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Journal logoIUCrDATA
ISSN: 2414-3146
Volume 3| Part 6| June 2018| x180852
https://doi.org/10.1107/S2414314618008520

Hexa­cyclo­[6.5.1.01,5.05,12.07,11.09,13]tetra­decane-4,6,14-trione

Sambasivarao Kotha,a* Subba Rao Cheekatlaa and Rama Guntaa

aDepartment of Chemistry, Indian Institute of Technology - Bombay, Powai, Mumbai 400 076, India
*Correspondence e-mail: srk@chem.iitb.ac.in

Edited by M. Bolte, Goethe-Universität Frankfurt, Germany (Received 31 May 2018; accepted 9 June 2018; online 19 June 2018)

The structure of the title cage compound, C14H12O3, encompasses seven fused rings, viz. one four-membered, five five-membered and one six-membered. The four-membered ring is essentially planar, all five-membered rings adopt an envelope conformation and the six-membered ring adopts a boat conformation.

CCDC reference: 1842060

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3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

As a result of their rigid and strained architectures, polycyclic cage mol­ecules act as a useful scaffold for pharmaceutical applications (Liu et al., 2001[Liu, X., Nuwayhid, S., Christie, M. J., Kassiou, M. & Werling, L. L. (2001). Eur. J. Pharmacol. 422, 39-45.]; Wilkinson et al., 2014[Wilkinson, S. M., Gunosewoyo, H., Barron, M. L., Boucher, A., McDonnell, M., Turner, P., Morrison, D. E., Bennett, M. R., McGregor, I. S., Rendina, L. M. & Kassiou, M. (2014). ACS Chem. Neurosci. 5, 335-339.]), medicinal chemistry (Wanka et al., 2013[Wanka, L., Iqbal, K. & Schreiner, P. R. (2013). Chem. Rev. 113, 3516-3604.]; Liu et al., 2011[Liu, J., Obando, D., Liao, V., Lifa, T. & Codd, R. (2011). Eur. J. Med. Chem. 46, 1949-1963.]) and energetic materials (Wu et al., 2015[Wu, Q., Tan, L., Hang, Z., Wang, J., Zhang, Z. & Zhu, W. (2015). RSC Adv. 5, 93607-93614.]; Lal et al., 2014[Lal, S., Rajkumar, S., Tare, A., Reshmi, S., Chowdhury, A. & Namboothiri, I. N. N. (2014). Chem. Asian J. 9, 3533-3541.]). Some of the oxa-cage systems play an important role in mol­ecular recognition and inclusion phenomena (Marchand et al., 1998[Marchand, A. P., McKim, S. A. & Kumar, K. A. (1998). Tetrahedron, 54, 13421-13426.]). Cage hydro­carbons are useful as core frameworks for photonic/electronic materials (Giacalone & Martín, 2006[Giacalone, F. & Martín, N. (2006). Chem. Rev. 106, 5136-5190.]; Lebedeva et al., 2015[Lebedeva, M. A., Chamberlain, T. W. & Khlobystov, A. N. (2015). Chem. Rev. 115, 11301-11351.]) and ligands for organocatalysis (Biegasiewicz et al., 2012[Biegasiewicz, K. F., Ingalsbe, M. L., St , Denis, J. D., Gleason, J. L., Ho, J., Coote, M. L., Savage, G. P. & Priefer, R. (2012). Beilstein J. Org. Chem. 8, 1814-1818.]).

In view of our research inter­est in designing various new cage compounds, herein we report the structure and synthesis of the title compound (Fig. 1[link]). The title compound (II) was synthesized (Fig. 2[link]) from inexpensive and commercially available starting materials such as 2,5-dimeth­oxy benzaldehyde using the Diels–Alder reaction as a key step (Kotha et al., 2017[Kotha, S., Cheekatla, S. R. & Mandal, B. (2017). Eur. J. Org. Chem. pp. 4277-4282.]).

[Figure 1]
Figure 1
The mol­ecular structure of the title compound (II), with displacement ellipsoids drawn at the 50% probability level.
[Figure 2]
Figure 2
[2 + 2] photo­cyclo­addition of Diels–Alder adduct (I).

The mol­ecular structure of (II) is built up of seven rings: one four-membered, five five-membered and one six-membered rings are fused to a caged carbon framework. The four-membered ring is essentially planar. All five-membered rings adopt an envelope conformation, whereas the six-membered ring is in a boat conformation.

