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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 70| Part 2| February 2014| Pages o186-o187
doi:10.1107/S1600536814001275

Cytosinium hydrogen selenite

Radhwane Takouachet,a Rim Benali-Cherifa and Nourredine Benali-Cherifa*

aLaboratoire des Structures, Propriétés et Interactions InterAtomiques, Université Abbes Laghrour-Khenchela, 40000 Khenchela, Algeria
*Correspondence e-mail: benalicherif@hotmail.com

(Received 14 January 2014; accepted 17 January 2014; online 22 January 2014)

In the crystal structure of the title salt, C4H6N3O+·HSeO3−, systematic name 6-amino-2-methyl­idene-2,3-di­hydro­pyrim­idin-1-ium hydrogen selenite, the hydrogenselenite anions and the cytosinium cations are linked via N—H⋯O, N—H⋯Se, O—H⋯O, O—H··Se and C—H⋯O hydrogen bonds, forming a three-dimensional framework.

CCDC reference: 982125

Related literature

For the crystal structure of cytosine, see: Barker & Marsh (1964[Barker, D. L. & Marsh, R. E. (1964). Acta Cryst. 17, 1581-1587.]), and of cytosine monohydrate, see: Jeffrey & Kinoshita (1963[Jeffrey, G. A. & Kinoshita, Y. (1963). Acta Cryst. 16, 20-28.]). For examples of some inorganic cytosinium salts, see: Mandel (1977[Mandel, N. S. (1977). Acta Cryst. B33, 1079-1082.]); Bagieu-Beucher (1990[Bagieu-Beucher, M. (1990). Acta Cryst. C46, 238-240.]). For examples of the structures of cytosinium salts of organic acids, see: Gdaniec et al. (1989[Gdaniec, M., Brycki, B. & Szafran, M. (1989). J. Mol. Struct. pp. 57-64.]); Smith et al. (2005[Smith, G., Wermuth, U. D. & Healy, P. C. (2005). Acta Cryst. E61, o746-o748.]). For examples of the structure of the hydrogenselenite anion, see: Richie & Harrison (2003[Ritchie, L. K. & Harrison, W. T. A. (2003). Acta Cryst. E59, o1296-o1298.]); Wang et al. (2006[Wang, J.-J., Tessier, C. & Holm, R. H. (2006). Inorg. Chem. 45, 2979-2988.]); Chomnilpan et al. (1981[Chomnilpan, S., Liminga, R., Sonneveld, E. J. & Visser, J. W. (1981). Acta Cryst. B37, 2217-2220.]).

[Scheme 1]

Experimental

Crystal data

  • C4H6N3O+·HSeO3−

  • Mr = 240.09

  • Orthorhombic, P c a 21

  • a = 7.0051 (3) Å

  • b = 8.6342 (2) Å

  • c = 12.7131 (3) Å

  • V = 768.93 (4) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 4.86 mm−1

  • T = 293 K

  • 0.20 × 0.15 × 0.10 mm
Data collection

  • Nonius KappaCCD diffractometer

  • Absorption correction: multi-scan (Blessing, 1995[Blessing, R. H. (1995). Acta Cryst. A51, 33-38.]) Tmin = 0.295, Tmax = 0.369

  • 4568 measured reflections

  • 1494 independent reflections

  • 1283 reflections with I > 2σ(I)

  • Rint = 0.067
Refinement

  • R[F2 > 2σ(F2)] = 0.042

  • wR(F2) = 0.098

  • S = 1.04

  • 1494 reflections

  • 125 parameters

  • 7 restraints

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

  • Δρmax = 0.46 e Å−3

  • Δρmin = −0.49 e Å−3

  • Absolute structure: Flack parameter determined using 518 quotients [(I+)−(I−)]/[(I+)+(I−)] (Parsons et al., 2013[Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249-259.])

