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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

2-Eth­­oxy-5-methylbis[1,2,4]triazolo[1,5-a:4′,3′-c]quinazoline

aDepartment of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia, and bDepartment of Chemistry, Institute of Pharmacy, University of Hamburg, Bundesstrasse 45, 20146, Hamburg, Germany
*Correspondence e-mail: abari@ksu.edu.sa

(Received 1 November 2011; accepted 7 December 2011; online 14 December 2011)

The title compound, C13H12N6O, is a functionalized ditriazoloquinazoline with substituted eth­oxy and methyl groups attached at the 2-position of each triazole spacer. The fused-ring system is essentially planar [r.m.s. deviation = 0.016 (2) Å]. In the crystal, a weak C—H⋯N hydrogen bond connects the mol­ecules into a chain along [101].

Related literature

For the biological activity of quinazoline derviatives, see: Alagarsamy et al. (2005[Alagarsamy, V., Giridhar, R. & Yadav, M. R. (2005). Bioorg. Med. Chem. Lett. 15, 1877-1880.], 2007[Alagarsamy, V., Solomon, V. R. & Murugan, M. (2007). Bioorg. Med. Chem. 15, 4009-4015.]). For our study of the chemical and pharmacological properties of triazolo quinazoline deriv­atives, see: Al-Salahi (2009[Al-Salahi, R. (2009). PhD dissertation, Hamburg University, Germany.]); Al-Salahi et al. (2010[Al-Salahi, R. & Geffken, D. (2010). Molecules, 15, 7016-7034.], 2011[Al-Salahi, R., Geffken, D. & Koellner, M. (2011). Chem. Pharm. Bull. 59, 730-733.]); Berezank et al. (2008a[Berezank, J. F., Chan, D., Geffken, D., Hanagan, M. A., Lepone, G. E., Pasteris, R. S. & Swan, T. (2008a). World patent WO 2008103357.],b[Berezank, J. F., Chan, D., Geffken, D., Hanagan, M. A., Lepone, G. E., Pasteris, R. S. & Swan, T. (2008b). Chem. Abstr. 1042828.]). For related structures, see: El-Tombary et al. (1999[El-Tombary, A. A., Ismail, K. A., Aboulwafa, O. M., Omar, A.-M., El-Azzouni, M. Z. & El-Mansoury, S. T. (1999). Farmaco, 54, 486-488.]).

[Scheme 1]

Experimental

Crystal data
  • C13H12N6O

  • Mr = 268.29

  • Monoclinic, P 21 /c

  • a = 7.4121 (11) Å

  • b = 19.240 (3) Å

  • c = 9.3096 (14) Å

  • β = 109.051 (2)°

  • V = 1254.9 (3) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.10 mm−1

  • T = 153 K

  • 0.43 × 0.21 × 0.05 mm

Data collection
  • Bruker SMART APEX CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 1998[Bruker (1998). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.959, Tmax = 0.995

  • 2851 measured reflections

  • 2851 independent reflections

  • 1817 reflections with I > 2σ(I)

  • Rint = 0.053

Refinement
  • R[F2 > 2σ(F2)] = 0.055

  • wR(F2) = 0.134

  • S = 0.91

  • 2851 reflections

  • 183 parameters

  • H-atom parameters constrained

  • Δρmax = 0.29 e Å−3

  • Δρmin = −0.24 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C3—H3⋯N4i 0.95 2.60 3.533 (2) 166
Symmetry code: (i) x-1, y, z-1.

Data collection: SMART (Bruker, 1998[Bruker (1998). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 1998[Bruker (1998). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; 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: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Comment top

Recently, the triazolo-annelated quinazoline compounds were found to display remarkable pharmacological activities (Alagarsamy et al., 2005, 2007). The novel 2-alkoxy-1,2,4-triazolo[1,5-a]quinazolines have been proven as excellent agents for controlling the plant growth diseases caused by fungal pathogen agents (Berezank et al., 2008a,b), and described as adenosine receptor antagonists (Al-Salahi et al., 2011). Furthermore, the bis-[1,2,4]triazolo[4,3 - a:4',3'-c]quinazoline has been reported to exhibit antitoxoplasmosis activity (El-Tombary et al., 1999). This work has done in continuation of our program with the aim of obtaining an interesting series of bis-[1,2,4]triazoloquinazolines compounds which could be expected to contribute as a pharmacophore to the bioactivity of their triazoloquinazoline parent compounds (Al-Salahi et al., 2009, 2010).

