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A co-crystal of ethyl­enedi­ammonium bis­­(3,5-di­nitro­benzoate) and 3,5-di­nitro­benzoic acid

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aColloids, Crystals and Interfaces Group, School of Chemical Engineering and Analytical Sciences, The University of Manchester, PO Box 88, Manchester M60 1QD, England
*Correspondence e-mail: h.jones-2@postgrad.manchester.ac.uk

(Received 6 April 2005; accepted 13 May 2005; online 21 May 2005)

The co-crystal of ethyl­enediammonium bis­(3,5-dinitro­benzoate) and 3,5-dinitro­benzoic acid, namely ethyl­enediaminium–3,5-dinitro­benzoate–3,5-dinitro­benzoic acid (1/2/2), C2H10N22+·2C7H3N2O6·2C7H4N2O6, has as the asymmetric unit one 3,5-dinitro­benzoic acid mol­ecule, one 3,5-dinitro­benzoate ion and one-half of the ethyl­enediammonium ion, as this cation lies on an inversion centre. Each ethyl­enediammonium ion is hydrogen bonded to four benzoate ions and two benzoic acid mol­ecules.

Comment

During experiments to measure the solubility of the monoclinic form of ethyl­enediammonium bis­(3,5-dinitro­benzoate), cocrystals, (I)[link], of this salt with 3,5-dinitro­benzoic acid were obtained.

[Scheme 1]

To measure the solubility of ethyl­enediammonium bis­(3,5-dinitro­benzoate) as a function of pH at 323 K, a suspension of the salt in water was prepared and allowed to equilibrate (Jones et al., 2005[Jones, H. P., Davey, R. J. & Cox, B. G. (2005). J. Phys. Chem. B, 109, 5273-5278.]). In one experiment, the pH was found to be unusually low for a slurry of this salt and the experiment was stopped, but the sample continued to be held at 323 K. The cocrystals grew as pale-yellow prisms and were recovered on filtration of the slurry. Formation of these cocrystals was not observed in other solubility measurements at higher pH. Protonated 3,5-dinitro­benzoic acid is only expected to be present below pH 5 at 323 K (de Levie et al., 1999[Levie, R. de (1999). Aqueous Acid-Base Equilibria and Titrations. New York: Oxford University Press.]).

In the crystal structure, both a protonated and a deproton­ated 3,5-dinitro­benzoic acid mol­ecule are present in the asymmetric unit. The ethyl­enediammonium ion lies on an inversion centre so that only one-half of the ion is in the asymmetric unit. Fig. 1[link] shows the structure and atom labelling.

Each ethyl­enediammonium ion is hydrogen bonded to four benzoate ions and two benzoic acid mol­ecules (Fig. 2[link]). The crystal structure contains hydrogen-bonded chains of ethyl­enediammonium and benzoate ions along the a axis in the motif C22(6) (Fig. 3[link]), hydrogen-bonded dimers of benzoate ions with benzoic acid mol­ecules with an O—H⋯O hydrogen bond through atom H7 in the motif D11(2), and dimers of ethyl­enediammonium ions hydrogen bonded to the carbon­yl group of a benzoic acid mol­ecule in the motif D11(2). The benzoate ions in this structure all lie in one plane and the benzoic acid mol­ecules all lie in another orientation.

[Figure 1]
Figure 1
View of the asymmetric unit of (I)[link], including the whole ethyl­enediaminium ion, which is on an inversion centre. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry code: (i) −x, −y, −z.]
[Figure 2]
Figure 2
Hydrogen bonding (dashed lines) between the ethyl­enediaminium and 3,5-dinitro­benzoate ions and the 3,5-dinitro­benzoic acid mol­ecules.
[Figure 3]
Figure 3
Unit cell contents, viewed along the c axis, showing hydrogen-bonded chains (dashed lines) along the a axis.

Experimental

Monoclinic ethyl­enediaminium bis­(3,5-dinitro­benzoate) was prepared by precipitation from a mixture of solutions of ethyl­enediamine (0.0145 mol) and 3,5-dinitro­benzoic acid (0.029 mol; supplied by Sigma–Aldrich, 99%) in ethanol (50 ml). An excess of monoclinic ethyl­enediammonium bis­(3,5-dinitro­benzoate) (0.0145 mol) was suspended in water (40 ml) at 323 K with stirring. The solution pH was recorded as 3.79. After 20 h, stirring was stopped and the suspension was held at 323 K for 5 d. The suspension was filtered and pale-yellow prisms were observed in the powder of the monoclinic ethyl­enediammonium bis­(3,5-dinitro­benzoate).