  • Absolute structure parameter: −0.02 (3)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A D⋯A D—H⋯A
N1—H1A⋯Se1i 0.85 (3) 3.04 (6) 3.789 (9) 148 (9)
N1—H1A⋯O3i 0.85 (3) 1.93 (3) 2.785 (10) 176 (10)
N2—H2A⋯O4ii 0.86 (3) 1.97 (5) 2.798 (12) 160 (10)
N3—H3A⋯Se1iii 0.84 (3) 3.06 (3) 3.896 (12) 174 (7)
N3—H3A⋯O2iii 0.84 (3) 2.42 (7) 3.126 (12) 141 (8)
N3—H3A⋯O4iii 0.84 (3) 2.42 (4) 3.196 (17) 152 (8)
N3—H3B⋯O3ii 0.84 (3) 1.95 (4) 2.772 (12) 166 (12)
O2—H2⋯Se1iv 0.81 (3) 2.97 (6) 3.691 (7) 149 (10)
O2—H2⋯O4iv 0.81 (3) 1.87 (3) 2.682 (10) 180 (14)
C3—H3⋯O1v 0.93 2.46 3.168 (12) 133
C4—H4⋯O2vi 0.93 2.31 3.196 (11) 159
Symmetry codes: (i) [x+{\script{1\over 2}}, -y, z]; (ii) [x+{\script{1\over 2}}, -y+1, z]; (iii) [-x+1, -y+1, z+{\script{1\over 2}}]; (iv) [x-{\script{1\over 2}}, -y+1, z]; (v) [-x+{\script{3\over 2}}, y, z+{\script{1\over 2}}]; (vi) [-x+1, -y, z+{\script{1\over 2}}].

Data collection: COLLECT (Hooft, 1998[Hooft, R. W. W. (1998). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO and 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 and SCALEPACK; program(s) used to solve structure: SIR2004 (Burla et al., 2005[Burla, M. C., Caliandro, R., Camalli, M., Carrozzini, B., Cascarano, G. L., De Caro, L., Giacovazzo, C., Polidori, G. & Spagna, R. (2005). J. Appl. Cryst. 38, 381-388.]); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]); software used to prepare material for publication: SHELXL2013 and PLATON.

Supporting information

CCDC reference: 982125

Crystal structure: contains datablocks Global, I. DOI: 10.1107/S1600536814001275/su2689sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536814001275/su2689Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536814001275/su2689Isup3.cml

checkCIF report


Comment top

The crystal structure of cytosine (Barker & Marsh, 1964) and cytosine monohydrate (Jeffrey & Kinoshita, 1963) were determined many years ago. Many inorganic cytosinium salts have been synthesized, including the hydrochloride (Mandel, 1977) and the dihydrogenmonophosphate (Bagieu-Beucher, 1990) salts. Cytosinium salts of organic acids are also common, these include for example, cytosinium trichloroacetate (Gdaniec et al., 1989) and cytosinium 3,5-dinitrosalicylate (Smith et al., 2005). We report herein on the molecular structure of a new cytosinium salt formed by the reaction of cytosine with selenious acid.

The structure of the title salt is illustrated in Fig. 1. The HSeO3- ion is pyramidal with two short Se—O bonds, Se1—O3 = 1.634 (8) A° and Se1—O4 = 1.686 (6) A°, and a longer Se—OH bond, Se1—O2 = 1.738 (7) A°. These values are very similar to those described in the literature (Richie & Harrison, 2003; Wang et al., 2006; Chomnilpan et al., 1981). The geometry of this inorganic moiety clearly implies that one proton was transferred from selenious acid to cytosine.

In the crystal, the anions and cations are linked via N—H···O/Se, O-H···O/Se and C-H···O hydrogen bonds forming a three-dimensional framework (Table 1 and Fig. 2).