Synthesis and crystallization

The title cage compound can be prepared via a Diels–Alder reaction of cyclo­penta­diene with 2,3-di­hydro-1H-indene-1,4,7-trione followed by [2 + 2] photo­cyclo­addition. To begin with, Diels–Alder adduct (I) (100 mg, 0.43 mmol) was dissolved in dry ethyl acetate (300 ml) and irradiated in a Pyrex immersion well by using 125 W medium pressure UV mercury vapour lamp for 1 h under nitro­gen at room temperature. After completion of the reaction (TLC monitoring), the solvent was evaporated under reduced pressure and the crude reaction mixture was purified by silica-gel column chromatography using 40% ethyl acetate in petroleum ether as an eluent to furnish (II) as a colourless crystalline solid (92 mg, 94%). Recrystallization of a [2 + 2] photo­cyclo­adduct from a 1:4 mixture of di­chloro­methane–hexane solvent system delivered ortho­rhom­bic crystals of hexa­cyclic trione (II), m.p. 452–454 K (the melting point was recorded on a veego VMP–CMP melting point apparatus and is uncorrected). IR (neat, cm−1) 2976, 1757, 1740, 1434, 1266, 1139. 1H NMR (500 MHz, CDCl3, p.p.m.): 3.19 (t, J = 6.2 Hz, 1H), 3.05–3.02 (m, 3H), 2.80–2.74 (m, 2H), 2.69–2.60 (m, 1H), 2.53–2.40 (m, 2H), 2.08 (d, J = 11.5 Hz, 1H), 1.93 (d, J = 11.4 Hz, 1H), 1.89–1.84 (m, 1H). 13C NMR (125 MHz, CDCl3, p.p.m.): 210.7, 209.3, 205.2, 60.0, 56.6, 56.0, 54.7, 43.9, 43.6, 43.3, 42.8, 40.0, 39.9, 20.4; HRMS (ESI, Q-TOF) m/z calculated for C14H13O3 [M + H]+ 229.0859; found: 229.0855.

Refinement

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

Table 1
Experimental details

Crystal data
Chemical formula C14H12O3
Mr 228.24
Crystal system, space group Orthorhombic, P212121
Temperature (K) 150
a, b, c (Å) 7.4539 (5), 7.8553 (5), 17.2286 (10)
V (Å3) 1008.78 (11)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.11
Crystal size (mm) 0.21 × 0.18 × 0.03
 
Data collection
Diffractometer Manufacturer? Model?
Absorption correction Multi-scan (CrysAlis PRO; Rigaku OD, 2015[Rigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.])
Tmin, Tmax 0.874, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections 5609, 1769, 1553
Rint 0.059
(sin θ/λ)max (Å−1) 0.595
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.097, 1.07
No. of reflections 1769
No. of parameters 154
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.27, −0.26
Absolute structure Flack x determined using 530 quotients [(I+)−(I−)]/[(I+)+(I−)] (Parsons et al., 2013[Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249-259.])
Absolute structure parameter −0.4 (10)
Computer programs: CrysAlis PRO (Rigaku OD, 2015[Rigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]), SUPERFLIP (Palatinus & Chapuis, 2007[Palatinus, L. & Chapuis, G. (2007). J. Appl. Cryst. 40, 786-790.]; Palatinus & van der Lee, 2008[Palatinus, L. & van der Lee, A. (2008). J. Appl. Cryst. 41, 975-984.]; Palatinus et al., 2012[Palatinus, L., Prathapa, S. J. & van Smaalen, S. (2012). J. Appl. Cryst. 45, 575-580.]), SHELXL2018 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]) and OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]).

Structural data

CCDC reference: 1842060

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314618008520/bt4070sup1.cif

Supporting information file. DOI: https://doi.org/10.1107/S2414314618008520/bt4070Isup2.cml