Crystal data
  • C2H10N22+·2C7H3N2O6- ·2C7H4N2O6

  • Mr = 908.6

  • Triclinic, [P \overline 1]

  • a = 7.0452 (3) Å

  • b = 11.2345 (4) Å

  • c = 11.7627 (5) Å

  • α = 91.838 (2)°

  • β = 96.230 (2)°

  • γ = 98.710 (1)°

  • V = 913.72 (6) Å3

  • Z = 1

  • Dx = 1.651 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 5294 reflections

  • θ = 1.0–25.0°

  • μ = 0.15 mm−1

  • T = 293 (2) K

  • Prism, pale yellow

  • 0.3 × 0.2 × 0.1 mm

Data collection
  • Nonius KappaCCD diffractometer

  • Thick-slice φ and ω scans to fill asymmetric unit

  • Absorption correction: multi-scan(Blessing, 1995[Blessing, R. H. (1995). Acta Cryst. A51, 33-38.])Tmin = 0.916, Tmax = 0.986

  • 8852 measured reflections

  • 3241 independent reflections

  • 2256 reflections with I > 2σ(I)

  • Rint = 0.046

  • θmax = 25.2°

  • h = −8 → 8

  • k = −13 → 13

  • l = −14 → 12

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.046

  • wR(F2) = 0.136

  • S = 1.01

  • 3241 reflections

  • 294 parameters

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

  • w = 1/[σ2(Fo2) + (0.0776P)2] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 0.20 e Å−3

  • Δρmin = −0.21 e Å−3

  • Extinction correction: SHELXL97

  • Extinction coefficient: 0.016 (4)

Table 1
Hydrogen-bond geometry (Å, °)[link]

D—H⋯A D—H H⋯A DA D—H⋯A
O7—H7⋯O1 0.83 (1) 1.68 (1) 2.507 (2) 173 (4)
N5—H5A⋯O2 0.89 1.88 2.732 (3) 161
N5—H5B⋯O8ii 0.89 2.17 2.820 (3) 129
N5—H5C⋯O1ii 0.89 2.02 2.899 (3) 170
Symmetry code: (ii) x+1, y, z.

All H atoms attached to C and N atoms were fixed using a riding model, with C—H distances 0.93 Å (CArH) and 0.97 Å (CH2), and N—H distances 0.89 Å. The Uiso(H) values were set equal to 1.2Ueq of the carrier atom for these H atoms. The hydr­oxy H atom was located in a Fourier difference map and the coordinates were refined with the O—H bond distance restrained to 0.82 (1) Å.

Data collection: COLLECT (Nonius, 2000[Nonius (2000). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: HKL 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: HKL 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, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]); software used to prepare material for publication: WinGX (Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]).

Supporting information


Computing details top

Data collection: Collect (Nonius, 2000); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

ethylenediaminium–3,5-dinitrobenzoate–3,5-dinitrobenzoic acid (1/2/2), C2H10N22+·2C7H3N2O6-·2C7H4N2O6 top
Crystal data top
0.5C2H10N22+·C7H3N2O6·C7H4N2O6Z = 2
Mr = 454.3F(000) = 466
Triclinic, P1Dx = 1.651 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 7.0452 (3) ÅCell parameters from 5294 reflections
b = 11.2345 (4) Åθ = 1.0–25.0°
c = 11.7627 (5) ŵ = 0.15 mm1
α = 91.838 (2)°T = 293 K
β = 96.230 (2)°Prism, pale yellow
γ = 98.710 (1)°0.3 × 0.2 × 0.1 mm
V = 913.72 (6) Å3
Data collection top
Nonius KappaCCD
diffractometer
3241 independent reflections
Radiation source: Enraf–Nonius FR5902256 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.046
φ or ω scans?θmax = 25.2°, θmin = 2.5°
Absorption correction: multi-scan
(Blessing, 1995)
h = 88
Tmin = 0.916, Tmax = 0.986k = 1313
8852 measured reflectionsl = 1412
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.046H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.136 w = 1/[σ2(Fo2) + (0.0776P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
3241 reflectionsΔρmax = 0.20 e Å3
294 parametersΔρmin = 0.21 e Å3
1 restraintExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.016 (4)
Special details top

Experimental. Solution pH was measured using an Accumet Basic AB15 pH meter with an Accumet glass calomel pH electrode and an ATC probe to compensate for temperature changes.

