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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

Di-n-butyl 4,4′-dihy­dr­oxy-3,3′-{[(3aRS,7aRS)-2,3,3a,4,5,6,7,7a-octa­hydro-1H-1,3-benzimidazole-1,3-di­yl]bis­­(methyl­ene)}dibenzoate

aDepartamento de Química, Universidad Nacional de Colombia, Ciudad Universitaria, Bogotá, Colombia, and bInstitute of Physics ASCR, v.v.i., Na Slovance 2, 182 21 Praha 8, Czech Republic
*Correspondence e-mail: ariverau@unal.edu.co

(Received 29 July 2011; accepted 2 August 2011; online 11 August 2011)

The complete molecule of the title compound, C31H42N2O6, is generated by crystallographic twofold symmetry, with one C atom lying on the axis. The dihedral angle between the aromatic rings is 57.03 (6)°. The central heterocyclic ring adopts a half-chair conformation. The mol­ecular conformation is stabilized by two intra­molecular O—H⋯N hydrogen bonds with the N atoms of the heterocyclic ring as the acceptors. In the crystal, mol­ecules are linked into chains along the c axis by non-classical C—H⋯O hydrogen bonds.

Related literature

For related structures, see: Rivera et al. (2010[Rivera, A., Quiroga, D., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2010). Acta Cryst. E66, o2643.], 2011[Rivera, A., Quiroga, D., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2011). Acta Cryst. E67, o1542.]); Giordano et al. (1999[Giordano, F., Bettini, R., Donini, C., Gazzaniga, A., Caira, M. R., Zhang, G. G. Z. & Grant, D. J. W. (1999). J. Pharm. Sci. 88, 1210-1216.]); Feng & Grant (2006[Feng, Y. & Grant, D. J. W. (2006). Pharm. Res. 23, 1608-1616.]). For background to this work see: Koll et al. (2001[Koll, A., Parasuk, V., Parasuk, W., Karpfen, A. & Wolschann, P. (2001). J. Mol. Struct. 700, 81-90.]); Filarowski et al. (2004[Filarowski, A., Koll, A., Karpfen, A. & Wolschann, P. (2004). Chem. Phys. 297, 323-332.]).

[Scheme 1]

Experimental

Crystal data
  • C31H42N2O6

  • Mr = 538.7

  • Monoclinic, C 2/c

  • a = 15.4471 (3) Å

  • b = 8.8103 (2) Å

  • c = 20.9374 (4) Å

  • β = 95.077 (2)°

  • V = 2838.27 (10) Å3

  • Z = 4

  • Cu Kα radiation

  • μ = 0.70 mm−1

  • T = 120 K

  • 0.38 × 0.28 × 0.20 mm

Data collection
  • Agilent Xcalibur diffractometer with an Atlas (Gemini ultra Cu) detector

  • Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2010[Agilent (2010). CrysAlis PRO. Agilent Technologies, Yarnton, England.]) Tmin = 0.868, Tmax = 1.00

  • 13938 measured reflections

  • 2533 independent reflections

  • 2157 reflections with I > 3σ(I)

  • Rint = 0.030

Refinement
  • R[F2 > 2σ(F2)] = 0.036

  • wR(F2) = 0.104

  • S = 1.73

  • 2533 reflections

  • 181 parameters

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

  • Δρmax = 0.20 e Å−3

  • Δρmin = −0.19 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C5—H5a⋯O1i 0.96 2.39 3.2393 (16) 148
O3—H3⋯N1 0.884 (18) 1.873 (18) 2.6859 (12) 152.0 (17)
Symmetry code: (i) [-x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{1\over 2}}].

Data collection: CrysAlis PRO (Agilent, 2010[Agilent (2010). CrysAlis PRO. Agilent Technologies, Yarnton, England.]); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR2002 (Burla et al., 2003[Burla, M. C., Camalli, M., Carrozzini, B., Cascarano, G. L., Giacovazzo, C., Polidori, G. & Spagna, R. (2003). J. Appl. Cryst. 36, 1103.]); program(s) used to refine structure: JANA2006 (Petříček et al., 2006[Petříček, V., Dušek, M. & Palatinus, L. (2006). JANA2006. Institute of Physics, Praha, Czech Republic.]); molecular graphics: DIAMOND (Brandenburg & Putz, 2005[Brandenburg, K. & Putz, H. (2005). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: JANA2006.