checkCIF report


Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2015); cell refinement: CrysAlis PRO (Rigaku OD, 2015); data reduction: CrysAlis PRO (Rigaku OD, 2015); program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007; Palatinus & van der Lee, 2008; Palatinus et al., 2012); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Hexacyclo[6.5.1.01,5.05,12.07,11.09,13]tetradecane-4,6,14-trione top
Crystal data top
C14H12O3Dx = 1.503 Mg m−3
Mr = 228.24Melting point = 452–454 K
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
a = 7.4539 (5) ÅCell parameters from 3418 reflections
b = 7.8553 (5) Åθ = 2.3–30.9°
c = 17.2286 (10) ŵ = 0.11 mm−1
V = 1008.78 (11) Å3T = 150 K
Z = 4Plate, colourless
F(000) = 4800.21 × 0.18 × 0.03 mm
Data collection top
Rigaku Saturn724+ CCD
diffractometer		1769 independent reflections
Radiation source: fine-focus sealed X-ray tube, Enhance (Mo) X-ray Source1553 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.059
Detector resolution: 28.5714 pixels mm-1θmax = 25.0°, θmin = 2.4°
ω scansh = −8→6
Absorption correction: multi-scan
(CrysAlis PRO; Rigaku OD, 2015)		k = −9→9
Tmin = 0.874, Tmax = 1.000l = −20→20
5609 measured reflections
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.042 w = 1/[σ2(Fo2) + (0.0411P)2 + 0.1833P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.097(Δ/σ)max < 0.001
S = 1.07Δρmax = 0.27 e Å−3
1769 reflectionsΔρmin = −0.25 e Å−3
154 parametersAbsolute structure: Flack x determined using 530 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
0 restraintsAbsolute structure parameter: −0.4 (10)
Primary atom site location: iterative
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. All H atoms were placed in geometrically calculated positions and refined using a riding model with C–H distances of 1.00 Å for all H atoms bound to tertiary C(sp3) atoms and 0.99 Å for H atoms bound to secondary C(sp3) atoms. Isotropic displacement parameters for H atoms were calculated as Uiso(H) = 1.2Ueq(C). Due to the absence of anomalous scatterers, the absolute configuration could not be determined and was arbitrarily set.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O1−0.4454 (3)−0.5002 (3)−0.44952 (13)0.0323 (6)
O2−0.7382 (3)−0.2091 (3)−0.31876 (12)0.0283 (6)
O3−0.7593 (4)−0.5952 (3)−0.57320 (12)0.0386 (7)
C1−0.7649 (5)−0.7940 (4)−0.25367 (17)0.0236 (7)
H1A−0.678028−0.808534−0.2107230.028*
H1B−0.857452−0.884250−0.2513880.028*
C2−0.8456 (4)−0.6158 (4)−0.25598 (17)0.0213 (7)
H2−0.917858−0.582697−0.2094530.026*
C3−0.6831 (4)−0.5005 (4)−0.27393 (17)0.0212 (7)
H3−0.619466−0.458066−0.2266180.025*
C4−0.5625 (4)−0.6183 (4)−0.32811 (17)0.0201 (7)
H4−0.438219−0.636161−0.3078610.024*
C5−0.6744 (4)−0.7835 (4)−0.33247 (17)0.0213 (7)
H5−0.607082−0.887681−0.3487890.026*
C6−0.8299 (4)−0.7293 (4)−0.38685 (18)0.0203 (7)
H6−0.891741−0.821255−0.4167500.024*
C7−0.9485 (4)−0.6135 (4)−0.33487 (17)0.0189 (7)
H7−1.080298−0.637233−0.3336500.023*
C8−0.8843 (4)−0.4520 (4)−0.38033 (17)0.0201 (7)
C9−0.7637 (4)−0.5706 (4)−0.43341 (17)0.0205 (7)
