organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

N-(2-Oxo-2H-chromen-3-yl)benzamide

aDepartment of Physics, Bhavan's Sheth R. A. College of Science, Ahmedabad, Gujarat 380 001, India, bDepartment of Chemistry, M. G. Science Institute, Navrangpura, Ahmedabad, Gujarat 380 009, India, and cDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
*Correspondence e-mail: edward.tiekink@gmail.com

(Received 2 March 2010; accepted 4 March 2010; online 6 March 2010)

The phenyl ring in title mol­ecule, C16H11NO3, forms a dihedral angle of 7.69 (6)° with the fused ring system. The observed conformation is stabilized by intra­molecular N—H⋯O and C—H⋯O inter­actions. In the crystal, supra­molecular chains are formed along the b axis which are mediated by ππ inter­actions [centroid–centroid distance = 3.614 (2) Å].

Related literature

For the biological activity of imidazoles, see: Yohjiro et al. (1990[Yohjiro, H., Hiasao, S., Nobuyuki, K., Takuo, W. & Kazukuki, T. (1990). US Patent No. 4 902 705.]). For the anti-inflammatory activity of the title compound, see: Maddi et al. (2007[Maddi, V., Mamledesai, S. N., Satyanarayana, D. & Swamy, S. (2007). Indian J. Pharm. Sci. 69, 847-849.]). Semi-empirical quantum chemical calculations were performed using MOPAC2009 Stewart (2009[Stewart, J. P. (2009). MOPAC2009. Stewart Computational Chemistry. Available from: http://OpenMOPAC.net.]).

[Scheme 1]

Experimental

Crystal data
  • C16H11NO3

  • Mr = 265.26

  • Monoclinic, P 21 /c

  • a = 12.519 (4) Å

  • b = 4.748 (3) Å

  • c = 21.167 (4) Å

  • β = 102.044 (3)°

  • V = 1230.5 (9) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.10 mm−1

  • T = 293 K

  • 0.40 × 0.22 × 0.15 mm

Data collection
  • Bruker SMART APEX CCD diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.945, Tmax = 0.995

  • 13295 measured reflections

  • 2827 independent reflections

  • 2029 reflections with I > 2σ(I)

  • Rint = 0.025

Refinement
  • R[F2 > 2σ(F2)] = 0.040

  • wR(F2) = 0.118

  • S = 1.11

  • 2827 reflections

  • 184 parameters

  • 1 restraint

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.18 e Å−3

  • Δρmin = −0.18 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H1n⋯O1 0.87 (1) 2.24 (2) 2.659 (2) 110 (1)
C8—H8⋯O3 0.93 2.24 2.822 (3) 120

Data collection: APEX2 (Bruker, 2004[Bruker (2004). APEX2, SAINT and XPREP. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: APEX2 and SAINT (Bruker, 2004[Bruker (2004). APEX2, SAINT and XPREP. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT and XPREP (Bruker, 2004[Bruker (2004). APEX2, SAINT and XPREP. Bruker AXS Inc., Madison, Wisconsin, USA.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: ORTEP-3 (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]) and DIAMOND (Brandenburg, 2006[Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). publCIF. In preparation.]).

Supporting information


Comment top

Oxazoles are very useful synthetic intermediates used for the generation of imidazoles that possess a wide spectrum of biological activities such as herbicidal, anti-bacterial, anti-fungal, etc. (Yohjiro et al., 1990). During attempts designed to synthesize oxazoles containing various substituents at different positions in the benzene ring, the title compound, (I), was obtained unexpectedly by the formation of a chromen derivative instead of the anticipated oxazole. Compound (I) is a known species and has been shown to be pharmaceutically important as it possesses anti-inflammatory activity (Maddi et al., 2007).

