organic compounds
(E)-3-(2-Chlorophenyl)-1-(2,4-dichlorophenyl)prop-2-en-1-one
aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, bDepartment of Chemistry, Faculty of Science, Prince of Songkla University, Hat-Yai, Songkhla 90112, Thailand, and cDepartment of Studies in Physics, Mangalore University, Mangalagangotri, Mangalore 574 199, India
*Correspondence e-mail: hkfun@usm.my
In the title chalcone derivative, C15H9Cl3O, the dihedral angle between the 2-chlorophenyl and 2,4-dichlorophenyl rings is 41.79 (14)°. Weak C—H⋯O and C—H⋯Cl intramolecular interactions involving the enone unit generate S(5) ring motifs. In the the molecules are arranged in a head-to-tail manner along the a axis. These chains are stacked along the b axis.
Related literature
For related literature on hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987). For related structures, see, for example: Fun, Chantrapromma et al. (2007); Fun, Patil et al. (2007); Patil, Chantrapromma et al. (2007; Patil, Fun et al. (2007). For background to the applications of substituted see, for example: Agrinskaya et al. (1999); Gu et al. (2008); Patil, Dharmaprakash et al. (2007).
Experimental
Crystal data
|
Refinement
|
|
Data collection: APEX2 (Bruker, 2005); cell APEX2; data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003).
Supporting information
10.1107/S160053680801413X/is2291sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S160053680801413X/is2291Isup2.hkl
The title compound was synthesized by the condensation of 2-chlorobenzaldehyde (0.01 mol) with 2,4-dichloroacetophenones (0.01 mol) in methanol (60 ml) in the presence of a catalytic amount of sodium hydroxide solution (5 ml, 30%). After stirring (4 h), the contents of the flask were poured into ice-cold water (500 ml) and left to stand for 6 h. The resulting crude solid was filtered and dried. Colorless block-shaped single crystals of the title compound suitable for X-ray
were recrystallized from acetone by slow evaporation of the solvent at room temperature.All H atoms were placed in calculated positions (C—H = 0.93 Å) and treated as riding, with Uiso(H) = 1.2Ueq(C). The highest residual electron density peak is located at 1.90 Å from C13 and the deepest hole is located at 0.93 Å from Cl2.
Data collection: APEX2 (Bruker, 2005); cell
APEX2 (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2003).C15H9Cl3O | F(000) = 1264 |
Mr = 311.57 | Dx = 1.584 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 2976 reflections |
a = 50.177 (2) Å | θ = 0.8–27.5° |
b = 3.8082 (2) Å | µ = 0.69 mm−1 |
c = 13.7297 (7) Å | T = 100 K |
β = 95.307 (3)° | Block, colorless |
V = 2612.3 (2) Å3 | 0.39 × 0.20 × 0.14 mm |
Z = 8 |
Bruker SMART APEX2 CCD area-detector diffractometer | 2976 independent reflections |