Supporting information


Comment top

Intramolecular hydrogen bonding interactions in Mannich bases lead to distortions in the aromatic rings due the existence of ortho-quinonoid resonance structures (Koll et al. 2001; Filarowski et al. 2004), which are evidenced in the bond and bond angle values. During our studies we have synthesized a series of symmetrical di-Mannich bases, by reaction between (2R,7R,11S,16S)-1,8,10,17-tetraazapentacyclo [8.8.1.18,17.02,7.011,16]icosane and p-halophenols. The intramolecular hydrogen bond interaction is weaker in the Mannich base having p-fluorine substituent [N···O 2.711 (2) Å] (Rivera et al. 2011) whereas in the case of the Mannich base p-chlorine substituted [N··· O 2.652 (2) Å] (Rivera et al. 2010), due to electron-withdrawing effect of chlorine atom. However, the distortion in the aromatic ring in these Mannich bases, leads to a conclusion indicating that the effect of halogen atoms seems to be no meaningful which can be explained on the basis of the presence of conjugative electron-release from lone pairs of halogen atom. To avoid the conjugation effect of halogen to aromatic ring we synthesized the title compound (I) which is a racemic Mannich base with a non-halogen electron withdrawing group in para position. The molecular structure and atom-numbering scheme for (I) are shown in Fig. 1. The X-ray diffraction analysis shows the existence of two intramolecular hydrogen bonding interactions between the hydroxy H atom and the amine groups in the heterocyclic ring (table 1).

The observed C11—O3 bond length [1.358 (2)Å] is in good agreement with the p-chlorophenol derivative (Rivera, et al. 2010) but is shorter by 0.01 Å in comparison with p-fluorophenol derivative (Rivera, et al. 2011). Though, in the title compound the X-ray analysis revealed the existence of distortions of the phenol ring in comparison with the related structures (Rivera et al. 2010, 2011), which was evident from the elongation of the C8—C9 bond length in title compound from [1.381 (2) Å, Rivera et al. 2011] to 1.393 (2) Å.

In comparison with the crystal packing of butylparaben, there are not head-to-tail hydrogen bonding interactions inside the chains that involve the O—H group as donor and the carbonyl O atom as acceptor (Giordano et al. 1999; Feng & Grant, 2006), there are non-classical hydrogen bonds C5—H5a··· O1 (table 1) which link neighboring helps stabilize the packing along c axis (Fig. 2).

Related literature top

For related structures, see: Rivera et al. (2010, 2011); Giordano et al. (1999); Feng & Grant (2006). For background to this work see: Koll et al. (2001); Filarowski et al. (2004).

Experimental top

A solution of (2R,7R,11S,16S)-1,8,10,17-tetraazapentacyclo [8.8.1.18,\17.02,7.011,16] icosane (276 mg, 1.00 mmol) in dioxane (3 ml) and water (4 ml), previously prepared following described procedures, was added dropwise in a dioxane solution (3 ml) containing two equivalents of n-butyl 4-hydroxybenzoate (388 mg, 2.00 mmol) in a two-necked round-bottomed flask. The mixture was refluxed for about 12 h and then the solvent was evaporated under reduced pressure until a sticky residue appeared. The product was purified by chromatography on a silica column, and subjected to gradient elution with benzene:ethyl acetate (yield 19%, m.p. = 414–416 K). Single crystals of racemic (I) were grown from a chloroform solution by slow evaporation of the solvent at room temperature over a period of about 2 weeks.

Refinement top

All hydrogen atoms were discernible in difference Fourier maps and could be refined to reasonable geometry. According to common practice H atoms bonded C atoms were kept in ideal positions with C–H distance 0.96 Å during the refinement. The methyl H atoms were allowed to rotate freely about the adjacent C—C bonds. The hydroxyl H atoms were found in difference Fourier maps and their coordinates were refined freely. All H atoms were refined with displacement coefficients Uiso(H) set to 1.5Ueq(C, O) for methyl and hydroxyl groups and to to 1.2Ueq(C) for the CH– and CH2- groups.