Related literature top

For the crystal structure of cytosine, see: Barker & Marsh (1964), and of cytosine monohydrate, see: Jeffrey & Kinoshita (1963). For examples of some inorganic cytosinium salts, see: Mandel (1977); Bagieu-Beucher (1990). For examples of the structures of cytosinium salts of organic acids, see: Gdaniec et al. (1989); Smith et al. (2005). For examples of the structure of the hydrogenselenite anion, see: Richie & Harrison (2003); Wang et al. (2006); Chomnilpan et al. (1981). SCHEME SHOWS SULFATE

Experimental top

Selenious acid (H2SeO3) was added to an aqueous solution of cytosine in the stoichiometric ratio 1:1, at room temperature. After four weeks colourless prismatic crystals of the title salt were obtained.

Refinement top

All the H atoms could be located in difference Fourier maps and this was confirmed by plotting difference Fourier maps using the ContourDif routine in PLATON (Spek, 2009). In the final cycles of refinement the NH2 distances were restrained to N-H = 0.86 (2) and H···H = 1.33 (2) Å with Uiso(H) = 1.2Ueq(N). The OH distance was restrained to O-H = 0.82 (2) Å with Uiso(H) = 1.5Ueq(O). The C bound H atoms were included in calculated positions and treated as riding atoms: C-H = 0.93 Å with Uiso(H) = 1.2Ueq(C).

Structure description top

The crystal structure of cytosine (Barker & Marsh, 1964) and cytosine monohydrate (Jeffrey & Kinoshita, 1963) were determined many years ago. Many inorganic cytosinium salts have been synthesized, including the hydrochloride (Mandel, 1977) and the dihydrogenmonophosphate (Bagieu-Beucher, 1990) salts. Cytosinium salts of organic acids are also common, these include for example, cytosinium trichloroacetate (Gdaniec et al., 1989) and cytosinium 3,5-dinitrosalicylate (Smith et al., 2005). We report herein on the molecular structure of a new cytosinium salt formed by the reaction of cytosine with selenious acid.

The structure of the title salt is illustrated in Fig. 1. The HSeO3- ion is pyramidal with two short Se—O bonds, Se1—O3 = 1.634 (8) A° and Se1—O4 = 1.686 (6) A°, and a longer Se—OH bond, Se1—O2 = 1.738 (7) A°. These values are very similar to those described in the literature (Richie & Harrison, 2003; Wang et al., 2006; Chomnilpan et al., 1981). The geometry of this inorganic moiety clearly implies that one proton was transferred from selenious acid to cytosine.

In the crystal, the anions and cations are linked via N—H···O/Se, O-H···O/Se and C-H···O hydrogen bonds forming a three-dimensional framework (Table 1 and Fig. 2).

For the crystal structure of cytosine, see: Barker & Marsh (1964), and of cytosine monohydrate, see: Jeffrey & Kinoshita (1963). For examples of some inorganic cytosinium salts, see: Mandel (1977); Bagieu-Beucher (1990). For examples of the structures of cytosinium salts of organic acids, see: Gdaniec et al. (1989); Smith et al. (2005). For examples of the structure of the hydrogenselenite anion, see: Richie & Harrison (2003); Wang et al. (2006); Chomnilpan et al. (1981). SCHEME SHOWS SULFATE