Radiation source: fine-focus sealed tube | 2374 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.054 |
Detector resolution: 8.33 pixels mm-1 | θmax = 27.5°, θmin = 0.8° |
ω scans | h = −64→64 |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | k = −4→4 |
Tmin = 0.775, Tmax = 0.911 | l = −17→17 |
13605 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.066 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.189 | H-atom parameters constrained |
S = 1.13 | w = 1/[σ2(Fo2) + (0.0626P)2 + 28.0963P] where P = (Fo2 + 2Fc2)/3 |
2976 reflections | (Δ/σ)max = 0.001 |
172 parameters | Δρmax = 0.52 e Å−3 |
0 restraints | Δρmin = −0.58 e Å−3 |
C15H9Cl3O | V = 2612.3 (2) Å3 |
Mr = 311.57 | Z = 8 |
Monoclinic, C2/c | Mo Kα radiation |
a = 50.177 (2) Å | µ = 0.69 mm−1 |
b = 3.8082 (2) Å | T = 100 K |
c = 13.7297 (7) Å | 0.39 × 0.20 × 0.14 mm |
β = 95.307 (3)° |
Bruker SMART APEX2 CCD area-detector diffractometer | 2976 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | 2374 reflections with I > 2σ(I) |
Tmin = 0.775, Tmax = 0.911 | Rint = 0.054 |
13605 measured reflections |
R[F2 > 2σ(F2)] = 0.066 | 0 restraints |
wR(F2) = 0.189 | H-atom parameters constrained |
S = 1.13 | w = 1/[σ2(Fo2) + (0.0626P)2 + 28.0963P] where P = (Fo2 + 2Fc2)/3 |
2976 reflections | Δρmax = 0.52 e Å−3 |
172 parameters | Δρmin = −0.58 e Å−3 |
Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. |
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. |
x | y | z | Uiso*/Ueq | ||
Cl1 | 0.24912 (2) | 0.3582 (3) | 0.13634 (9) | 0.0253 (3) | |
Cl2 | 0.32818 (2) | 0.9466 (3) | −0.04254 (9) | 0.0272 (3) | |
Cl3 | 0.46557 (2) | 0.9477 (4) | 0.12885 (9) | 0.0320 (3) | |
O1 | 0.37362 (7) | 0.9696 (11) | 0.2294 (3) | 0.0353 (9) | |
C1 | 0.32520 (9) | 0.5622 (13) | 0.2282 (4) | 0.0240 (10) | |
H1A | 0.3364 | 0.5366 | 0.2855 | 0.029* | |
C2 | 0.29887 (9) | 0.4535 (13) | 0.2272 (4) | 0.0247 (10) | |
H2A | 0.2924 | 0.3562 | 0.2825 | 0.030* | |
C3 | 0.28239 (8) | 0.4941 (13) | 0.1413 (4) | 0.0232 (10) | |
C4 | 0.29124 (9) | 0.6481 (12) | 0.0592 (3) | 0.0225 (10) | |
H4A | 0.2797 | 0.6825 | 0.0030 | 0.027* | |
C5 | 0.31790 (9) | 0.7503 (13) | 0.0626 (4) | 0.0237 (10) | |
C6 | 0.33539 (9) | 0.7072 (13) | 0.1473 (3) | 0.0226 (10) | |
C7 | 0.36458 (9) | 0.8125 (15) | 0.1559 (4) | 0.0292 (11) | |
C8 | 0.38100 (10) | 0.7060 (15) | 0.0778 (4) | 0.0312 (11) | |
H8A | 0.3740 | 0.5518 | 0.0295 | 0.037* | |
C9 | 0.40609 (9) | 0.8285 (15) | 0.0751 (4) | 0.0310 (11) | |
H9A | 0.4126 | 0.9814 | 0.1245 | 0.037* | |
C10 | 0.42374 (10) | 0.7390 (14) | 0.0006 (4) | 0.0298 (11) | |
C11 | 0.41423 (10) | 0.6012 (15) | −0.0914 (4) | 0.0346 (12) | |
H11A | 0.3960 | 0.5603 | −0.1046 | 0.042* | |
C12 | 0.43090 (11) | 0.5256 (15) | −0.1619 (4) | 0.0357 (12) | |
H12A | 0.4239 | 0.4393 | −0.2224 | 0.043* | |
C13 | 0.45816 (11) | 0.5780 (15) | −0.1430 (4) | 0.0357 (12) | |
