (13)0.0369 (16)0.0304 (16)−0.0043 (11)−0.0025 (11)0.0022 (13)
C160.0255 (12)0.0331 (15)0.0263 (16)−0.0093 (10)0.0075 (11)−0.0060 (12)
C170.0291 (13)0.0252 (13)0.0341 (16)−0.0027 (11)0.0036 (11)0.0019 (13)
C180.0213 (12)0.0313 (15)0.0352 (17)−0.0008 (10)−0.0010 (11)0.0036 (13)

Geometric parameters (Å, °)

Br—C161.900 (2)C7—C121.396 (3)
N1—C11.371 (3)C8—C91.383 (3)
N1—C41.373 (3)C8—H80.9500
N1—C131.430 (3)C9—C101.375 (4)
N2—C51.287 (3)C9—H90.9500
N2—C11.362 (3)C10—C111.374 (4)
N3—N41.363 (3)C10—H100.9500
N3—C61.364 (3)C11—C121.394 (3)
N3—C51.371 (3)C11—H110.9500
N4—N51.301 (3)C12—H120.9500
N5—N61.358 (3)C13—C181.384 (3)
N6—C61.331 (3)C13—C141.387 (3)
C1—C21.400 (3)C14—C151.380 (3)
C2—C61.418 (3)C14—H140.9500
C2—C31.432 (3)C15—C161.377 (4)
C3—C41.369 (3)C15—H150.9500
C3—C71.479 (3)C16—C171.383 (3)
C4—H40.9500C17—C181.386 (3)
C5—H50.9500C17—H170.9500
C7—C81.394 (3)C18—H180.9500
C1—N1—C4107.48 (18)C9—C8—H8119.3
C1—N1—C13128.14 (18)C7—C8—H8119.3
C4—N1—C13123.9 (2)C10—C9—C8120.4 (2)
C5—N2—C1115.2 (2)C10—C9—H9119.8
N4—N3—C6109.3 (2)C8—C9—H9119.8
N4—N3—C5125.7 (2)C11—C10—C9119.2 (2)
C6—N3—C5125.1 (2)C11—C10—H10120.4
N5—N4—N3104.6 (2)C9—C10—H10120.4
N4—N5—N6112.9 (2)C10—C11—C12121.0 (2)
C6—N6—N5105.6 (2)C10—C11—H11119.5
N2—C1—N1123.28 (19)C12—C11—H11119.5
N2—C1—C2128.2 (2)C11—C12—C7120.2 (2)
N1—C1—C2108.47 (19)C11—C12—H12119.9
C1—C2—C6113.9 (2)C7—C12—H12119.9
C1—C2—C3107.4 (2)C18—C13—C14120.1 (2)
C6—C2—C3138.5 (2)C18—C13—N1118.7 (2)
C4—C3—C2105.3 (2)C14—C13—N1121.2 (2)
C4—C3—C7123.9 (2)C15—C14—C13119.9 (2)
C2—C3—C7130.7 (2)C15—C14—H14120.1
C3—C4—N1111.3 (2)C13—C14—H14120.1
C3—C4—H4124.3C14—C15—C16119.5 (2)
N1—C4—H4124.3C14—C15—H15120.3
N2—C5—N3121.5 (2)C16—C15—H15120.3
N2—C5—H5119.2C15—C16—C17121.5 (2)
N3—C5—H5119.2C15—C16—Br119.33 (19)
N6—C6—N3107.6 (2)C17—C16—Br119.1 (2)
N6—C6—C2136.3 (2)C16—C17—C18118.7 (2)
N3—C6—C2116.0 (2)C16—C17—H17120.7
C8—C7—C12117.7 (2)C18—C17—H17120.7
C8—C7—C3119.4 (2)C17—C18—C13120.3 (2)
C12—C7—C3122.8 (2)C17—C18—H18119.9
C9—C8—C7121.4 (2)C13—C18—H18119.9
C6—N3—N4—N50.2 (3)C1—C2—C6—N6175.2 (3)
C5—N3—N4—N5178.1 (3)C3—C2—C6—N60.1 (6)
N3—N4—N5—N6−0.1 (3)C1—C2—C6—N3−2.1 (3)
N4—N5—N6—C6−0.1 (3)C3—C2—C6—N3−177.2 (3)