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
O10.3739 (2)0.04198 (13)0.75723 (14)0.0508 (4)
O20.6632 (3)0.01493 (13)0.76044 (15)0.0553 (5)
O30.7755 (3)0.38263 (14)0.94862 (14)0.0596 (5)
O40.6306 (3)0.42815 (15)1.09778 (14)0.0648 (5)
O50.0621 (3)0.26099 (18)1.15926 (16)0.0718 (6)
O60.0276 (3)0.12294 (18)1.05344 (18)0.0724 (6)
O70.5246 (3)0.24130 (15)0.69250 (16)0.0590 (5)
O80.2299 (3)0.26663 (15)0.62078 (17)0.0680 (5)
O90.1253 (3)0.66997 (17)0.50938 (18)0.0741 (6)
O100.3350 (3)0.82267 (16)0.5700 (2)0.0889 (7)
O110.9653 (3)0.76827 (14)0.73491 (15)0.0618 (5)
O121.0348 (3)0.58912 (16)0.75615 (16)0.0638 (5)
N10.6524 (3)0.37047 (16)1.01241 (16)0.0475 (5)
N20.0813 (3)0.19415 (18)1.07990 (18)0.0520 (5)
N30.2801 (3)0.71433 (18)0.55839 (17)0.0537 (5)
N40.9221 (3)0.65764 (17)0.72899 (16)0.0455 (5)
N50.9846 (3)0.05043 (17)0.65242 (17)0.0571 (6)
H5A0.89950.02650.70090.069*
H5B0.98630.12850.64130.069*
H5C1.10160.03820.68160.069*
C10.4465 (3)0.11491 (17)0.87777 (17)0.0371 (5)
C20.5689 (3)0.19825 (17)0.90467 (17)0.0394 (5)
H20.6810.19750.86940.047*
C30.5229 (3)0.28228 (18)0.98423 (17)0.0403 (5)
C40.3618 (3)0.28528 (19)1.04054 (18)0.0433 (6)
H40.3320.34271.09370.052*
C50.2463 (3)0.19926 (18)1.01452 (17)0.0400 (5)
C60.2833 (3)0.11494 (18)0.93258 (18)0.0395 (5)
H60.19980.05980.91510.047*
C70.5006 (3)0.02253 (17)0.79096 (18)0.0403 (5)
C80.4724 (3)0.43735 (17)0.65036 (16)0.0368 (5)
C90.3459 (3)0.51274 (18)0.60851 (17)0.0391 (5)
H90.21790.4820.58240.047*
C100.4134 (3)0.63433 (18)0.60626 (17)0.0404 (5)
C110.5990 (3)0.68435 (18)0.64562 (17)0.0400 (5)
H110.64050.76690.64520.048*
C120.7218 (3)0.60689 (18)0.68589 (17)0.0375 (5)
C130.6631 (3)0.48361 (18)0.68852 (17)0.0382 (5)
H130.74960.43320.71520.046*
C140.3964 (4)0.30531 (19)0.65396 (18)0.0432 (6)
C150.9287 (3)0.01948 (18)0.54167 (18)0.0421 (5)
H15A0.80060.0070.51020.051*
H15B0.92490.10480.55380.051*
H70.469 (5)0.1743 (18)0.709 (3)0.123 (14)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0486 (11)0.0417 (8)0.0650 (10)0.0101 (8)0.0127 (8)0.0141 (7)
O20.0492 (11)0.0509 (9)0.0700 (11)0.0061 (8)0.0237 (9)0.0159 (8)
O30.0678 (13)0.0629 (11)0.0573 (11)0.0291 (9)0.0207 (10)0.0089 (8)
O40.0793 (14)0.0686 (11)0.0535 (11)0.0243 (10)0.0148 (9)0.0255 (8)
O50.0613 (13)0.0999 (14)0.0587 (12)0.0094 (10)0.0249 (10)0.0247 (10)
O60.0568 (13)0.0806 (13)0.0898 (15)0.0248 (10)0.0301 (11)0.0154 (10)
O70.0558 (12)0.0416 (9)0.0771 (12)0.0025 (8)0.0011 (9)0.0145 (8)