C10−0.5679 (4)−0.5535 (4)−0.41111 (17)0.0208 (7)
C11−0.7643 (4)−0.3607 (4)−0.32306 (17)0.0211 (7)
C12−1.0053 (4)−0.3498 (4)−0.43411 (18)0.0254 (8)
H12A−0.956944−0.233685−0.4419200.030*
H12B−1.127812−0.340844−0.4122900.030*
C13−1.0076 (5)−0.4483 (5)−0.51065 (19)0.0334 (9)
H13A−1.109883−0.528665−0.5118040.040*
H13B−1.019144−0.368952−0.5550290.040*
C14−0.8314 (4)−0.5442 (4)−0.51511 (18)0.0247 (7)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0259 (13)0.0392 (15)0.0317 (14)−0.0016 (11)0.0053 (10)0.0096 (11)
O20.0378 (13)0.0185 (12)0.0285 (12)−0.0033 (11)−0.0014 (11)−0.0020 (10)
O30.0414 (14)0.0544 (16)0.0201 (12)0.0079 (14)0.0019 (12)−0.0031 (12)
C10.0246 (17)0.0219 (16)0.0243 (17)−0.0021 (15)0.0004 (14)0.0028 (14)
C20.0229 (16)0.0238 (16)0.0173 (16)0.0012 (16)0.0031 (13)−0.0018 (14)
C30.0246 (16)0.0227 (17)0.0163 (15)−0.0015 (15)−0.0035 (13)−0.0007 (14)
C40.0158 (15)0.0242 (17)0.0202 (16)0.0019 (14)−0.0023 (12)0.0021 (14)
C50.0240 (16)0.0174 (15)0.0224 (18)0.0025 (15)−0.0013 (14)0.0008 (13)
C60.0219 (16)0.0191 (15)0.0198 (17)−0.0015 (15)−0.0026 (14)−0.0009 (13)
C70.0169 (15)0.0194 (16)0.0203 (16)−0.0015 (13)0.0004 (13)−0.0013 (13)
C80.0195 (15)0.0219 (16)0.0188 (16)−0.0019 (14)−0.0027 (12)0.0002 (14)
C90.0229 (15)0.0219 (16)0.0168 (14)0.0005 (14)0.0010 (14)0.0002 (13)
C100.0199 (17)0.0176 (16)0.0249 (18)0.0019 (14)0.0042 (14)0.0004 (14)
C110.0252 (16)0.0189 (17)0.0193 (15)0.0013 (15)0.0060 (14)−0.0031 (13)
C120.0265 (17)0.0277 (17)0.0219 (16)0.0061 (16)−0.0012 (14)0.0011 (15)
C130.034 (2)0.043 (2)0.0230 (19)0.0080 (18)−0.0077 (15)−0.0020 (17)
C140.0284 (16)0.0279 (17)0.0177 (17)−0.0014 (16)−0.0006 (14)0.0009 (15)
Geometric parameters (Å, º) top
O1—C101.203 (4)C5—C61.550 (4)
O2—C111.209 (4)C6—H61.0000
O3—C141.204 (4)C6—C71.553 (4)
C1—H1A0.9900C6—C91.562 (4)
C1—H1B0.9900C7—H71.0000
C1—C21.524 (4)C7—C81.566 (4)
C1—C51.518 (4)C8—C91.585 (4)
C2—H21.0000C8—C111.513 (4)
C2—C31.544 (4)C8—C121.522 (4)
C2—C71.561 (4)C9—C101.516 (4)
C3—H31.0000C9—C141.509 (4)
C3—C41.592 (4)C12—H12A0.9900
C3—C111.513 (4)C12—H12B0.9900
C4—H41.0000C12—C131.529 (4)
C4—C51.544 (4)C13—H13A0.9900
C4—C101.518 (4)C13—H13B0.9900
C5—H51.0000C13—C141.517 (5)
H1A—C1—H1B110.1C6—C7—C2102.4 (2)
C2—C1—H1A112.6C6—C7—H7117.5
C2—C1—H1B112.6C6—C7—C890.7 (2)
C5—C1—H1A112.6C8—C7—H7117.5
C5—C1—H1B112.6C7—C8—C989.2 (2)
C5—C1—C295.9 (2)C11—C8—C7103.8 (2)
C1—C2—H2115.5C11—C8—C9108.6 (2)
C1—C2—C3103.5 (2)C11—C8—C12119.9 (3)
C1—C2—C7103.2 (2)C12—C8—C7123.4 (3)
C3—C2—H2115.5C12—C8—C9107.1 (2)
C3—C2—C7101.8 (2)C6—C9—C889.7 (2)
C7—C2—H2115.5C10—C9—C6104.1 (2)
C2—C3—H3113.8C10—C9—C8110.4 (2)
C2—C3—C4102.6 (2)C14—C9—C6118.9 (3)
C4—C3—H3113.8C14—C9—C8105.5 (2)
C11—C3—C2102.9 (2)C14—C9—C10123.1 (3)
C11—C3—H3113.8O1—C10—C4128.0 (3)
C11—C3—C4108.6 (2)O1—C10—C9128.5 (3)
C3—C4—H4113.6C9—C10—C4103.5 (2)
C5—C4—C3102.3 (2)O2—C11—C3128.0 (3)
C5—C4—H4113.6O2—C11—C8127.0 (3)
C10—C4—C3110.0 (2)C3—C11—C8104.9 (2)
C10—C4—H4113.6C8—C12—H12A110.7
C10—C4—C5102.8 (2)C8—C12—H12B110.7
C1—C5—C4104.0 (2)C8—C12—C13105.4 (3)
C1—C5—H5115.5H12A—C12—H12B108.8