Computing details top

Data collection: CrysAlis PRO (Agilent, 2010); cell refinement: CrysAlis PRO (Agilent, 2010); data reduction: CrysAlis PRO (Agilent, 2010); program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: JANA2006 (Petříček et al., 2006); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: JANA2006 (Petříček et al., 2006).

Figures top
[Figure 1] Fig. 1. A view of (I) with the numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. Packing of the molecules of the title compound view along b axis.
Di-n-butyl 4,4'-dihydroxy-3,3'-{[(3aRS,7aRS)-2,3,3a,4,5,6,7,7a-octahydro- 1H-1,3-benzimidazole-1,3-diyl]bis(methylene)}dibenzoate top
Crystal data top
C31H42N2O6F(000) = 1160
Mr = 538.7Dx = 1.260 Mg m3
Monoclinic, C2/cCu Kα radiation, λ = 1.5418 Å
Hall symbol: -C 2ycCell parameters from 7161 reflections
a = 15.4471 (3) Åθ = 2.9–67.0°
b = 8.8103 (2) ŵ = 0.70 mm1
c = 20.9374 (4) ÅT = 120 K
β = 95.077 (2)°Prism, colourless
V = 2838.27 (10) Å30.38 × 0.28 × 0.20 mm
Z = 4
Data collection top
Agilent Xcalibur
diffractometer with an Atlas (Gemini ultra Cu) detector
2533 independent reflections
Radiation source: Enhance Ultra (Cu) X-ray Source2157 reflections with I > 3σ(I)
Mirror monochromatorRint = 0.030
Detector resolution: 10.3784 pixels mm-1θmax = 67.2°, θmin = 4.2°
Rotation method data acquisition using ω scansh = 1718
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2010)
k = 1010
Tmin = 0.868, Tmax = 1l = 2424
13938 measured reflections
Refinement top
Refinement on F2H atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.036Weighting scheme based on measured s.u.'s w = 1/[σ2(I) + 0.0016I2]
wR(F2) = 0.104(Δ/σ)max = 0.009
S = 1.73Δρmax = 0.20 e Å3
2533 reflectionsΔρmin = 0.19 e Å3
181 parametersExtinction correction: B-C type 1 Lorentzian isotropic (Becker & Coppens, 1974)
0 restraintsExtinction coefficient: 2400 (500)
81 constraints
Crystal data top
C31H42N2O6V = 2838.27 (10) Å3
Mr = 538.7Z = 4
Monoclinic, C2/cCu Kα radiation
a = 15.4471 (3) ŵ = 0.70 mm1
b = 8.8103 (2) ÅT = 120 K
c = 20.9374 (4) Å0.38 × 0.28 × 0.20 mm
β = 95.077 (2)°
Data collection top
Agilent Xcalibur
diffractometer with an Atlas (Gemini ultra Cu) detector
2533 independent reflections
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2010)
2157 reflections with I > 3σ(I)
Tmin = 0.868, Tmax = 1Rint = 0.030
13938 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0360 restraints
wR(F2) = 0.104H atoms treated by a mixture of independent and constrained refinement
S = 1.73Δρmax = 0.20 e Å3
2533 reflectionsΔρmin = 0.19 e Å3
181 parameters
Special details top

Experimental. CrysAlisPro (Agilent Technologies, 2010) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F2 for refinement carried out on F and F2, respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement.