Related literature top

For the biological activity of quinazoline derviatives, see: Alagarsamy et al. (2005, 2007). For our study of the chemical and pharmacological properties of triazolo quinazoline derivatives, see: Al-Salahi (2009); Al-Salahi et al. (2010, 2011); Berezank et al. (2008a,b). For related structures, see: El-Tombary et al. (1999).

Experimental top

A mixture of 2-ethoxy-5-chloro-[1,2,4]triazolo[1,5-a]quinazoline (1 mmol) and acetohydrazide (2.2 mmol) was refluxed in absolute toluene (15 ml) in the presence of sodium hydride (0.8 mmol) for 18 h. The solvent was removed under reduced pressure, and the residue was crystallized from methanol to afford (C13H12N6O) as yellowish crystal.

Refinement top

All H atoms were positioned geometrically and refined using a riding model, with C—H = 0.95–0.98 Å. The displacement parameters are Uiso(H) = xUeq(C), where x = 1.2 or 1.5.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids for non-H atoms and the atom-numbering scheme.
2-Ethoxy-5-methylbis[1,2,4]triazolo[1,5-a:4',3'-c]quinazoline top
Crystal data top
C13H12N6OF(000) = 560
Mr = 268.29Dx = 1.420 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 210 reflections
a = 7.4121 (11) Åθ = 1.2–27.0°
b = 19.240 (3) ŵ = 0.10 mm1
c = 9.3096 (14) ÅT = 153 K
β = 109.051 (2)°Plate, colourless
V = 1254.9 (3) Å30.43 × 0.21 × 0.05 mm
Z = 4
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
2851 independent reflections
Radiation source: fine-focus sealed tube1817 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.053
ω scanθmax = 27.5°, θmin = 2.6°
Absorption correction: multi-scan
(SADABS; Bruker, 1998)
h = 99
Tmin = 0.959, Tmax = 0.995k = 2424
2851 measured reflectionsl = 011
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)] = 0.055Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.134H-atom parameters constrained
S = 0.91 w = 1/[σ2(Fo2) + (0.072P)2]
where P = (Fo2 + 2Fc2)/3
2851 reflections(Δ/σ)max = 0.044
183 parametersΔρmax = 0.29 e Å3
0 restraintsΔρmin = 0.24 e Å3
Crystal data top
C13H12N6OV = 1254.9 (3) Å3
Mr = 268.29Z = 4
Monoclinic, P21/cMo Kα radiation
a = 7.4121 (11) ŵ = 0.10 mm1
b = 19.240 (3) ÅT = 153 K
c = 9.3096 (14) Å0.43 × 0.21 × 0.05 mm
β = 109.051 (2)°
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
2851 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 1998)
1817 reflections with I > 2σ(I)
Tmin = 0.959, Tmax = 0.995Rint = 0.053
2851 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0550 restraints
wR(F2) = 0.134H-atom parameters constrained
S = 0.91Δρmax = 0.29 e Å3
2851 reflectionsΔρmin = 0.24 e Å3
183 parameters
Special details top