H13A | 0.4695 | 0.5252 | −0.1907 | 0.043* | |
C14 | 0.46862 (9) | 0.7084 (14) | −0.0535 (4) | 0.0298 (11) | |
H14A | 0.4870 | 0.7433 | −0.0406 | 0.036* | |
C15 | 0.45143 (9) | 0.7860 (13) | 0.0163 (4) | 0.0263 (10) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl1 | 0.0192 (5) | 0.0235 (6) | 0.0333 (6) | −0.0020 (4) | 0.0024 (4) | 0.0004 (5) |
Cl2 | 0.0291 (6) | 0.0242 (6) | 0.0288 (6) | −0.0030 (5) | 0.0058 (4) | 0.0011 (5) |
Cl3 | 0.0250 (6) | 0.0343 (7) | 0.0363 (7) | −0.0035 (5) | 0.0016 (5) | 0.0009 (6) |
O1 | 0.0274 (17) | 0.042 (2) | 0.036 (2) | −0.0053 (16) | −0.0011 (14) | −0.0058 (18) |
C1 | 0.024 (2) | 0.021 (2) | 0.027 (2) | 0.0057 (18) | −0.0006 (17) | −0.004 (2) |
C2 | 0.024 (2) | 0.019 (2) | 0.032 (3) | 0.0036 (18) | 0.0049 (18) | 0.000 (2) |
C3 | 0.0156 (19) | 0.024 (2) | 0.031 (2) | −0.0004 (17) | 0.0051 (17) | −0.004 (2) |
C4 | 0.024 (2) | 0.017 (2) | 0.025 (2) | 0.0020 (17) | −0.0019 (17) | −0.0009 (19) |
C5 | 0.025 (2) | 0.018 (2) | 0.028 (2) | 0.0008 (18) | 0.0052 (18) | 0.000 (2) |
C6 | 0.021 (2) | 0.021 (2) | 0.026 (2) | 0.0021 (18) | 0.0032 (17) | 0.000 (2) |
C7 | 0.026 (2) | 0.032 (3) | 0.029 (3) | −0.001 (2) | 0.0028 (19) | 0.002 (2) |
C8 | 0.026 (2) | 0.032 (3) | 0.035 (3) | 0.001 (2) | 0.001 (2) | 0.000 (2) |
C9 | 0.027 (2) | 0.033 (3) | 0.033 (3) | 0.001 (2) | 0.002 (2) | 0.002 (2) |
C10 | 0.027 (2) | 0.028 (3) | 0.035 (3) | −0.001 (2) | 0.004 (2) | 0.008 (2) |
C11 | 0.032 (3) | 0.031 (3) | 0.041 (3) | −0.005 (2) | 0.000 (2) | 0.006 (2) |
C12 | 0.042 (3) | 0.026 (3) | 0.038 (3) | 0.000 (2) | −0.003 (2) | −0.001 (2) |
C13 | 0.034 (3) | 0.031 (3) | 0.043 (3) | 0.006 (2) | 0.007 (2) | −0.002 (3) |
C14 | 0.022 (2) | 0.028 (3) | 0.040 (3) | 0.002 (2) | 0.0045 (19) | 0.002 (2) |
C15 | 0.025 (2) | 0.019 (2) | 0.035 (3) | −0.0010 (19) | 0.0021 (19) | 0.006 (2) |
Cl1—C3 | 1.743 (4) | C8—C9 | 1.347 (7) |
Cl2—C5 | 1.746 (5) | C8—H8A | 0.9300 |
Cl3—C15 | 1.751 (5) | C9—C10 | 1.454 (7) |
O1—C7 | 1.224 (6) | C9—H9A | 0.9300 |
C1—C6 | 1.380 (7) | C10—C15 | 1.398 (6) |
C1—C2 | 1.383 (6) | C10—C11 | 1.410 (8) |
C1—H1A | 0.9300 | C11—C12 | 1.367 (8) |
C2—C3 | 1.385 (7) | C11—H11A | 0.9300 |
C2—H2A | 0.9300 | C12—C13 | 1.383 (7) |
C3—C4 | 1.380 (7) | C12—H12A | 0.9300 |
C4—C5 | 1.390 (6) | C13—C14 | 1.382 (8) |
C4—H4A | 0.9300 | C13—H13A | 0.9300 |
C5—C6 | 1.400 (6) | C14—C15 | 1.380 (7) |
C6—C7 | 1.512 (6) | C14—H14A | 0.9300 |
C7—C8 | 1.468 (7) | ||
C6—C1—C2 | 122.4 (4) | C7—C8—H8A | 119.6 |
C6—C1—H1A | 118.8 | C8—C9—C10 | 124.7 (5) |
C2—C1—H1A | 118.8 | C8—C9—H9A | 117.6 |
C1—C2—C3 | 118.0 (4) | C10—C9—H9A | 117.6 |
C1—C2—H2A | 121.0 | C15—C10—C11 | 115.8 (5) |
C3—C2—H2A | 121.0 | C15—C10—C9 | 121.5 (5) |
C4—C3—C2 | 122.1 (4) | C11—C10—C9 | 122.7 (5) |
C4—C3—Cl1 | 118.3 (4) | C12—C11—C10 | 122.3 (5) |
C2—C3—Cl1 | 119.6 (4) | C12—C11—H11A | 118.8 |