C1—C5—C6102.9 (2)C13—C12—H12A110.7
C4—C5—H5115.5C13—C12—H12B110.7
C4—C5—C6101.7 (2)C12—C13—H13A110.4
C6—C5—H5115.5C12—C13—H13B110.4
C5—C6—H6117.2H13A—C13—H13B108.6
C5—C6—C7103.8 (2)C14—C13—C12106.6 (3)
C5—C6—C9107.1 (2)C14—C13—H13A110.4
C7—C6—H6117.2C14—C13—H13B110.4
C7—C6—C990.5 (2)O3—C14—C9125.5 (3)
C9—C6—H6117.2O3—C14—C13126.4 (3)
C2—C7—H7117.5C9—C14—C13108.1 (3)
C2—C7—C8107.2 (2)
C1—C2—C3—C433.3 (3)C7—C2—C3—C4−73.5 (2)
C1—C2—C3—C11146.1 (2)C7—C2—C3—C1139.3 (3)
C1—C2—C7—C6−33.1 (3)C7—C6—C9—C80.1 (2)
C1—C2—C7—C8−127.7 (3)C7—C6—C9—C10111.1 (2)
C1—C5—C6—C733.4 (3)C7—C6—C9—C14−107.5 (3)
C1—C5—C6—C9128.3 (3)C7—C8—C9—C6−0.1 (2)
C2—C1—C5—C452.9 (3)C7—C8—C9—C10−105.1 (3)
C2—C1—C5—C6−52.8 (3)C7—C8—C9—C14119.8 (3)
C2—C3—C4—C5−0.3 (3)C7—C8—C11—O2−150.2 (3)
C2—C3—C4—C10108.4 (3)C7—C8—C11—C330.7 (3)
C2—C3—C11—O2136.2 (3)C7—C8—C12—C13−80.9 (4)
C2—C3—C11—C8−44.7 (3)C8—C9—C10—O1−116.4 (3)
C2—C7—C8—C9103.4 (2)C8—C9—C10—C463.1 (3)
C2—C7—C8—C11−5.6 (3)C8—C9—C14—O3169.8 (3)
C2—C7—C8—C12−146.5 (3)C8—C9—C14—C13−12.0 (3)
C3—C2—C7—C674.0 (3)C8—C12—C13—C14−27.4 (4)
C3—C2—C7—C8−20.6 (3)C9—C6—C7—C2−107.9 (2)
C3—C4—C5—C1−33.0 (3)C9—C6—C7—C8−0.1 (2)
C3—C4—C5—C673.6 (3)C9—C8—C11—O2115.9 (4)
C3—C4—C10—O1117.1 (3)C9—C8—C11—C3−63.2 (3)
C3—C4—C10—C9−62.4 (3)C9—C8—C12—C1319.8 (3)
C4—C3—C11—O2−115.5 (4)C10—C4—C5—C1−147.2 (2)
C4—C3—C11—C863.6 (3)C10—C4—C5—C6−40.5 (3)
C4—C5—C6—C7−74.1 (3)C10—C9—C14—O342.0 (5)
C4—C5—C6—C920.8 (3)C10—C9—C14—C13−139.8 (3)
C5—C1—C2—C3−52.9 (3)C11—C3—C4—C5−108.8 (3)
C5—C1—C2—C752.9 (3)C11—C3—C4—C10−0.1 (3)
C5—C4—C10—O1−134.5 (3)C11—C8—C9—C6104.2 (3)
C5—C4—C10—C946.0 (3)C11—C8—C9—C10−0.8 (3)
C5—C6—C7—C2−0.1 (3)C11—C8—C9—C14−135.9 (3)
C5—C6—C7—C8107.6 (2)C11—C8—C12—C13144.1 (3)
C5—C6—C9—C8−104.5 (2)C12—C8—C9—C6−125.0 (3)
C5—C6—C9—C106.5 (3)C12—C8—C9—C10130.0 (3)
C5—C6—C9—C14147.9 (3)C12—C8—C9—C14−5.0 (3)
C6—C7—C8—C90.1 (2)C12—C8—C11—O2−7.6 (5)
C6—C7—C8—C11−108.9 (2)C12—C8—C11—C3173.3 (3)
C6—C7—C8—C12110.2 (3)C12—C13—C14—O3−157.1 (3)
C6—C9—C10—O1148.6 (3)C12—C13—C14—C924.8 (4)
C6—C9—C10—C4−31.9 (3)C14—C9—C10—O19.3 (5)
C6—C9—C14—O3−91.8 (4)C14—C9—C10—C4−171.3 (3)
C6—C9—C14—C1386.4 (3)
 

Acknowledgements

We thank Mr Darshan Matre for his help in collecting the X-ray data.

Funding information

We thank the Defence Research and Development Organization (DRDO, No. ARDB/01/1041849/M/1), New Delhi for financial assistance. SK thanks the Department of Science and Technology (DST, No. SR/S2/JCB-33/2010) for the award of a J. C. Bose fellowship and Praj Industries for a Chair Professorship (Green Chemistry). SRC thanks the University Grants Commission (UGC), New Delhi for the award of a research fellowship and RG thanks Indian Institute of Technology (IIT) – Bombay, Mumbai for financial support as an Institute Research Associate (RA).

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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoIUCrDATA
ISSN: 2414-3146
Volume 3| Part 6| June 2018| x180852
https://doi.org/10.1107/S2414314618008520
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