The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.16850 (6)0.28700 (12)0.16508 (5)0.0355 (3)
O20.23006 (6)0.43687 (10)0.09549 (4)0.0246 (3)
O30.47351 (6)0.13568 (10)0.08411 (4)0.0251 (3)
N10.45250 (4)0.23982 (9)0.20231 (3)0.0195 (3)
C10.50.13860 (11)0.250.0198 (5)
C20.45565 (8)0.39174 (13)0.23189 (6)0.0198 (4)
C30.44634 (8)0.52666 (14)0.18685 (6)0.0254 (4)
C40.45780 (9)0.67130 (15)0.22757 (7)0.0299 (4)
C50.36225 (8)0.19088 (14)0.18416 (6)0.0224 (4)
C60.35796 (8)0.04774 (14)0.14442 (6)0.0198 (3)
C70.29735 (8)0.06379 (14)0.15343 (6)0.0207 (4)
C80.28954 (8)0.19235 (14)0.11452 (6)0.0209 (4)
C90.34430 (8)0.20849 (15)0.06556 (6)0.0219 (4)
C100.40580 (8)0.09904 (15)0.05580 (6)0.0226 (4)
C110.41305 (8)0.02913 (14)0.09496 (6)0.0208 (4)
C120.22324 (8)0.30676 (15)0.12800 (6)0.0227 (4)
C130.16944 (8)0.55491 (14)0.11005 (7)0.0258 (4)
C140.17797 (8)0.68569 (14)0.06461 (6)0.0235 (4)
C150.12183 (9)0.81927 (15)0.08138 (7)0.0289 (4)
C160.12224 (10)0.94748 (16)0.03283 (7)0.0347 (4)
H1a0.5408830.0781710.229150.0238*
H20.4068570.4053280.2567060.0237*
H3a0.4906960.5224440.1575480.0305*
H3b0.3894360.5260220.1643210.0305*
H4a0.4089280.6830290.2524530.0359*
H4b0.4569890.7583070.199920.0359*
H5a0.3329440.1748850.2221580.0269*
H5b0.3313660.2706070.160660.0269*
H70.2597480.0524980.187260.0249*
H90.3392640.2963690.0383820.0263*
H100.4435060.1112270.0220940.0271*
H13a0.1828640.5889870.1533440.0309*
H13b0.1112480.5158060.1046550.0309*
H14a0.1610070.6532440.0215410.0281*
H14b0.237650.7170930.0663640.0281*
H15a0.0632470.7853250.0842610.0346*
H15b0.1417650.8568080.1231540.0346*
H16a0.0876191.0301540.0462010.0521*
H16b0.1808150.9815290.0299940.0521*
H16c0.0985610.9117150.008380.0521*
H30.4785 (11)0.193 (2)0.1188 (9)0.0376*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0375 (6)0.0326 (6)0.0388 (6)0.0083 (4)0.0174 (5)0.0107 (4)
O20.0237 (4)0.0207 (5)0.0297 (5)0.0030 (3)0.0044 (4)0.0042 (4)
O30.0297 (5)0.0239 (5)0.0220 (5)0.0055 (4)0.0045 (4)0.0015 (4)
N10.0209 (5)0.0171 (5)0.0198 (5)0.0000 (4)0.0019 (4)0.0003 (4)
C10.0220 (8)0.0160 (8)0.0210 (8)00.0007 (7)0
C20.0217 (6)0.0169 (6)0.0204 (6)0.0003 (5)0.0007 (5)0.0012 (5)
C30.0275 (6)0.0205 (7)0.0270 (7)0.0003 (5)0.0044 (5)0.0025 (5)
C40.0348 (8)0.0188 (7)0.0345 (7)0.0021 (5)0.0062 (6)0.0024 (5)
C50.0191 (6)0.0228 (7)0.0246 (6)0.0008 (5)0.0016 (5)0.0045 (5)
C60.0197 (6)0.0207 (6)0.0180 (6)0.0040 (4)0.0036 (5)0.0005 (5)
C70.0186 (6)0.0238 (7)0.0194 (6)0.0032 (5)0.0001 (5)0.0010 (5)
C80.0217 (6)0.0200 (7)0.0202 (6)0.0025 (5)0.0015 (5)0.0007 (5)
C90.0266 (6)0.0201 (6)0.0186 (6)0.0030 (5)0.0004 (5)0.0018 (5)
C100.0263 (6)0.0239 (7)0.0177 (6)0.0014 (5)0.0030 (5)0.0005 (5)
C110.0207 (6)0.0218 (7)0.0193 (6)0.0013 (5)0.0019 (5)0.0031 (5)
C120.0236 (6)0.0234 (7)0.0209 (6)0.0013 (5)0.0002 (5)0.0028 (5)
C130.0230 (6)0.0229 (7)0.0320 (7)0.0032 (5)0.0055 (5)0.0006 (5)
C140.0237 (6)0.0209 (7)0.0251 (7)0.0001 (5)0.0011 (5)0.0003 (5)
C150.0264 (7)0.0222 (7)0.0382 (8)0.0002 (5)0.0039 (6)0.0005 (6)
C160.0362 (8)0.0239 (7)0.0432 (8)0.0042 (6)0.0019 (6)0.0033 (6)
Geometric parameters (Å, º) top
O1—C121.2100 (17)C6—C71.3816 (17)