C3—C4—C5 | 118.2 (4) | C10—C11—H11A | 118.8 |
C3—C4—H4A | 120.9 | C11—C12—C13 | 119.7 (5) |
C5—C4—H4A | 120.9 | C11—C12—H12A | 120.2 |
C4—C5—C6 | 121.5 (4) | C13—C12—H12A | 120.2 |
C4—C5—Cl2 | 116.7 (4) | C14—C13—C12 | 120.5 (5) |
C6—C5—Cl2 | 121.8 (3) | C14—C13—H13A | 119.8 |
C1—C6—C5 | 117.7 (4) | C12—C13—H13A | 119.8 |
C1—C6—C7 | 118.2 (4) | C15—C14—C13 | 118.9 (5) |
C5—C6—C7 | 124.1 (4) | C15—C14—H14A | 120.5 |
O1—C7—C8 | 123.2 (4) | C13—C14—H14A | 120.5 |
O1—C7—C6 | 118.4 (4) | C14—C15—C10 | 122.8 (5) |
C8—C7—C6 | 118.4 (4) | C14—C15—Cl3 | 117.4 (4) |
C9—C8—C7 | 120.9 (5) | C10—C15—Cl3 | 119.8 (4) |
C9—C8—H8A | 119.6 | ||
C6—C1—C2—C3 | −0.1 (7) | O1—C7—C8—C9 | −11.5 (8) |
C1—C2—C3—C4 | −2.1 (7) | C6—C7—C8—C9 | 171.6 (5) |
C1—C2—C3—Cl1 | 179.6 (4) | C7—C8—C9—C10 | −179.7 (5) |
C2—C3—C4—C5 | 2.9 (7) | C8—C9—C10—C15 | −160.7 (5) |
Cl1—C3—C4—C5 | −178.8 (4) | C8—C9—C10—C11 | 19.5 (9) |
C3—C4—C5—C6 | −1.4 (7) | C15—C10—C11—C12 | −1.5 (8) |
C3—C4—C5—Cl2 | −179.6 (4) | C9—C10—C11—C12 | 178.4 (5) |
C2—C1—C6—C5 | 1.4 (7) | C10—C11—C12—C13 | 1.3 (9) |
C2—C1—C6—C7 | −179.1 (5) | C11—C12—C13—C14 | −0.4 (9) |
C4—C5—C6—C1 | −0.6 (7) | C12—C13—C14—C15 | −0.1 (8) |
Cl2—C5—C6—C1 | 177.4 (4) | C13—C14—C15—C10 | −0.1 (8) |
C4—C5—C6—C7 | 180.0 (5) | C13—C14—C15—Cl3 | 179.6 (4) |
Cl2—C5—C6—C7 | −2.0 (7) | C11—C10—C15—C14 | 0.9 (8) |
C1—C6—C7—O1 | −44.2 (7) | C9—C10—C15—C14 | −179.0 (5) |
C5—C6—C7—O1 | 135.2 (5) | C11—C10—C15—Cl3 | −178.8 (4) |
C1—C6—C7—C8 | 132.8 (5) | C9—C10—C15—Cl3 | 1.3 (7) |
C5—C6—C7—C8 | −47.8 (7) |
D—H···A | D—H | H···A | D···A | D—H···A |
C9—H9A···Cl3 | 0.93 | 2.66 | 3.042 (5) | 106 |
C9—H9A···O1 | 0.93 | 2.53 | 2.841 (6) | 100 |
Experimental details
Crystal data | |
Chemical formula | C15H9Cl3O |
Mr | 311.57 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 100 |
a, b, c (Å) | 50.177 (2), 3.8082 (2), 13.7297 (7) |
β (°) | 95.307 (3) |
V (Å3) | 2612.3 (2) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.69 |
Crystal size (mm) | 0.39 × 0.20 × 0.14 |
Data collection | |
Diffractometer | Bruker SMART APEX2 CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2005) |
Tmin, Tmax | 0.775, 0.911 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 13605, 2976, 2374 |
Rint | 0.054 |
(sin θ/λ)max (Å−1) | 0.650 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.066, 0.189, 1.13 |
No. of reflections | 2976 |
No. of parameters | 172 |
H-atom treatment | H-atom parameters constrained |
w = 1/[σ2(Fo2) + (0.0626P)2 + 28.0963P] where P = (Fo2 + 2Fc2)/3 | |
Δρmax, Δρmin (e Å−3) | 0.52, −0.58 |
Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2003).
D—H···A | D—H | H···A | D···A | D—H···A |
C9—H9A···Cl3 | 0.93 | 2.66 | 3.042 (5) | 106 |
C9—H9A···O1 | 0.93 | 2.53 | 2.841 (6) | 100 |
Footnotes
‡Additional correspondence author, e-mail: suchada.c@psu.ac.th.