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) top
xyzUiso*/Ueq
O10.26808 (18)0.12586 (7)0.60062 (14)0.0292 (4)
N50.0311 (2)0.21218 (8)0.29706 (16)0.0243 (4)
N30.0101 (2)0.33173 (8)0.34526 (16)0.0244 (4)
N40.1812 (2)0.23979 (8)0.52010 (16)0.0233 (4)
N60.0364 (2)0.14887 (8)0.36339 (16)0.0265 (4)
N10.0267 (3)0.44495 (9)0.32026 (18)0.0375 (4)
N20.1545 (2)0.41376 (9)0.18987 (18)0.0360 (4)
C60.1751 (3)0.22080 (10)0.1548 (2)0.0263 (5)
C10.2270 (3)0.28941 (10)0.10826 (19)0.0273 (5)
C80.0587 (2)0.26359 (10)0.39243 (19)0.0223 (4)
C110.1609 (2)0.16942 (10)0.49439 (19)0.0232 (4)
C50.2620 (3)0.16363 (11)0.0665 (2)0.0322 (5)
H50.22680.11750.10030.039*
C70.1306 (3)0.34608 (11)0.20684 (19)0.0276 (5)
C40.4021 (3)0.17661 (12)0.0729 (2)0.0379 (6)
H40.46200.13860.13560.045*
C30.4562 (3)0.24455 (12)0.1222 (2)0.0379 (6)
H30.55230.25220.21740.045*
C90.0698 (3)0.39608 (10)0.4119 (2)0.0292 (5)
C20.3704 (3)0.30040 (12)0.0332 (2)0.0349 (5)
H20.40790.34640.06710.042*
C100.2187 (3)0.40648 (10)0.5633 (2)0.0336 (5)
H10A0.23260.45620.58680.050*
H10B0.34070.38770.56100.050*
H10C0.18050.38230.64140.050*
C120.2394 (3)0.05207 (10)0.5604 (2)0.0371 (5)
H12A0.26520.04320.46420.045*
H12B0.10590.03860.54650.045*
C130.3737 (3)0.01071 (11)0.6867 (2)0.0439 (6)
H13A0.50550.02380.69830.066*
H13B0.35560.03890.66280.066*
H13C0.34790.02020.78160.066*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0254 (7)0.0221 (8)0.0340 (7)0.0003 (6)0.0013 (6)0.0025 (6)
N50.0207 (8)0.0270 (10)0.0242 (8)0.0019 (7)0.0060 (6)0.0033 (7)
N30.0219 (8)0.0257 (10)0.0265 (8)0.0020 (7)0.0092 (7)0.0015 (7)
N40.0174 (8)0.0253 (10)0.0263 (8)0.0008 (7)0.0059 (7)0.0020 (7)
N60.0241 (8)0.0264 (10)0.0272 (8)0.0008 (7)0.0061 (7)0.0031 (7)
N10.0416 (11)0.0319 (11)0.0399 (10)0.0074 (9)0.0147 (8)0.0028 (8)
N20.0360 (10)0.0366 (12)0.0348 (9)0.0086 (9)0.0108 (8)0.0047 (8)
C60.0185 (9)0.0407 (13)0.0216 (9)0.0026 (9)0.0091 (7)0.0014 (9)
C10.0190 (9)0.0404 (13)0.0248 (9)0.0005 (9)0.0100 (8)0.0021 (8)
C80.0169 (9)0.0267 (11)0.0249 (9)0.0012 (8)0.0092 (8)0.0029 (8)
C110.0179 (9)0.0252 (11)0.0264 (9)0.0011 (8)0.0073 (7)0.0038 (8)
C50.0256 (10)0.0441 (14)0.0282 (10)0.0102 (10)0.0107 (8)0.0060 (9)
C70.0226 (10)0.0359 (13)0.0258 (9)0.0068 (9)0.0099 (8)0.0062 (9)
C40.0254 (11)0.0629 (17)0.0263 (10)0.0151 (11)0.0097 (9)0.0098 (10)
C30.0200 (10)0.0670 (17)0.0250 (10)0.0045 (11)0.0050 (8)0.0011 (10)
C90.0296 (11)0.0266 (12)0.0350 (10)0.0017 (9)0.0153 (9)0.0033 (9)
C20.0220 (10)0.0553 (15)0.0281 (10)0.0034 (10)0.0092 (9)0.0076 (10)
C100.0338 (12)0.0270 (12)0.0394 (11)0.0031 (10)0.0110 (9)0.0077 (9)
C120.0357 (12)0.0240 (12)0.0473 (12)0.0033 (10)0.0076 (10)0.0056 (10)
C130.0462 (14)0.0250 (13)0.0560 (14)0.0026 (10)0.0106 (11)0.0014 (10)
Geometric parameters (Å, º) top
O1—C111.341 (2)C5—C41.395 (3)