There is a twist in the molecule of (I), Fig. 1, so that the pendent benzene ring is not co-planar with the rest of the molecule. This is seen in the value of the O3–C10–C11–C12 torsion angle of -166.43 (15) °, and in the dihedral formed between the fused ring system and benzene ring of 7.69 (6) °. The overall conformation of the molecule is stabilised by intramolecular N–H···O and C–H···O interactions, Table 1, which close S(5) and S(6) hydrogen bond ring motifs, respectively. The most prominent feature of the crystal packing is the formation of supramolecular chains along the b axis mediated by ππ interactions between the ring centroids of the (O2,C1,C2,C7—C9) and (C2—C7)i rings of 3.614 (2) Å of translationally related molecules; symmetry operation i: x, 1+y, z.

Semi-empirical Quantum Chemical Calculations were performed on experimental structure using MOPAC2009 program (Stewart, 2009) to optimize the molecule with the Austin Model 1 (AM1) approximation, together with the restricted Hartree-Fock closed-shell wavefunction. Minimisations were terminated at an r.m.s. gradient of less than 1.0 kJ mol-1 Å-1. These calculations gave a heat of formation = -213.437 kJ for (I). The ionization potential, dipole moment and self consistency field (SCF) factor were calculated as 9.033 eV, 1.798 Debye and 73, respectively.

Related literature top

For the biological activity of imidazoles, see: Yohjiro et al. (1990). For the anti-inflammatory activity of the title compound, see: Maddi et al. (2007). Semi-empirical quantum chemical calculations were performed using MOPAC2009 Stewart (2009).

Experimental top

A mixture of orthohydrothoxy benzaldehyde (0.25 mol), benzoyl amino acetic acid (0.25 mol), acetyl acetate (0.30 mol), and anhydrous sodium acetate (0.25 mol) were taken in a 500 ml round bottom flask and heated on an electric hot plate with constant stirring. After complete liquefaction, the flask was transferred to a sand bath and further heated for 2 h. Ethanol (100 ml) was added slowly to the flask and the mixture was allowed to stand overnight. The crystalline product obtained was filtered with ice-cold alcohol and then with boiling water. The crude product was crystallised from ethanol (95%) to obtain the final product (75 % yield, m.pt. 432 K). The colorless crystals were obtained by slow evaporation from an ethanol solution.

Refinement top

The C-bound H atoms were geometrically placed (C–H = 0.93 Å) and refined as riding with Uiso(H) = 1.2Ueq(parent atom). The position of the N–H atom was refined with Uiso(H) = 1.2Ueq(N).

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 and SAINT (Bruker, 2004); data reduction: SAINT and XPREP (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 35% probability level.
[Figure 2] Fig. 2. A supramolecular chain aligned along the b axis in (I), mediated by ππ interactions (purple dashed lines). Colour code: O, red; N, blue; C, grey; and H, green.
N-(2-Oxo-2H-chromen-3-yl)benzamide top
Crystal data top
C16H11NO3F(000) = 552
Mr = 265.26Dx = 1.432 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 3699 reflections
a = 12.519 (4) Åθ = 2.3–29.6°
b = 4.748 (3) ŵ = 0.10 mm1
c = 21.167 (4) ÅT = 293 K
β = 102.044 (3)°Block, colourless
V = 1230.5 (9) Å30.40 × 0.22 × 0.15 mm
Z = 4
Data collection top
Bruker SMART APEX CCD
diffractometer
2827 independent reflections
Radiation source: fine-focus sealed tube2029 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.025
ω and ϕ scansθmax = 27.5°, θmin = 1.7°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 1615
Tmin = 0.945, Tmax = 0.995k = 65
13295 measured reflectionsl = 2727
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.040Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.118H atoms treated by a mixture of independent and constrained refinement
S = 1.11 w = 1/[σ2(Fo2) + (0.0491P)2 + 0.2124P]
where P = (Fo2 + 2Fc2)/3
2827 reflections(Δ/σ)max = 0.001
184 parametersΔρmax = 0.18 e Å3
1 restraintΔρmin = 0.18 e Å3
Crystal data top
C16H11NO3V = 1230.5 (9) Å3
Mr = 265.26Z = 4
Monoclinic, P21/cMo Kα radiation
a = 12.519 (4) ŵ = 0.10 mm1
b = 4.748 (3) ÅT = 293 K
c = 21.167 (4) Å0.40 × 0.22 × 0.15 mm
β = 102.044 (3)°
Data collection top
Bruker SMART APEX CCD
diffractometer
2827 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
2029 reflections with I > 2σ(I)
Tmin = 0.945, Tmax = 0.995Rint = 0.025
13295 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0401 restraint
wR(F2) = 0.118H atoms treated by a mixture of independent and constrained refinement
S = 1.11Δρmax = 0.18 e Å3
2827 reflectionsΔρmin = 0.18 e Å3
184 parameters
Special details top