O2—C121.3421 (15)C6—C111.4070 (17)
O2—C131.4498 (16)C7—C81.3943 (17)
O3—C111.3575 (15)C7—H70.96
O3—H30.884 (18)C8—C91.3928 (18)
N1—C11.4836 (9)C8—C121.4818 (18)
N1—C21.4738 (14)C9—C101.3815 (18)
N1—C51.4765 (13)C9—H90.96
C1—H1a0.96C10—C111.3941 (17)
C1—H1ai0.96C10—H100.96
C2—C2i1.5061 (16)C13—C141.5074 (18)
C2—C31.5163 (17)C13—H13a0.96
C2—H20.96C13—H13b0.96
C3—C41.5347 (18)C14—C151.5213 (18)
C3—H3a0.96C14—H14a0.96
C3—H3b0.96C14—H14b0.96
C4—C4i1.5381 (19)C15—C161.520 (2)
C4—H4a0.96C15—H15a0.96
C4—H4b0.96C15—H15b0.96
C5—C61.5090 (17)C16—H16a0.96
C5—H5a0.96C16—H16b0.96
C5—H5b0.96C16—H16c0.96
C12—O2—C13115.15 (10)C8—C7—H7119.2486
C11—O3—H3105.7 (12)C7—C8—C9119.09 (11)
C1—N1—C2105.49 (7)C7—C8—C12117.83 (11)
C1—N1—C5113.40 (7)C9—C8—C12123.08 (11)
C2—N1—C5111.64 (8)C8—C9—C10120.53 (11)
N1—C1—N1i106.10 (7)C8—C9—H9119.7338
N1—C1—H1a109.4715C10—C9—H9119.7345
N1—C1—H1ai109.4713C9—C10—C11119.93 (12)
N1i—C1—H1a109.4713C9—C10—H10120.0369
N1i—C1—H1ai109.4715C11—C10—H10120.0376
H1a—C1—H1ai112.6412O3—C11—C6120.83 (11)
N1—C2—C2i101.91 (9)O3—C11—C10118.84 (11)
N1—C2—C3116.92 (9)C6—C11—C10120.33 (11)
N1—C2—H2110.0241O1—C12—O2122.61 (12)
C2i—C2—C3110.19 (10)O1—C12—C8123.94 (12)
C2i—C2—H2116.771O2—C12—C8113.44 (11)
C3—C2—H2101.7125O2—C13—C14108.75 (11)
C2—C3—C4107.78 (10)O2—C13—H13a109.4715
C2—C3—H3a109.471O2—C13—H13b109.4713
C2—C3—H3b109.4714C14—C13—H13a109.4714
C4—C3—H3a109.4714C14—C13—H13b109.4715
C4—C3—H3b109.472H13a—C13—H13b110.1822
H3a—C3—H3b111.1071C13—C14—C15111.23 (11)
C3—C4—C4i112.90 (11)C13—C14—H14a109.4707
C3—C4—H4a109.4707C13—C14—H14b109.4712
C3—C4—H4b109.4703C15—C14—H14a109.4716
C4i—C4—H4a109.4719C15—C14—H14b109.4715
C4i—C4—H4b109.4713H14a—C14—H14b107.6531
H4a—C4—H4b105.8086C14—C15—C16112.60 (12)
N1—C5—C6112.36 (10)C14—C15—H15a109.4712
N1—C5—H5a109.4714C14—C15—H15b109.4717
N1—C5—H5b109.4706C16—C15—H15a109.4711
C6—C5—H5a109.4712C16—C15—H15b109.4712
C6—C5—H5b109.4714H15a—C15—H15b106.1546
H5a—C5—H5b106.42C15—C16—H16a109.4718
C5—C6—C7121.09 (11)C15—C16—H16b109.4721
C5—C6—C11120.22 (11)C15—C16—H16c109.4718
C7—C6—C11118.62 (11)H16a—C16—H16b109.4713
C6—C7—C8121.50 (11)H16a—C16—H16c109.4705
C6—C7—H7119.2469H16b—C16—H16c109.4698
Symmetry code: (i) x+1, y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C5—H5a···O1ii0.962.393.2393 (16)148
O3—H3···N10.884 (18)1.873 (18)2.6859 (12)152.0 (17)
Symmetry code: (ii) x+1/2, y1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC31H42N2O6
Mr538.7
Crystal system, space groupMonoclinic, C2/c
Temperature (K)120
a, b, c (Å)15.4471 (3), 8.8103 (2), 20.9374 (4)
β (°) 95.077 (2)
V3)2838.27 (10)
Z4
Radiation typeCu Kα
µ (mm1)0.70
Crystal size (mm)0.38 × 0.28 × 0.20
Data collection
DiffractometerAgilent Xcalibur
diffractometer with an Atlas (Gemini ultra Cu) detector
Absorption correctionMulti-scan
(CrysAlis PRO; Agilent, 2010)
Tmin, Tmax0.868, 1
No. of measured, independent and
observed [I > 3σ(I)] reflections
13938, 2533, 2157
Rint0.030
(sin θ/λ)max1)0.598
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.036, 0.104, 1.73
No. of reflections2533
No. of parameters181
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.20, 0.19

Computer programs: CrysAlis PRO (Agilent, 2010), SIR2002 (Burla et al., 2003), JANA2006 (Petříček et al., 2006), DIAMOND (Brandenburg & Putz, 2005).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C5—H5a···O1i0.962.393.2393 (16)147.73
O3—H3···N10.884 (18)1.873 (18)2.6859 (12)152.0 (17)
Symmetry code: (i) x+1/2, y1/2, z+1/2.
 

Acknowledgements

We acknowledge the Dirección de Investigaciones, Sede Bogotá (DIB) de la Universidad Nacional de Colombia, for financial support of this work, as well as the Institutional Research Plan No. AVOZ10100521 of the Institute of Physics and the Praemium Academiae Project of the Academy of Sciences of the Czech Republic. DQ acknowledges the Vicerrectoría Académica de la Universidad Nacional de Colombia for a fellowship.

References

First citationAgilent (2010). CrysAlis PRO. Agilent Technologies, Yarnton, England.  Google Scholar
First citationBrandenburg, K. & Putz, H. (2005). DIAMOND. Crystal Impact GbR, Bonn, Germany.  Google Scholar
First citationBurla, M. C., Camalli, M., Carrozzini, B., Cascarano, G. L., Giacovazzo, C., Polidori, G. & Spagna, R. (2003). J. Appl. Cryst. 36, 1103.  CrossRef IUCr Journals Google Scholar
First citationFeng, Y. & Grant, D. J. W. (2006). Pharm. Res. 23, 1608–1616.  Web of Science CrossRef PubMed CAS Google Scholar
First citationFilarowski, A., Koll, A., Karpfen, A. & Wolschann, P. (2004). Chem. Phys. 297, 323–332.  CrossRef CAS Google Scholar
First citationGiordano, F., Bettini, R., Donini, C., Gazzaniga, A., Caira, M. R., Zhang, G. G. Z. & Grant, D. J. W. (1999). J. Pharm. Sci. 88, 1210–1216.  CrossRef CAS Google Scholar
First citationKoll, A., Parasuk, V., Parasuk, W., Karpfen, A. & Wolschann, P. (2001). J. Mol. Struct. 700, 81–90.  Google Scholar
First citationPetříček, V., Dušek, M. & Palatinus, L. (2006). JANA2006. Institute of Physics, Praha, Czech Republic.  Google Scholar
First citationRivera, A., Quiroga, D., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2010). Acta Cryst. E66, o2643.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationRivera, A., Quiroga, D., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2011). Acta Cryst. E67, o1542.  Web of Science CSD CrossRef 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.

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