Computing details top

Data collection: COLLECT (Hooft, 1998); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL2013 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. A view of the molecular structure of the title salt, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. A view along the b axis of the crystal packing of the title compound. The hydrogen-bonds are shown as dashed lines (See Table 1 for details).
6-Amino-2-methylidene-2,3-dihydropyrimidin-1-ium hydrogen selenite top
Crystal data top
C4H6N3O+·HSeO3−Dx = 2.074 Mg m−3
Mr = 240.09Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pca21Cell parameters from 5415 reflections
a = 7.0051 (3) Åθ = 3.8–29.5°
b = 8.6342 (2) ŵ = 4.86 mm−1
c = 12.7131 (3) ÅT = 293 K
V = 768.93 (4) Å3Prism, colourless
Z = 40.20 × 0.15 × 0.10 mm
F(000) = 472
Data collection top
Nonius KappaCCD
diffractometer		1494 independent reflections
Radiation source: fine-focus sealed tube1283 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.067
ω – θ scansθmax = 26.0°, θmin = 3.8°
Absorption correction: multi-scan
(Blessing, 1995)		h = −8→8
Tmin = 0.295, Tmax = 0.369k = −10→10
4568 measured reflectionsl = −14→15
Refinement top
Refinement on F2Hydrogen site location: difference Fourier map
Least-squares matrix: fullH atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.042 w = 1/[σ2(Fo2) + (0.0404P)2 + 0.8215P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.098(Δ/σ)max < 0.001
S = 1.04Δρmax = 0.46 e Å−3
1494 reflectionsΔρmin = −0.49 e Å−3
125 parametersExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
7 restraintsExtinction coefficient: 0.018 (4)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack parameter determined using 518 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Secondary atom site location: difference Fourier mapAbsolute structure parameter: −0.02 (3)
Crystal data top
C4H6N3O+·HSeO3−V = 768.93 (4) Å3
Mr = 240.09Z = 4
Orthorhombic, Pca21Mo Kα radiation
a = 7.0051 (3) ŵ = 4.86 mm−1
b = 8.6342 (2) ÅT = 293 K
c = 12.7131 (3) Å0.20 × 0.15 × 0.10 mm
Data collection top
Nonius KappaCCD
diffractometer		1494 independent reflections
Absorption correction: multi-scan
(Blessing, 1995)		1283 reflections with I > 2σ(I)
Tmin = 0.295, Tmax = 0.369Rint = 0.067
4568 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.042H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.098Δρmax = 0.46 e Å−3
S = 1.04Δρmin = −0.49 e Å−3
1494 reflectionsAbsolute structure: Flack parameter determined using 518 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
125 parametersAbsolute structure parameter: −0.02 (3)
7 restraints
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.9370 (10)0.0316 (8)0.0502 (5)0.050 (2)
N10.8269 (12)−0.0384 (8)0.2127 (7)0.0392 (19)
H1A0.832 (17)−0.134 (5)0.194 (8)0.047*
N20.8534 (12)0.2200 (8)0.1669 (6)0.0363 (17)
H2A0.885 (14)0.300 (8)0.130 (7)0.044*
N30.7775 (19)0.4148 (8)0.2818 (10)0.047 (3)
H3A0.732 (17)0.455 (9)0.337 (5)0.056*
H3B0.817 (16)0.489 (8)0.245 (6)0.056*
C10.8779 (14)0.0666 (10)0.1365 (8)0.037 (2)
C20.7901 (14)0.2661 (10)0.2619 (8)0.036 (2)
C30.7485 (14)0.1527 (10)0.3383 (8)0.041 (2)
H30.70880.17990.40560.049*
C40.7686 (17)0.0029 (10)0.3095 (8)0.041 (2)
H40.7413−0.07420.35830.049*