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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) top
xyzUiso*/Ueq
O10.57658 (10)0.4385 (3)0.56046 (6)0.0705 (4)
O20.69047 (9)0.1338 (2)0.61603 (5)0.0526 (3)
O30.85472 (10)0.6200 (3)0.43753 (6)0.0667 (4)
N10.70508 (10)0.5787 (3)0.48003 (6)0.0443 (3)
H1N0.6366 (8)0.619 (4)0.4767 (8)0.053*
C10.66406 (13)0.3252 (3)0.56770 (7)0.0469 (4)
C20.78915 (12)0.0059 (3)0.62787 (7)0.0426 (3)
C30.80701 (14)0.1960 (3)0.67819 (7)0.0534 (4)
H30.75450.22550.70270.064*
C40.90379 (15)0.3405 (4)0.69126 (8)0.0555 (4)
H40.91740.46880.72520.067*
C50.98102 (14)0.2972 (4)0.65453 (8)0.0552 (4)
H51.04630.39740.66350.066*
C60.96208 (13)0.1070 (3)0.60475 (8)0.0509 (4)
H61.01480.07930.58020.061*
C70.86511 (12)0.0452 (3)0.59038 (7)0.0414 (3)
C80.84018 (12)0.2473 (3)0.53927 (7)0.0440 (4)
H80.89090.28630.51400.053*
C90.74390 (12)0.3800 (3)0.52784 (6)0.0403 (3)
C100.76069 (13)0.6840 (3)0.43656 (7)0.0440 (4)
C110.70075 (12)0.8878 (3)0.38827 (7)0.0408 (3)
C120.60296 (13)1.0138 (3)0.39149 (7)0.0500 (4)
H120.56840.96850.42500.060*
C130.55600 (14)1.2065 (4)0.34538 (8)0.0579 (4)
H130.49011.29110.34810.069*
C140.60574 (15)1.2743 (4)0.29565 (8)0.0584 (5)
H140.57381.40470.26460.070*
C150.70244 (15)1.1497 (4)0.29178 (8)0.0590 (5)
H150.73601.19450.25780.071*
C160.75030 (14)0.9590 (3)0.33763 (7)0.0510 (4)
H160.81650.87650.33480.061*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0528 (7)0.0950 (10)0.0687 (8)0.0157 (7)0.0238 (6)0.0260 (7)
O20.0523 (7)0.0612 (7)0.0488 (6)0.0031 (5)0.0209 (5)0.0136 (5)
O30.0563 (7)0.0819 (9)0.0682 (8)0.0137 (6)0.0275 (6)0.0313 (7)
N10.0458 (7)0.0477 (7)0.0413 (7)0.0018 (6)0.0135 (6)0.0049 (5)
C10.0461 (9)0.0543 (9)0.0415 (8)0.0016 (7)0.0118 (6)0.0042 (7)
C20.0472 (8)0.0423 (8)0.0390 (7)0.0038 (6)0.0106 (6)0.0016 (6)
C30.0634 (10)0.0557 (9)0.0434 (8)0.0038 (8)0.0167 (7)0.0066 (7)
C40.0685 (11)0.0486 (9)0.0471 (9)0.0004 (8)0.0063 (8)0.0074 (7)
C50.0551 (10)0.0509 (9)0.0572 (10)0.0028 (8)0.0064 (8)0.0012 (8)
C60.0508 (9)0.0525 (9)0.0512 (9)0.0005 (7)0.0149 (7)0.0009 (7)
C70.0491 (8)0.0388 (7)0.0373 (7)0.0063 (6)0.0112 (6)0.0043 (6)
C80.0504 (9)0.0449 (8)0.0401 (7)0.0046 (7)0.0175 (6)0.0009 (6)
C90.0478 (8)0.0399 (7)0.0344 (7)0.0063 (6)0.0115 (6)0.0014 (6)
C100.0487 (9)0.0443 (8)0.0407 (8)0.0043 (7)0.0130 (6)0.0005 (6)
C110.0474 (8)0.0375 (7)0.0376 (7)0.0066 (6)0.0090 (6)0.0024 (6)
C120.0514 (9)0.0547 (9)0.0462 (8)0.0042 (8)0.0157 (7)0.0005 (7)
C130.0512 (10)0.0578 (10)0.0628 (10)0.0063 (8)0.0075 (8)0.0003 (8)
C140.0706 (12)0.0501 (9)0.0506 (9)0.0028 (8)0.0037 (8)0.0078 (8)