Acknowledgements
This work is supported by the Department of Science and Technology (DST), Government of India, under grant No. SR/S2/LOP-17/2006. The authors also thank Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012.
References
Agrinskaya, N. V., Lukoshkin, V. A., Kudryavtsev, V. V., Nosova, G. I., Solovskaya, N. A. & Yakimanski, A. V. (1999). Phys. Solid State, 41, 1914–1917. Web of Science CrossRef CAS Google Scholar
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–S19. CrossRef Web of Science Google Scholar
Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573. CrossRef CAS Web of Science Google Scholar
Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Fun, H.-K., Chantrapromma, S., Patil, P. S. & Dharmaprakash, S. M. (2007). Acta Cryst. E63, o2724–o2725. Web of Science CSD CrossRef IUCr Journals Google Scholar
Fun, H.-K., Patil, P. S., Dharmaprakash, S. M. & Chantrapromma, S. (2007). Acta Cryst. E63, o561–o562. Web of Science CSD CrossRef IUCr Journals Google Scholar
Gu, B., Ji, W., Patil, P. S., Dharmaprakash, S. M. & Wang, H. T. (2008). Appl. Phys. Lett. 92, 091118–091120. Web of Science CrossRef Google Scholar
Patil, P. S., Chantrapromma, S., Fun, H.-K. & Dharmaprakash, S. M. (2007). Acta Cryst. E63, o1738–o1740. Web of Science CSD CrossRef IUCr Journals Google Scholar
Patil, P. S., Fun, H.-K., Chantrapromma, S. & Dharmaprakash, S. M. (2007). Acta Cryst. E63, o2497–o2498. Web of Science CSD CrossRef IUCr Journals Google Scholar
Patil, P. S., Dharmaprakash, S. M., Ramakrishna, K., Fun, H.-K., Sai Santosh Kumar, R. & Rao, D. N. (2007). J. Cryst. Growth, 303, 520–524. Web of Science CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13. Web of Science CrossRef CAS IUCr Journals Google Scholar
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.
Nonlinear optical properties of chalcone derivatives have been widely investigated recently (Agrinskaya et al., 1999; Fun, Chantrapromma et al., 2007; Fun, Patil et al., 2007; Patil, Dharmaprakash et al., 2007; Patil, Chantrapromma et al., 2007; Patil, Fun et al., 2007). These molecules show potential in optical-limiting applications due to their large excited-state absorption cross sections (Gu et al., 2008). In view of the importance of chalcones and the continuation of our non-linear optic materials research the title chalcone derivative, (I), was synthesized and its crystal structure is reported here.
In the structure of the title chalcone derivative (Fig. 1), the enone unit O1/C6–C8, the 2-chlorophenyl and 2,4-dichlorophenyl rings are individually planar, with the maximum deviations of 0.016 (6), -0.017 (6) and 0.022 (5) Å for atom C7, C11 and C2, respectively. The molecule is slightly twisted about the C6–C7 bond as indicated by the torsion angles C1–C6–C7–C8 = 132.8 (5)°, C6–C7–C8–C9 = 171.6 (5)°, C7–C8–C9–C10 = -179.7 (5)° and C8–C9–C10–C15 = -160.7 (5)°. The dihedral angles between the 2-chlorophenyl and 2,4-dichlorophenyl rings is 41.79 (14)°. The least-squares plane through the enone unit makes dihedral angles of 10.3 (3)° and 46.9 (2)° with the 2-chlorophenyl and 2,4-dichlorophenyl rings, respectively. The orientation of the prop-2-en-1-one unit can be indicated by the torsion angle O1–C7–C8–C9 = -11.5 (8)°. Bond lengths and angles in (I) are in normal ranges (Allen et al., 1987) and comparable to those in related structures (Fun, Chantrapromma et al., 2007; Fun, Patil et al., 2007; Patil, Dharmaprakash et al., 2007; Patil, Chantrapromma et al., 2007; Patil, Fun et al., 2007).
In the molecular structure, both weak C9—H9A···O1 and C9—H9A···Cl1 intramolecular interactions (Table 1) generate S(5) ring motifs (Bernstein et al., 1995). In the crystal structure (Fig. 2), the molecules are arranged in a head-to-tail manner along the a-axis. These chains are stacked along the b axis.