Se10.43127 (11)0.36795 (7)0.02452 (11)0.0378 (4)
O20.2460 (11)0.3114 (7)−0.0579 (6)0.0444 (16)
H20.147 (10)0.350 (12)−0.038 (10)0.067*
O30.3461 (15)0.3439 (7)0.1431 (6)0.054 (2)
O40.4180 (9)0.5615 (6)0.0084 (8)0.0432 (19)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.063 (4)0.039 (3)0.048 (6)0.004 (3)0.007 (3)−0.006 (3)
N10.051 (5)0.022 (3)0.045 (5)0.001 (3)−0.005 (4)0.003 (3)
N20.051 (4)0.023 (4)0.035 (4)0.000 (3)−0.001 (3)0.004 (3)
N30.062 (8)0.029 (3)0.049 (5)0.002 (5)0.004 (5)−0.004 (4)
C10.038 (5)0.024 (4)0.047 (6)−0.001 (4)−0.004 (4)−0.004 (4)
C20.043 (7)0.030 (4)0.035 (6)0.004 (4)−0.002 (5)−0.001 (4)
C30.050 (6)0.036 (5)0.036 (5)−0.004 (4)0.000 (4)−0.002 (4)
C40.045 (6)0.035 (5)0.042 (6)−0.003 (4)−0.003 (5)0.009 (4)
Se10.0425 (5)0.0233 (4)0.0475 (5)0.0031 (3)−0.0018 (7)−0.0008 (7)
O20.046 (4)0.035 (3)0.053 (4)0.002 (3)−0.002 (3)−0.009 (3)
O30.098 (6)0.022 (3)0.041 (4)0.005 (3)−0.001 (4)0.002 (3)
O40.052 (3)0.023 (3)0.055 (5)−0.001 (2)0.003 (4)−0.001 (3)
Geometric parameters (Å, º) top
O1—C11.211 (11)N3—H3B0.84 (3)
N1—C41.345 (14)C2—C31.409 (13)
N1—C11.374 (13)C3—C41.352 (12)
N1—H1A0.85 (3)C3—H30.9300
N2—C21.346 (11)C4—H40.9300
N2—C11.391 (11)Se1—O31.634 (8)
N2—H2A0.86 (3)Se1—O41.686 (6)
N3—C21.312 (12)Se1—O21.738 (7)
N3—H3A0.84 (3)O2—H20.81 (3)
C4—N1—C1123.3 (7)N3—C2—C3122.2 (10)
C4—N1—H1A121 (7)N2—C2—C3118.7 (8)
C1—N1—H1A115 (7)C4—C3—C2117.2 (9)
C2—N2—C1124.9 (8)C4—C3—H3121.4
C2—N2—H2A110 (7)C2—C3—H3121.4
C1—N2—H2A125 (7)N1—C4—C3122.2 (8)
C2—N3—H3A126 (6)N1—C4—H4118.9
C2—N3—H3B128 (6)C3—C4—H4118.9
H3A—N3—H3B106 (5)O3—Se1—O4102.6 (4)
O1—C1—N1124.3 (9)O3—Se1—O2104.3 (5)
O1—C1—N2122.1 (9)O4—Se1—O299.4 (4)
N1—C1—N2113.6 (8)Se1—O2—H2110 (9)
N3—C2—N2119.0 (9)
C4—N1—C1—O1177.3 (10)C1—N2—C2—C31.5 (15)
C4—N1—C1—N2−3.4 (14)N3—C2—C3—C4−179.2 (12)
C2—N2—C1—O1−179.4 (10)N2—C2—C3—C4−2.4 (15)
C2—N2—C1—N11.3 (13)C1—N1—C4—C32.7 (17)
C1—N2—C2—N3178.4 (10)C2—C3—C4—N10.4 (16)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···Se1i0.85 (3)3.04 (6)3.789 (9)148 (9)
N1—H1A···O3i0.85 (3)1.93 (3)2.785 (10)176 (10)
N2—H2A···O4ii0.86 (3)1.97 (5)2.798 (12)160 (10)
N3—H3A···Se1iii0.84 (3)3.06 (3)3.896 (12)174 (7)
N3—H3A···O2iii0.84 (3)2.42 (7)3.126 (12)141 (8)
N3—H3A···O4iii0.84 (3)2.42 (4)3.196 (17)152 (8)
N3—H3B···O3ii0.84 (3)1.95 (4)2.772 (12)166 (12)
O2—H2···Se1iv0.81 (3)2.97 (6)3.691 (7)149 (10)
O2—H2···O4iv0.81 (3)1.87 (3)2.682 (10)180 (14)
C3—H3···O1v0.932.463.168 (12)133
C4—H4···O2vi0.932.313.196 (11)159
Symmetry codes: (i) x+1/2, −y, z; (ii) x+1/2, −y+1, z; (iii) −x+1, −y+1, z+1/2; (iv) x−1/2, −y+1, z; (v) −x+3/2, y, z+1/2; (vi) −x+1, −y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···Se1i0.85 (3)3.04 (6)3.789 (9)148 (9)
N1—H1A···O3i0.85 (3)1.93 (3)2.785 (10)176 (10)
N2—H2A···O4ii0.86 (3)1.97 (5)2.798 (12)160 (10)
N3—H3A···Se1iii0.84 (3)3.06 (3)3.896 (12)174 (7)
N3—H3A···O2iii0.84 (3)2.42 (7)3.126 (12)141 (8)
N3—H3A···O4iii0.84 (3)2.42 (4)3.196 (17)152 (8)
N3—H3B···O3ii0.84 (3)1.95 (4)2.772 (12)166 (12)
O2—H2···Se1iv0.81 (3)2.97 (6)3.691 (7)149 (10)
O2—H2···O4iv0.81 (3)1.87 (3)2.682 (10)180 (14)
C3—H3···O1v0.932.463.168 (12)133
C4—H4···O2vi0.932.313.196 (11)159
Symmetry codes: (i) x+1/2, −y, z; (ii) x+1/2, −y+1, z; (iii) −x+1, −y+1, z+1/2; (iv) x−1/2, −y+1, z; (v) −x+3/2, y, z+1/2; (vi) −x+1, −y, z+1/2.
 