C150.0740 (12)0.0572 (10)0.0485 (9)0.0024 (9)0.0191 (8)0.0113 (8)
C160.0570 (9)0.0527 (9)0.0463 (8)0.0035 (8)0.0177 (7)0.0036 (7)
Geometric parameters (Å, º) top
O1—C11.2009 (19)C6—H60.9300
O2—C11.3567 (18)C7—C81.431 (2)
O2—C21.3783 (18)C8—C91.336 (2)
O3—C101.2118 (18)C8—H80.9300
N1—C101.3596 (19)C10—C111.492 (2)
N1—C91.3947 (19)C11—C121.377 (2)
N1—H1N0.867 (9)C11—C161.388 (2)
C1—C91.460 (2)C12—C131.377 (2)
C2—C31.378 (2)C12—H120.9300
C2—C71.381 (2)C13—C141.369 (3)
C3—C41.369 (2)C13—H130.9300
C3—H30.9300C14—C151.365 (2)
C4—C51.377 (2)C14—H140.9300
C4—H40.9300C15—C161.371 (2)
C5—C61.370 (2)C15—H150.9300
C5—H50.9300C16—H160.9300
C6—C71.391 (2)
C1—O2—C2121.85 (12)C9—C8—H8120.0
C10—N1—C9126.13 (13)C7—C8—H8120.0
C10—N1—H1N120.0 (11)C8—C9—N1127.93 (14)
C9—N1—H1N113.5 (11)C8—C9—C1120.79 (13)
O1—C1—O2117.93 (14)N1—C9—C1111.28 (13)
O1—C1—C9124.25 (14)O3—C10—N1121.95 (14)
O2—C1—C9117.81 (14)O3—C10—C11121.49 (13)
O2—C2—C3116.77 (14)N1—C10—C11116.55 (14)
O2—C2—C7120.63 (13)C12—C11—C16118.54 (14)
C3—C2—C7122.60 (15)C12—C11—C10124.99 (14)
C4—C3—C2118.57 (16)C16—C11—C10116.44 (14)
C4—C3—H3120.7C11—C12—C13120.41 (15)
C2—C3—H3120.7C11—C12—H12119.8
C3—C4—C5120.47 (15)C13—C12—H12119.8
C3—C4—H4119.8C14—C13—C12120.40 (17)
C5—C4—H4119.8C14—C13—H13119.8
C6—C5—C4120.23 (16)C12—C13—H13119.8
C6—C5—H5119.9C15—C14—C13119.71 (16)
C4—C5—H5119.9C15—C14—H14120.1
C5—C6—C7120.90 (15)C13—C14—H14120.1
C5—C6—H6119.5C14—C15—C16120.40 (16)
C7—C6—H6119.5C14—C15—H15119.8
C2—C7—C6117.21 (14)C16—C15—H15119.8
C2—C7—C8118.97 (14)C15—C16—C11120.53 (16)
C6—C7—C8123.82 (14)C15—C16—H16119.7
C9—C8—C7119.94 (14)C11—C16—H16119.7
C2—O2—C1—O1179.90 (14)C10—N1—C9—C1177.37 (14)
C2—O2—C1—C90.1 (2)O1—C1—C9—C8179.34 (16)
C1—O2—C2—C3179.91 (13)O2—C1—C9—C80.7 (2)
C1—O2—C2—C70.0 (2)O1—C1—C9—N10.5 (2)
O2—C2—C3—C4179.59 (14)O2—C1—C9—N1179.48 (12)
C7—C2—C3—C40.3 (2)C9—N1—C10—O33.4 (2)
C2—C3—C4—C50.4 (2)C9—N1—C10—C11177.89 (13)
C3—C4—C5—C60.5 (3)O3—C10—C11—C12166.43 (15)
C4—C5—C6—C70.0 (2)N1—C10—C11—C1212.3 (2)
O2—C2—C7—C6179.11 (13)O3—C10—C11—C1611.7 (2)
C3—C2—C7—C60.7 (2)N1—C10—C11—C16169.62 (14)
O2—C2—C7—C80.5 (2)C16—C11—C12—C130.2 (2)
C3—C2—C7—C8179.65 (14)C10—C11—C12—C13177.90 (14)
C5—C6—C7—C20.6 (2)C11—C12—C13—C140.3 (3)
C5—C6—C7—C8179.82 (14)C12—C13—C14—C150.1 (3)
C2—C7—C8—C91.0 (2)C13—C14—C15—C160.5 (3)
C6—C7—C8—C9178.53 (14)C14—C15—C16—C110.6 (3)
C7—C8—C9—N1179.05 (13)C12—C11—C16—C150.3 (2)
C7—C8—C9—C11.1 (2)C10—C11—C16—C15178.48 (14)
C10—N1—C9—C82.5 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1n···O10.87 (1)2.24 (2)2.659 (2)110 (1)
C8—H8···O30.932.242.822 (3)120