O1—C121.466 (2)C5—H50.9500
N5—C81.351 (2)C4—C31.400 (3)
N5—N61.383 (2)C4—H40.9500
N5—C61.414 (2)C3—C21.379 (3)
N3—C91.391 (2)C3—H30.9500
N3—C81.392 (2)C9—C101.493 (3)
N3—C71.395 (2)C2—H20.9500
N4—C81.320 (2)C10—H10A0.9800
N4—C111.375 (2)C10—H10B0.9800
N6—C111.327 (2)C10—H10C0.9800
N1—C91.313 (2)C12—C131.497 (3)
N1—N21.407 (2)C12—H12A0.9900
N2—C71.317 (3)C12—H12B0.9900
C6—C51.398 (3)C13—H13A0.9800
C6—C11.403 (3)C13—H13B0.9800
C1—C21.412 (3)C13—H13C0.9800
C1—C71.454 (3)
C11—O1—C12114.54 (14)C5—C4—H4119.4
C8—N5—N6108.83 (14)C3—C4—H4119.4
C8—N5—C6126.11 (16)C2—C3—C4120.26 (19)
N6—N5—C6125.03 (15)C2—C3—H3119.9
C9—N3—C8133.29 (16)C4—C3—H3119.9
C9—N3—C7105.59 (16)N1—C9—N3108.74 (17)
C8—N3—C7121.08 (16)N1—C9—C10126.52 (18)
C8—N4—C11100.42 (14)N3—C9—C10124.74 (17)
C11—N6—N5100.92 (14)C3—C2—C1120.2 (2)
C9—N1—N2108.99 (16)C3—C2—H2119.9
C7—N2—N1106.98 (15)C1—C2—H2119.9
C5—C6—C1122.08 (18)C9—C10—H10A109.5
C5—C6—N5121.37 (18)C9—C10—H10B109.5
C1—C6—N5116.54 (16)H10A—C10—H10B109.5
C6—C1—C2118.41 (18)C9—C10—H10C109.5
C6—C1—C7118.80 (16)H10A—C10—H10C109.5
C2—C1—C7122.79 (19)H10B—C10—H10C109.5
N4—C8—N5112.61 (16)O1—C12—C13108.09 (16)
N4—C8—N3129.94 (16)O1—C12—H12A110.1
N5—C8—N3117.45 (16)C13—C12—H12A110.1
N6—C11—O1123.95 (17)O1—C12—H12B110.1
N6—C11—N4117.22 (16)C13—C12—H12B110.1
O1—C11—N4118.83 (15)H12A—C12—H12B108.4
C4—C5—C6117.8 (2)C12—C13—H13A109.5
C4—C5—H5121.1C12—C13—H13B109.5
C6—C5—H5121.1H13A—C13—H13B109.5
N2—C7—N3109.70 (17)C12—C13—H13C109.5
N2—C7—C1130.31 (17)H13A—C13—H13C109.5
N3—C7—C1119.98 (17)H13B—C13—H13C109.5
C5—C4—C3121.25 (19)
C8—N5—N6—C110.41 (17)C8—N4—C11—O1178.70 (15)
C6—N5—N6—C11177.68 (15)C1—C6—C5—C41.1 (3)
C9—N1—N2—C70.1 (2)N5—C6—C5—C4179.63 (15)
C8—N5—C6—C5178.46 (16)N1—N2—C7—N30.09 (19)
N6—N5—C6—C50.7 (3)N1—N2—C7—C1178.94 (18)
C8—N5—C6—C10.9 (2)C9—N3—C7—N20.26 (19)
N6—N5—C6—C1178.64 (15)C8—N3—C7—N2178.22 (14)
C5—C6—C1—C20.6 (3)C9—N3—C7—C1178.89 (15)
N5—C6—C1—C2179.99 (15)C8—N3—C7—C10.9 (2)
C5—C6—C1—C7179.69 (16)C6—C1—C7—N2179.24 (17)
N5—C6—C1—C70.3 (2)C2—C1—C7—N21.1 (3)
C11—N4—C8—N50.72 (18)C6—C1—C7—N30.3 (2)
C11—N4—C8—N3180.00 (16)C2—C1—C7—N3179.94 (15)
N6—N5—C8—N40.8 (2)C6—C5—C4—C30.9 (3)
C6—N5—C8—N4177.30 (15)C5—C4—C3—C20.2 (3)
N6—N5—C8—N3179.86 (13)N2—N1—C9—N30.3 (2)
C6—N5—C8—N32.1 (2)N2—N1—C9—C10179.39 (17)
C9—N3—C8—N40.1 (3)C8—N3—C9—N1177.93 (16)
C7—N3—C8—N4177.21 (17)C7—N3—C9—N10.3 (2)
C9—N3—C8—N5179.34 (16)C8—N3—C9—C101.8 (3)
C7—N3—C8—N52.0 (2)C7—N3—C9—C10179.35 (16)
N5—N6—C11—O1179.07 (15)C4—C3—C2—C10.2 (3)
N5—N6—C11—N40.04 (19)C6—C1—C2—C30.0 (3)
C12—O1—C11—N60.7 (2)C7—C1—C2—C3179.65 (17)
C12—O1—C11—N4178.38 (14)C11—O1—C12—C13177.76 (15)
C8—N4—C11—N60.47 (19)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C3—H3···N4i0.952.603.533 (2)166
Symmetry code: (i) x1, y, z1.