Acknowledgements

We are grateful to Dr M. Giorgi, Faculté des Sciences et Techniques de Saint Jeŕome, Marseille, France, for providing access to the X-ray diffraction facilities. We also thank Abbes Laghrour Khenchela University, le Ministére de l'Enseignement Supérieur et de la Recherche Scientifique–Algeria and the Direction Générale de la Recherche Scientifique et du Développement Technologique–Algeria for financial support.

References

First citationBagieu-Beucher, M. (1990). Acta Cryst. C46, 238–240.  CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
 First citationBarker, D. L. & Marsh, R. E. (1964). Acta Cryst. 17, 1581–1587.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
 First citationBlessing, R. H. (1995). Acta Cryst. A51, 33–38.  CrossRef CAS Web of Science IUCr Journals Google Scholar
 First citationBurla, M. C., Caliandro, R., Camalli, M., Carrozzini, B., Cascarano, G. L., De Caro, L., Giacovazzo, C., Polidori, G. & Spagna, R. (2005). J. Appl. Cryst. 38, 381–388.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationChomnilpan, S., Liminga, R., Sonneveld, E. J. & Visser, J. W. (1981). Acta Cryst. B37, 2217–2220.  CrossRef CAS IUCr Journals Google Scholar
 First citationGdaniec, M., Brycki, B. & Szafran, M. (1989). J. Mol. Struct. pp. 57–64.  CSD CrossRef Web of Science Google Scholar
 First citationHooft, R. W. W. (1998). COLLECT. Nonius BV, Delft, The Netherlands.  Google Scholar
 First citationJeffrey, G. A. & Kinoshita, Y. (1963). Acta Cryst. 16, 20–28.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
 First citationMandel, N. S. (1977). Acta Cryst. B33, 1079–1082.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
 First citationOtwinowski, 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.  Google Scholar
 First citationParsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249–259.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationRitchie, L. K. & Harrison, W. T. A. (2003). Acta Cryst. E59, o1296–o1298.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
 First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationSmith, G., Wermuth, U. D. & Healy, P. C. (2005). Acta Cryst. E61, o746–o748.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
 First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationWang, J.-J., Tessier, C. & Holm, R. H. (2006). Inorg. Chem. 45, 2979–2988.  Web of Science CSD CrossRef PubMed CAS Google Scholar

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ISSN: 2056-9890
Volume 70| Part 2| February 2014| Pages o186-o187
doi:10.1107/S1600536814001275
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