O80.0566 (13)0.0474 (9)0.0902 (14)0.0091 (9)0.0146 (10)0.0145 (8)
O90.0581 (13)0.0767 (13)0.0840 (14)0.0186 (10)0.0189 (11)0.0052 (10)
O100.0967 (18)0.0460 (12)0.1208 (19)0.0235 (11)0.0197 (14)0.0052 (10)
O110.0587 (12)0.0467 (10)0.0724 (12)0.0097 (8)0.0015 (9)0.0027 (8)
O120.0422 (11)0.0674 (11)0.0818 (13)0.0111 (9)0.0032 (9)0.0066 (9)
N10.0557 (14)0.0459 (11)0.0427 (11)0.0130 (9)0.0059 (10)0.0060 (8)
N20.0418 (13)0.0608 (13)0.0524 (13)0.0015 (10)0.0105 (10)0.0023 (10)
N30.0579 (15)0.0534 (13)0.0521 (12)0.0192 (11)0.0023 (11)0.0025 (9)
N40.0413 (12)0.0497 (12)0.0449 (11)0.0020 (10)0.0083 (9)0.0036 (8)
N50.0560 (14)0.0594 (12)0.0518 (12)0.0124 (10)0.0190 (10)0.0014 (9)
C10.0410 (13)0.0337 (10)0.0355 (11)0.0020 (9)0.0051 (9)0.0013 (8)
C20.0416 (14)0.0407 (11)0.0364 (12)0.0055 (10)0.0084 (10)0.0011 (9)
C30.0445 (14)0.0409 (11)0.0361 (12)0.0086 (10)0.0046 (10)0.0020 (9)
C40.0466 (15)0.0454 (12)0.0368 (12)0.0013 (10)0.0072 (10)0.0036 (9)
C50.0350 (13)0.0474 (12)0.0369 (12)0.0012 (10)0.0093 (10)0.0024 (9)
C60.0379 (13)0.0394 (11)0.0407 (12)0.0051 (9)0.0040 (10)0.0014 (8)
C70.0431 (15)0.0329 (11)0.0438 (13)0.0003 (10)0.0092 (11)0.0014 (9)
C80.0415 (14)0.0384 (11)0.0298 (11)0.0020 (9)0.0066 (9)0.0032 (8)
C90.0379 (13)0.0452 (12)0.0328 (11)0.0020 (10)0.0041 (9)0.0004 (8)
C100.0472 (14)0.0430 (12)0.0327 (11)0.0117 (10)0.0055 (10)0.0020 (8)
C110.0482 (15)0.0356 (11)0.0361 (12)0.0048 (10)0.0069 (10)0.0015 (8)
C120.0387 (13)0.0415 (11)0.0316 (11)0.0011 (9)0.0077 (9)0.0020 (8)
C130.0444 (14)0.0393 (11)0.0320 (11)0.0069 (10)0.0075 (10)0.0039 (8)
C140.0467 (16)0.0424 (12)0.0385 (12)0.0002 (11)0.0041 (11)0.0059 (9)
C150.0437 (14)0.0389 (11)0.0434 (12)0.0004 (10)0.0103 (10)0.0060 (9)
Geometric parameters (Å, º) top
O1—C71.271 (3)C1—C21.388 (3)
O2—C71.229 (3)C1—C71.516 (3)
O3—N11.226 (2)C2—C31.379 (3)
O4—N11.224 (2)C2—H20.93
O5—N21.223 (3)C3—C41.371 (3)
O6—N21.215 (3)C4—C51.376 (3)
O7—C141.292 (3)C4—H40.93
O7—H70.833 (10)C5—C61.390 (3)
O8—C141.205 (3)C6—H60.93
O9—N31.204 (3)C8—C91.384 (3)
O10—N31.219 (3)C8—C131.386 (3)
O11—N41.232 (2)C8—C141.502 (3)
O12—N41.213 (2)C9—C101.379 (3)
N1—C31.468 (3)C9—H90.93
N2—C51.469 (3)C10—C111.367 (3)
N3—C101.477 (3)C11—C121.377 (3)
N4—C121.468 (3)C11—H110.93
N5—C151.483 (3)C12—C131.386 (3)
N5—H5A0.89C13—H130.93
N5—H5B0.89C15—C15i1.506 (4)
N5—H5C0.89C15—H15A0.97
C1—C61.377 (3)C15—H15B0.97
C14—O7—H7109 (3)C1—C6—C5118.5 (2)
O4—N1—O3123.8 (2)C1—C6—H6120.7
O4—N1—C3118.1 (2)C5—C6—H6120.7