Experimental details

Crystal data
Chemical formulaC13H12N6O
Mr268.29
Crystal system, space groupMonoclinic, P21/c
Temperature (K)153
a, b, c (Å)7.4121 (11), 19.240 (3), 9.3096 (14)
β (°) 109.051 (2)
V3)1254.9 (3)
Z4
Radiation typeMo Kα
µ (mm1)0.10
Crystal size (mm)0.43 × 0.21 × 0.05
Data collection
DiffractometerBruker SMART APEX CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 1998)
Tmin, Tmax0.959, 0.995
No. of measured, independent and
observed [I > 2σ(I)] reflections
2851, 2851, 1817
Rint0.053
(sin θ/λ)max1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.055, 0.134, 0.91
No. of reflections2851
No. of parameters183
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.29, 0.24

Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 1998), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C3—H3···N4i0.952.603.533 (2)166
Symmetry code: (i) x1, y, z1.
 

Acknowledgements

We wish to express our gratitude to the Department of Chemistry, X-ray crystallography division of Hamburg University for their valuable help in the determination of the X-ray crystal structure.

References

First citationAlagarsamy, V., Giridhar, R. & Yadav, M. R. (2005). Bioorg. Med. Chem. Lett. 15, 1877–1880.  Web of Science CrossRef PubMed CAS
First citationAlagarsamy, V., Solomon, V. R. & Murugan, M. (2007). Bioorg. Med. Chem. 15, 4009–4015.  Web of Science CrossRef PubMed CAS
First citationAl-Salahi, R. (2009). PhD dissertation, Hamburg University, Germany.
First citationAl-Salahi, R. & Geffken, D. (2010). Molecules, 15, 7016–7034.  CAS
First citationAl-Salahi, R., Geffken, D. & Koellner, M. (2011). Chem. Pharm. Bull. 59, 730–733.  Web of Science CAS PubMed
First citationBerezank, J. F., Chan, D., Geffken, D., Hanagan, M. A., Lepone, G. E., Pasteris, R. S. & Swan, T. (2008a). World patent WO 2008103357.
First citationBerezank, J. F., Chan, D., Geffken, D., Hanagan, M. A., Lepone, G. E., Pasteris, R. S. & Swan, T. (2008b). Chem. Abstr. 1042828.
First citationBruker (1998). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
First citationEl-Tombary, A. A., Ismail, K. A., Aboulwafa, O. M., Omar, A.-M., El-Azzouni, M. Z. & El-Mansoury, S. T. (1999). Farmaco, 54, 486–488.  Web of Science PubMed CAS
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals
First citationWestrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.  Web of Science CrossRef CAS IUCr Journals

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