C5—N2—C1—N1177.5 (2)C4—C3—C7—C89.1 (4)
C5—N2—C1—C2−1.3 (4)C2—C3—C7—C8−170.4 (3)
C4—N1—C1—N2−179.8 (2)C4—C3—C7—C12−169.9 (3)
C13—N1—C1—N2−7.7 (4)C2—C3—C7—C1210.6 (4)
C4—N1—C1—C2−0.8 (3)C12—C7—C8—C9−0.2 (4)
C13—N1—C1—C2171.3 (2)C3—C7—C8—C9−179.3 (2)
N2—C1—C2—C63.1 (4)C7—C8—C9—C100.3 (4)
N1—C1—C2—C6−175.8 (2)C8—C9—C10—C11−0.1 (4)
N2—C1—C2—C3179.7 (2)C9—C10—C11—C12−0.2 (4)
N1—C1—C2—C30.8 (3)C10—C11—C12—C70.3 (4)
C1—C2—C3—C4−0.5 (3)C8—C7—C12—C11−0.1 (4)
C6—C2—C3—C4174.9 (3)C3—C7—C12—C11178.9 (2)
C1—C2—C3—C7179.1 (2)C1—N1—C13—C18−143.0 (3)
C6—C2—C3—C7−5.6 (5)C4—N1—C13—C1827.9 (4)
C2—C3—C4—N10.0 (3)C1—N1—C13—C1437.2 (4)
C7—C3—C4—N1−179.6 (2)C4—N1—C13—C14−151.9 (2)
C1—N1—C4—C30.5 (3)C18—C13—C14—C150.1 (4)
C13—N1—C4—C3−172.0 (2)N1—C13—C14—C15179.9 (2)
C1—N2—C5—N3−1.4 (4)C13—C14—C15—C16−1.4 (4)
N4—N3—C5—N2−175.5 (3)C14—C15—C16—C171.0 (4)
C6—N3—C5—N22.1 (4)C14—C15—C16—Br−178.9 (2)
N5—N6—C6—N30.2 (3)C15—C16—C17—C180.7 (4)
N5—N6—C6—C2−177.2 (3)Br—C16—C17—C18−179.4 (2)
N4—N3—C6—N6−0.3 (3)C16—C17—C18—C13−2.0 (4)
C5—N3—C6—N6−178.2 (2)C14—C13—C18—C171.6 (4)
N4—N3—C6—C2177.8 (2)N1—C13—C18—C17−178.2 (2)
C5—N3—C6—C2−0.1 (4)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
C8—H8···N4i0.952.543.421 (3)154
C4—H4···N5i0.952.603.532 (3)166
C5—H5···Brii0.952.873.667 (3)142

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

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT5188).

References

  • Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N. L. (1995). Angew. Chem. Int. Ed. Engl.34, 1555–1573.
  • Dave, C. G. & Shah, R. D. (1998). J. Heterocycl. Chem.35, 1295–1300.
  • Dave, C. G. & Shukla, M. C. (1997). J. Heterocycl. Chem.34, 1805–1808.
  • Hiedo, K. & Yasuo, M. (1960). Japan Patent 17,236.
  • Hiedo, K. & Yasuo, M. (1961). Chem. Abstr.55, 17664.
  • Oxford Diffraction (2007). CrysAlis PRO and CrysAlis RED Oxford Diffraction Ltd, Abingdon, England.
  • Schmidt, J. R. & Polik, W. F. (2007). WebMO Pro WebMO, LLC: Holland, MI, USA, available from http://www.webmo.net.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]

Articles from Acta Crystallographica Section E: Structure Reports Online are provided here courtesy of International Union of Crystallography