Experimental details

Crystal data
Chemical formulaC16H11NO3
Mr265.26
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)12.519 (4), 4.748 (3), 21.167 (4)
β (°) 102.044 (3)
V3)1230.5 (9)
Z4
Radiation typeMo Kα
µ (mm1)0.10
Crystal size (mm)0.40 × 0.22 × 0.15
Data collection
DiffractometerBruker SMART APEX CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.945, 0.995
No. of measured, independent and
observed [I > 2σ(I)] reflections
13295, 2827, 2029
Rint0.025
(sin θ/λ)max1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.040, 0.118, 1.11
No. of reflections2827
No. of parameters184
No. of restraints1
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.18, 0.18

Computer programs: APEX2 (Bruker, 2004), APEX2 and SAINT (Bruker, 2004), SAINT and XPREP (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 2006), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1n···O10.867 (11)2.236 (16)2.659 (2)110.0 (14)
C8—H8···O30.932.242.822 (3)120
 

Footnotes

Additional correspondence author, e-mail: mmjotani@rediffmail.com.

Acknowledgements

The authors are thankful to the Department of Science and Technology (DST), and the SAIF, IIT Madras, India, for the X-ray data collection. MMJ is grateful to the University Grant Commission (Western Regional Office), India, for Minor Research Project F (No. 47-254/07).

References

First citationBrandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.  Google Scholar
First citationBruker (2004). APEX2, SAINT and XPREP. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationFarrugia, L. J. (1997). J. Appl. Cryst. 30, 565.  CrossRef IUCr Journals Google Scholar
First citationMaddi, V., Mamledesai, S. N., Satyanarayana, D. & Swamy, S. (2007). Indian J. Pharm. Sci. 69, 847–849.  CrossRef CAS Google Scholar
First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationStewart, J. P. (2009). MOPAC2009. Stewart Computational Chemistry. Available from: http://OpenMOPAC.net.  Google Scholar
First citationWestrip, S. P. (2010). publCIF. In preparation.  Google Scholar
First citationYohjiro, H., Hiasao, S., Nobuyuki, K., Takuo, W. & Kazukuki, T. (1990). US Patent No. 4 902 705.  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.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds