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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 65| Part 11| November 2009| Page o2717
https://doi.org/10.1107/S1600536809040793

Imidazolium fumarate

Rodolfo Moreno-Fuquen,a* Javier Ellenab and Jahyr E. Theodorob

aDepartamento de Química - Facultad de Ciencias, Universidad del Valle, Apartado 25360, Santiago de Cali, Colombia, and bInstituto de Física de São Carlos, Universidade de São Paulo, USP, São Carlos, SP, Brazil
*Correspondence e-mail: rodimo26@yahoo.es

(Received 28 September 2009; accepted 6 October 2009; online 13 October 2009)

In the title compound, C3H5N2+·C4H3O4−, the dihedral angle between the imidazolium ring and the plane formed by the fumarate anion is 80.98 (6)°. In the crystal structure, inter­molecular O—H⋯O and N—H⋯O hydrogen bonds form extended chains along [100] and [01[\overline{1}]], creating a two-dimensional network.

Related literature

For background information on the anti-pyretic and anti-inflamatory biological activity of imidazole derivatives, see: Tudek et al. (1992[Tudek, B., Boiteux, S. & Laval, J. (1992). Nucleic Acid Res. 20, 3079-3084.]); Puig-Parellada et al. (1973[Puig-Parellada, P., Garcia-Gasulla, G. & Puig-Muset, P. (1973). Pharmacology, 10, 161-168.]). For fumaric acid, see: Bednowitz & Post (1966[Bednowitz, A. L. & Post, B. (1966). Acta Cryst. 21, 566-571.]) and for imidazole, see: McMullan et al. (1979[McMullan, R. K., Epstein, J., Ruble, J. R. & Craven, B. M. (1979). Acta Cryst. B35, 688-691.]). For hydrogen-bond motifs, see: Etter (1990[Etter, M. (1990). Acc. Chem. Res. 23, 120-126.]).

[Scheme 1]

Experimental

Crystal data

  • C3H5N2+·C4H3O4−

  • Mr = 184.15

  • Triclinic, [P \overline 1]

  • a = 7.4794 (4) Å

  • b = 7.7522 (3) Å

  • c = 8.4231 (4) Å

  • α = 69.695 (3)°

  • β = 81.415 (2)°

  • γ = 66.193 (2)°

  • V = 419.04 (3) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.12 mm−1

  • T = 294 K

  • 0.12 × 0.02 × 0.02 mm
Data collection

  • Nonius KappaCCD diffractometer

  • Absorption correction: none

  • 7824 measured reflections

  • 1922 independent reflections

  • 1443 reflections with I > 2σ(I)

  • Rint = 0.087
Refinement

  • R[F2 > 2σ(F2)] = 0.051

  • wR(F2) = 0.149

  • S = 1.07

  • 1922 reflections

  • 118 parameters

  • H-atom parameters constrained

  • Δρmax = 0.31 e Å−3

  • Δρmin = −0.29 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A D⋯A D—H⋯A
O1—H1⋯O4i 0.82 1.75 2.5699 (16) 173
N2—H8⋯O3ii 0.86 1.82 2.6600 (18) 166
N1—H9⋯O4iii 0.86 1.94 2.7969 (16) 172
Symmetry codes: (i) x+1, y, z; (ii) -x+1, -y+1, -z; (iii) -x+1, -y, -z+1.

Data collection: COLLECT (Nonius, 2000[Nonius (2000). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: SCALEPACK (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); data reduction: DENZO (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]) and SCALEPACK; 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 for Windows (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]) and Mercury (Macrae et al., 2006[Macrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor, R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453-457.]); software used to prepare material for publication: PARST95 (Nardelli, 1995[Nardelli, M. (1995). J. Appl. Cryst. 28, 659.]).

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536809040793/lh2920sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536809040793/lh2920Isup2.hkl

checkCIF report


Comment top

This work is part of a series of studies on the structural behavior of imidazole derivatives. Imidazole molecule is a heterocyclic compound which is present in important biological building blocks such as histidine, histamine, guanine (Tudek et al., 1992). The analgesic, anti-inflammatory and anti pyretic properties of imidazole have been reported (Puig-Parellada et al., 1973). In search of systems that form cyclic motifs linked by intermolecular hydrogen bonds, our research group focused its attention on the structural properties of molecular complex formed by fumaric acid (FUM) and imidazole (IM) moieties (I). The general crystallographic behavior of fumaric acid (Bednowitz & Post, 1966) and the imidazole free molecules (McMullan, et al., 1979) may be used as reference systems in order to compare to the title imidazolium salt. A displacement ellipsoid plot of (I) with the atomic numbering scheme is shown in Figure 1. The free molecule of fumaric acid as well as other organic acids, are characterized by forming dimers in their structures. In the formation of the title adduct (I), dimers of fumaric acid decompose, to gain new and stronger hydrogen bonds and a more stable structure with imidazole moiety (see Table 1), (Nardelli, 1995). The C4–O4 bond length changes from 1.290 (5) in free fumaric acid molecule (Bednowitz & Post, 1966) to 1.2664 (17) Å in (I). The title structure shows a dihedral angle of 80.98 (6)° between the imidazole ring and the plane formed by FUM molecule. The other bond lengths and bond angles of (I) are in good agreement with the standard values and correspond to those observed in the free molecules. The transference of the proton from one of the carboxylic acid groups of FUM molecule to the basic N-atom of the IM molecule is carried out. This proton transfer allows the formation of new interactions in the FUM-IM adduct. The title adduct is characterized by the formation of hydrogen-bond interactions between O—H···O and N—H···O. One of the strongest hydrogen bond O—H···O interaction is responsible for crystal growth in [100] direction. Indeed, in a first substructure, atom O4 in the molecule at (x, y, z) acts as hydrogen bond donor to carboxyl O1i atom in the molecule at (x + 1, y, z). The propagation of this interaction forms a C(7) (Etter, 1990) chain running along [100] direction (Fig. 2). In a second substructure, atom N2ii in the molecule at (-x + 1, -y + 1, -z) acts as hydrogen bond donor to the atom O3 in the molecule at (x, y, z). While the atom N1i in the molecule at (-x + 1, -y, -z + 1) acts as hydrogen bond donor to carboxy O4 atom in the molecule at (x, y, z). These interactions form C(8) chains which are running parallel to the [01–1] direction (Fig.3). All of these interactions in [100], and [01–1] directions define the overall two dimensional network.

Related literature top

For background information on the anti-pyretic and anti-inflamatory biological activity of imidazole derivatives, see: Tudek et al. (1992); Puig-Parellada et al. (1973). For fumaric acid, see: Bednowitz & Post (1966) and for imidazole, see: McMullan et al. (1979). For hydrogen-bond motifs, see: Etter (1990).

Experimental top

The synthesis of the title adduct (I) was carried out by slow evaporation of equimolar quantities of fumaric acid (0.739 g, 637 mmol) and imidazole (0.433 g,) in 100 ml of aqueous solution of methyl alcohol at 2%. After 3 days, colourless prisms of poor quality, with a melting point greater than 424 K, were formed. Crystalline sample decomposes at temperatures greater than this value. The initial reagents were purchased from Aldrich Chemical Co., and were used as received.

Refinement top

All H-atoms were located from difference maps and were positioned geometrically and refined using a riding model with (C—H= 0.93, N—H= 0.86 and O—H= 0.82 A°) and Uiso(H) (in the range 1.2–1.5 times Ueq of the parent atom).

Structure description top

This work is part of a series of studies on the structural behavior of imidazole derivatives. Imidazole molecule is a heterocyclic compound which is present in important biological building blocks such as histidine, histamine, guanine (Tudek et al., 1992). The analgesic, anti-inflammatory and anti pyretic properties of imidazole have been reported (Puig-Parellada et al., 1973). In search of systems that form cyclic motifs linked by intermolecular hydrogen bonds, our research group focused its attention on the structural properties of molecular complex formed by fumaric acid (FUM) and imidazole (IM) moieties (I). The general crystallographic behavior of fumaric acid (Bednowitz & Post, 1966) and the imidazole free molecules (McMullan, et al., 1979) may be used as reference systems in order to compare to the title imidazolium salt. A displacement ellipsoid plot of (I) with the atomic numbering scheme is shown in Figure 1. The free molecule of fumaric acid as well as other organic acids, are characterized by forming dimers in their structures. In the formation of the title adduct (I), dimers of fumaric acid decompose, to gain new and stronger hydrogen bonds and a more stable structure with imidazole moiety (see Table 1), (Nardelli, 1995). The C4–O4 bond length changes from 1.290 (5) in free fumaric acid molecule (Bednowitz & Post, 1966) to 1.2664 (17) Å in (I). The title structure shows a dihedral angle of 80.98 (6)° between the imidazole ring and the plane formed by FUM molecule. The other bond lengths and bond angles of (I) are in good agreement with the standard values and correspond to those observed in the free molecules. The transference of the proton from one of the carboxylic acid groups of FUM molecule to the basic N-atom of the IM molecule is carried out. This proton transfer allows the formation of new interactions in the FUM-IM adduct. The title adduct is characterized by the formation of hydrogen-bond interactions between O—H···O and N—H···O. One of the strongest hydrogen bond O—H···O interaction is responsible for crystal growth in [100] direction. Indeed, in a first substructure, atom O4 in the molecule at (x, y, z) acts as hydrogen bond donor to carboxyl O1i atom in the molecule at (x + 1, y, z). The propagation of this interaction forms a C(7) (Etter, 1990) chain running along [100] direction (Fig. 2). In a second substructure, atom N2ii in the molecule at (-x + 1, -y + 1, -z) acts as hydrogen bond donor to the atom O3 in the molecule at (x, y, z). While the atom N1i in the molecule at (-x + 1, -y, -z + 1) acts as hydrogen bond donor to carboxy O4 atom in the molecule at (x, y, z). These interactions form C(8) chains which are running parallel to the [01–1] direction (Fig.3). All of these interactions in [100], and [01–1] directions define the overall two dimensional network.

For background information on the anti-pyretic and anti-inflamatory biological activity of imidazole derivatives, see: Tudek et al. (1992); Puig-Parellada et al. (1973). For fumaric acid, see: Bednowitz & Post (1966) and for imidazole, see: McMullan et al. (1979). For hydrogen-bond motifs, see: Etter (1990).

Computing details top

Data collection: COLLECT (Nonius, 2000); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: PARST95 (Nardelli, 1995).

Figures top
[Figure 1] Fig. 1. An ORTEP-3 (Farrugia, 1997) perspective drawing of (I), with the atomic labelling scheme for non-H atoms, which are represented by displacement ellipsoids drawn at the 50% probability level and, for the sake of clarity, H atoms are shown as spheres of arbitrary radius.
[Figure 2] Fig. 2. Part of the crystal structure of (I), showing the formation of C(7) chains running along [100] direction. Symmetry code: (i) x + 1, y, z; (ii) x - 1, y, z
[Figure 3] Fig. 3. Part of the crystal structure of (I), showing the formation of C(8) chains running along [01–1]. Symmetry code: (i) -x + 1, -y, -z + 1; (ii) -x + 1, -y + 1, -z
Imidazolium fumarate top
Crystal data top
C3H5N2+·C4H3O4−Z = 2
Mr = 184.15F(000) = 192
Triclinic, P1Dx = 1.460 Mg m−3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 7.4794 (4) ÅCell parameters from 4127 reflections
b = 7.7522 (3) Åθ = 2.6–27.5°
c = 8.4231 (4) ŵ = 0.12 mm−1
α = 69.695 (3)°T = 294 K
β = 81.415 (2)°Prism, colourless
γ = 66.193 (2)°0.12 × 0.02 × 0.02 mm
V = 419.04 (3) Å3
Data collection top
Nonius KappaCCD
diffractometer		1443 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.087
Graphite monochromatorθmax = 27.5°, θmin = 2.6°
CCD rotation images, thick slices scansh = −9→8
7824 measured reflectionsk = −10→10
1922 independent reflectionsl = −10→10
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)] = 0.051Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.149H-atom parameters constrained
S = 1.07 w = 1/[σ2(Fo2) + (0.0832P)2 + 0.0432P]
where P = (Fo2 + 2Fc2)/3
1922 reflections(Δ/σ)max < 0.001
118 parametersΔρmax = 0.31 e Å−3
0 restraintsΔρmin = −0.29 e Å−3
Crystal data top
C3H5N2+·C4H3O4−γ = 66.193 (2)°
Mr = 184.15V = 419.04 (3) Å3
Triclinic, P1Z = 2
a = 7.4794 (4) ÅMo Kα radiation
b = 7.7522 (3) ŵ = 0.12 mm−1
c = 8.4231 (4) ÅT = 294 K
α = 69.695 (3)°0.12 × 0.02 × 0.02 mm
β = 81.415 (2)°
Data collection top
Nonius KappaCCD
diffractometer		1443 reflections with I > 2σ(I)
7824 measured reflectionsRint = 0.087
1922 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0510 restraints
wR(F2) = 0.149H-atom parameters constrained
S = 1.07Δρmax = 0.31 e Å−3
1922 reflectionsΔρmin = −0.29 e Å−3
118 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
O40.06367 (15)0.14005 (15)0.66024 (12)0.0409 (3)
O20.71272 (18)0.03156 (19)0.86710 (14)0.0507 (4)
O10.71448 (18)0.2024 (2)0.59326 (14)0.0592 (4)
H10.82240.19130.61570.089*
O30.0768 (2)0.3167 (2)0.39170 (14)0.0587 (4)
N10.8197 (2)0.25796 (19)0.13620 (16)0.0466 (4)
H90.84730.13970.20630.056*
N20.8081 (2)0.4960 (2)−0.09082 (16)0.0443 (4)
H80.82670.5605−0.19370.053*
C20.4385 (2)0.1246 (2)0.70462 (18)0.0380 (4)
H20.37700.06240.79740.046*
C40.1475 (2)0.2259 (2)0.53479 (17)0.0365 (4)
C10.6358 (2)0.1144 (2)0.72978 (18)0.0373 (4)
C30.3458 (2)0.2155 (2)0.56046 (18)0.0415 (4)
H30.40730.27780.46780.050*
C50.8781 (3)0.3027 (2)−0.0231 (2)0.0475 (4)
H50.95600.2119−0.07810.057*
C60.7006 (3)0.5786 (2)0.0293 (2)0.0493 (4)
H60.63420.71350.01470.059*
C70.7089 (3)0.4285 (3)0.1717 (2)0.0485 (4)
H70.65000.43910.27510.058*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O40.0376 (6)0.0512 (6)0.0305 (6)−0.0243 (5)−0.0008 (4)0.0002 (5)
O20.0456 (7)0.0681 (8)0.0344 (6)−0.0282 (6)−0.0079 (5)−0.0006 (5)
O10.0435 (7)0.0886 (9)0.0388 (7)−0.0404 (7)−0.0064 (5)0.0083 (6)
O30.0548 (8)0.0869 (9)0.0302 (6)−0.0419 (7)−0.0100 (5)0.0079 (6)
N10.0564 (9)0.0408 (7)0.0368 (7)−0.0217 (7)−0.0059 (6)0.0006 (5)
N20.0499 (8)0.0517 (8)0.0288 (6)−0.0259 (7)−0.0019 (6)−0.0012 (5)
C20.0358 (8)0.0450 (8)0.0334 (7)−0.0207 (7)0.0019 (6)−0.0072 (6)
C40.0369 (8)0.0428 (7)0.0278 (7)−0.0196 (6)−0.0013 (6)−0.0033 (6)
C10.0354 (8)0.0427 (7)0.0317 (7)−0.0180 (6)−0.0013 (6)−0.0051 (6)
C30.0380 (8)0.0550 (9)0.0317 (7)−0.0264 (7)0.0010 (6)−0.0042 (6)
C50.0506 (10)0.0498 (9)0.0401 (9)−0.0181 (8)−0.0011 (7)−0.0127 (7)
C60.0584 (11)0.0412 (8)0.0431 (9)−0.0182 (8)−0.0011 (8)−0.0079 (7)
C70.0554 (10)0.0546 (9)0.0341 (8)−0.0233 (8)0.0028 (7)−0.0109 (7)
Geometric parameters (Å, º) top
O4—C41.2664 (17)N2—H80.8600
O2—C11.2109 (18)C2—C31.310 (2)
O1—C11.3084 (17)C2—C11.489 (2)
O1—H10.8200C2—H20.9300
O3—C41.2363 (17)C4—C31.497 (2)
N1—C51.317 (2)C3—H30.9300
N1—C71.356 (2)C5—H50.9300
N1—H90.8600C6—C71.339 (2)
N2—C51.307 (2)C6—H60.9300
N2—C61.368 (2)C7—H70.9300
C1—O1—H1109.5O2—C1—C2121.36 (13)
C5—N1—C7109.00 (14)O1—C1—C2114.43 (12)
C5—N1—H9125.5C2—C3—C4124.42 (14)
C7—N1—H9125.5C2—C3—H3117.8
C5—N2—C6108.60 (13)C4—C3—H3117.8
C5—N2—H8125.7N2—C5—N1108.58 (15)
C6—N2—H8125.7N2—C5—H5125.7
C3—C2—C1124.31 (14)N1—C5—H5125.7
C3—C2—H2117.8C7—C6—N2107.01 (15)
C1—C2—H2117.8C7—C6—H6126.5
O3—C4—O4124.23 (14)N2—C6—H6126.5
O3—C4—C3117.70 (13)C6—C7—N1106.81 (15)
O4—C4—C3118.06 (12)C6—C7—H7126.6
O2—C1—O1124.20 (13)N1—C7—H7126.6
C3—C2—C1—O2178.47 (16)C6—N2—C5—N1−0.09 (19)
C3—C2—C1—O1−1.1 (2)C7—N1—C5—N2−0.12 (19)
C1—C2—C3—C4179.96 (13)C5—N2—C6—C70.27 (19)
O3—C4—C3—C2−179.96 (16)N2—C6—C7—N1−0.33 (19)
O4—C4—C3—C2−0.5 (2)C5—N1—C7—C60.3 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O4i0.821.752.5699 (16)173
N2—H8···O3ii0.861.822.6600 (18)166
N1—H9···O4iii0.861.942.7969 (16)172
Symmetry codes: (i) x+1, y, z; (ii) −x+1, −y+1, −z; (iii) −x+1, −y, −z+1.

Experimental details

Crystal data
Chemical formulaC3H5N2+·C4H3O4−
Mr184.15
Crystal system, space groupTriclinic, P1
Temperature (K)294
a, b, c (Å)7.4794 (4), 7.7522 (3), 8.4231 (4)
α, β, γ (°)69.695 (3), 81.415 (2), 66.193 (2)
V (Å3)419.04 (3)
Z2
Radiation typeMo Kα
µ (mm−1)0.12
Crystal size (mm)0.12 × 0.02 × 0.02
Data collection
DiffractometerNonius KappaCCD
Absorption correction–
No. of measured, independent and
observed [I > 2σ(I)] reflections		7824, 1922, 1443
Rint0.087
(sin θ/λ)max (Å−1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.051, 0.149, 1.07
No. of reflections1922
No. of parameters118
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å−3)0.31, −0.29

Computer programs: COLLECT (Nonius, 2000), DENZO and SCALEPACK (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2006), PARST95 (Nardelli, 1995).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O4i0.821.752.5699 (16)173.2
N2—H8···O3ii0.861.822.6600 (18)166.1
N1—H9···O4iii0.861.942.7969 (16)171.7
Symmetry codes: (i) x+1, y, z; (ii) −x+1, −y+1, −z; (iii) −x+1, −y, −z+1.
 

Acknowledgements

RMF is grateful to the Spanish Research Council (CSIC) for the use of a free-of-charge licence to the Cambridge Structural Database (Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]). RMF also thanks the Universidad del Valle, Colombia, and Instituto de Física de São Carlos, Brazil, for partial financial support.

References

First citationAllen, F. H. (2002). Acta Cryst. B58, 380–388.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
 First citationBednowitz, A. L. & Post, B. (1966). Acta Cryst. 21, 566–571.  CSD CrossRef IUCr Journals Web of Science Google Scholar
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 First citationFarrugia, L. J. (1997). J. Appl. Cryst. 30, 565.  CrossRef IUCr Journals Google Scholar
 First citationMacrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor, R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453–457.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
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Volume 65| Part 11| November 2009| Page o2717
https://doi.org/10.1107/S1600536809040793
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