O3—N1—C3118.10 (18)O2—C7—O1125.5 (2)
O6—N2—O5123.3 (2)O2—C7—C1117.6 (2)
O6—N2—C5118.5 (2)O1—C7—C1116.8 (2)
O5—N2—C5118.1 (2)C9—C8—C13120.38 (19)
O9—N3—O10123.6 (2)C9—C8—C14118.1 (2)
O9—N3—C10118.95 (19)C13—C8—C14121.48 (19)
O10—N3—C10117.5 (2)C10—C9—C8118.6 (2)
O12—N4—O11124.0 (2)C10—C9—H9120.7
O12—N4—C12118.64 (18)C8—C9—H9120.7
O11—N4—C12117.41 (19)C11—C10—C9123.0 (2)
C15—N5—H5A109.5C11—C10—N3118.33 (19)
C15—N5—H5B109.5C9—C10—N3118.7 (2)
H5A—N5—H5B109.5C10—C11—C12116.98 (19)
C15—N5—H5C109.5C10—C11—H11121.5
H5A—N5—H5C109.5C12—C11—H11121.5
H5B—N5—H5C109.5C11—C12—C13122.6 (2)
C6—C1—C2119.86 (19)C11—C12—N4118.40 (18)
C6—C1—C7121.5 (2)C13—C12—N4119.0 (2)
C2—C1—C7118.6 (2)C8—C13—C12118.3 (2)
C3—C2—C1119.4 (2)C8—C13—H13120.8
C3—C2—H2120.3C12—C13—H13120.8
C1—C2—H2120.3O8—C14—O7125.3 (2)
C4—C3—C2122.5 (2)O8—C14—C8120.6 (2)
C4—C3—N1118.23 (19)O7—C14—C8114.1 (2)
C2—C3—N1119.3 (2)N5—C15—C15i110.4 (2)
C3—C4—C5116.8 (2)N5—C15—H15A109.6
C3—C4—H4121.6C15i—C15—H15A109.6
C5—C4—H4121.6N5—C15—H15B109.6
C4—C5—C6122.9 (2)C15i—C15—H15B109.6
C4—C5—N2118.01 (19)H15A—C15—H15B108.1
C6—C5—N2119.0 (2)
Symmetry code: (i) x+2, y, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O7—H7···O10.83 (1)1.68 (1)2.507 (2)173 (4)
N5—H5A···O20.891.882.732 (3)161
N5—H5B···O8ii0.892.172.820 (3)129
N5—H5C···O1ii0.892.022.899 (3)170
Symmetry code: (ii) x+1, y, z.
 

Footnotes

Current address: Pharmaceutical R&D, Pfizer Global R&D (IPC 435), Ramsgate Road, Sandwich, Kent CT13 9NJ, England.

Acknowledgements

The authors thank Sanofi–Aventis Ltd for funding.

References

First citationBlessing, R. H. (1995). Acta Cryst. A51, 33–38.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationFarrugia, L. J. (1997). J. Appl. Cryst. 30, 565.  CrossRef IUCr Journals Google Scholar
First citationFarrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838.  CrossRef CAS IUCr Journals Google Scholar
First citationJones, H. P., Davey, R. J. & Cox, B. G. (2005). J. Phys. Chem. B, 109, 5273–5278.  Web of Science CSD CrossRef PubMed CAS Google Scholar
First citationLevie, R. de (1999). Aqueous Acid–Base Equilibria and Titrations. New York: Oxford University Press.  Google Scholar
First citationNonius (2000). COLLECT. Nonius BV, Delft, The Netherlands.  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 citationSheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.  Google Scholar

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