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ISSN: 2056-9890

Tri­ethyl­ammonium (2R,3R)-2,3-bis­­(benzo­yl­oxy)-3-carb­­oxy­propano­ate

aKey Laboratory of Functional Inorganic Material Chemistry (HLJU), Ministry of Education, and School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, People's Republic of China
*Correspondence e-mail: gmli_2000@163.com

(Received 22 December 2011; accepted 1 February 2012; online 10 February 2012)

In the anion of the title salt, C6H16N+·C18H13O8, one of the carboxyl groups is deprotonated. Its O atoms are involved in inter­molecular hydrogen bonding with the carboxyl group of an adjacent anion and the amino group of an adjacent cation. The two benzoyloxy rings are oriented with respect to each other at a dihedral angle of 79.46 (6)°.

Related literature

For background to tartaric acid derivatives, see: Kassai et al. (2000[Kassai, C., Juvancz, Z., BaAlint, J., Fogassy, E. & Kozma, D. (2000). Tetrahedron, 56, 8355-8359.]); Tan et al. (2006[Tan, B., Luo, G.-S., Qi, X. & Wang, J.-D. (2006). Sep. Purif. Technol. A, 49, 186-191.]).

[Scheme 1]

Experimental

Crystal data
  • C6H16N+·C18H13O8

  • Mr = 459.48

  • Orthorhombic, P 21 21 21

  • a = 11.2148 (12) Å

  • b = 12.9835 (13) Å

  • c = 15.9499 (17) Å

  • V = 2322.4 (4) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.10 mm−1

  • T = 293 K

  • 0.20 × 0.20 × 0.18 mm

Data collection
  • Rigaku R-AXIS RAPID diffractometer

  • 17272 measured reflections

  • 3242 independent reflections

  • 2336 reflections with I > 2σ(I)

  • Rint = 0.067

Refinement
  • R[F2 > 2σ(F2)] = 0.042

  • wR(F2) = 0.095

  • S = 1.02

  • 3242 reflections

  • 309 parameters

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

  • Δρmax = 0.20 e Å−3

  • Δρmin = −0.21 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H101⋯O4i 0.95 (3) 1.82 (3) 2.770 (3) 177 (3)
O5—H51⋯O3ii 0.93 (4) 1.60 (3) 2.525 (2) 171 (3)
Symmetry codes: (i) x-1, y, z; (ii) [-x+2, y+{\script{1\over 2}}, -z+{\script{3\over 2}}].

Data collection: RAPID-AUTO (Rigaku, 1998[Rigaku (1998). RAPID-AUTO. Rigaku Corporation, Tokyo, Japan.]); cell refinement: RAPID-AUTO; data reduction: CrystalClear (Rigaku/MSC, 2002[Rigaku/MSC (2002). CrystalClear. Rigaku/MSC Inc., The Woodlands, Texas, USA.]); program(s) used to solve structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

Optically active tartaric acid and its acyl derivatives (e.g. diacetyl, dibenzoyl, di-p-toluyl) continue to be widely used in the resolution of racemates. Their resolving power is connected with the ability to form diastereomeric salts with racemic amines and hydrazides. (2R,3R)-O,O'-Dibenzoyl-tartaric acid (DBTA) has been known as a chiral selector of enantiomers, such as ephedrine, chiral alcohols and N-methylamphetamine. It was also observed that DBTA can form complexes with some alcohols and aminos; the complex forming properties of DBTA have been investigated (Kassai et al., 2000; Tan et al., 2006).

The asymmertric unit of title compound contains one (2R,3R)-O,O'-dibenzoyl-tartrate anion and one triethylamine cation. In the anion, the two benzene rings make a dihedral angle of 79.46 (6)° (Fig. 1). In the crystal packing, intermoleculear O—H···O and N—H···O hydrogen bonds link these cations and anions into chain structures along [010] (Fig. 2, Table 1).

Related literature top

For background to tartaric acid derivatives, see: Kassai et al. (2000); Tan et al. (2006).

Experimental top

(2R,3R)-O,O'-Dibenzoyl-tartaric acid was a commercially available compound and used as received without further purification. (2R,3R)-O,O'-Dibenzoyl-tartaric acid (0.358 g, 1.0 mmol) and triethylamine (1 mL, 2 mol/L) were dissolved in methanol (8 mL), and the solution was stirring for 10 min at room temperature. And then, the solution was stood at room temperature for a few days, colorless block crystals of title compound were obtained (yield 27%).

Refinement top

O-bound and N-bound H atoms were located in a difference Fourier map and refined freely. H atoms bound to C atoms were placed in calculated positions and treated as riding on their parent atoms with C—H = 0.93–0.98 Å, Uiso(H) = 1.5Ueq(C) for methyl H atoms and 1.2Ueq(C) for the opthers. As no significant anomalous scatterings, Friedel pairs were merged, the enantiomer has been assigned by reference to an unchanging chiral centre in the synthetic procedure.

Computing details top

Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction: CrystalClear (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids.
[Figure 2] Fig. 2. A partial packing view, showing the hydrogen bonding chain structure along [010].
Triethylammonium (2R,3R)-2,3-bis(benzoyloxy)-3-carboxypropanoate top
Crystal data top
C6H16N+·C18H13O8F(000) = 976
Mr = 459.48Dx = 1.314 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 17618 reflections
a = 11.2148 (12) Åθ = 2.4–28.3°
b = 12.9835 (13) ŵ = 0.10 mm1
c = 15.9499 (17) ÅT = 293 K
V = 2322.4 (4) Å3Block, colorless
Z = 40.20 × 0.20 × 0.18 mm
Data collection top
Rigaku R-AXIS RAPID
diffractometer
2336 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.067
Graphite monochromatorθmax = 28.3°, θmin = 2.4°
ω scanh = 1414
17272 measured reflectionsk = 1717
3242 independent reflectionsl = 2118
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)] = 0.042Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.095H atoms treated by a mixture of independent and constrained refinement
S = 1.02 w = 1/[σ2(Fo2) + (0.0431P)2 + 0.0369P]
where P = (Fo2 + 2Fc2)/3
3242 reflections(Δ/σ)max < 0.001
309 parametersΔρmax = 0.20 e Å3
0 restraintsΔρmin = 0.21 e Å3
Crystal data top
C6H16N+·C18H13O8V = 2322.4 (4) Å3
Mr = 459.48Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 11.2148 (12) ŵ = 0.10 mm1
b = 12.9835 (13) ÅT = 293 K
c = 15.9499 (17) Å0.20 × 0.20 × 0.18 mm
Data collection top
Rigaku R-AXIS RAPID
diffractometer
2336 reflections with I > 2σ(I)
17272 measured reflectionsRint = 0.067
3242 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0420 restraints
wR(F2) = 0.095H atoms treated by a mixture of independent and constrained refinement
S = 1.02Δρmax = 0.20 e Å3
3242 reflectionsΔρmin = 0.21 e Å3
309 parameters
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.

Refinement. merg 4 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 > 2sigma(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
C10.8315 (2)0.31475 (18)0.91650 (17)0.0256 (6)
C20.7651 (2)0.3345 (2)0.98812 (17)0.0318 (6)
H20.77370.39711.01570.038*
C30.6859 (3)0.2615 (2)1.01896 (18)0.0355 (7)
H30.64120.27521.06680.043*
C40.6740 (2)0.1687 (2)0.97802 (19)0.0366 (7)
H40.62150.11950.99880.044*
C50.7395 (2)0.14762 (19)0.90625 (18)0.0329 (6)
H50.73060.08480.87900.039*
C60.8185 (2)0.22080 (18)0.87521 (17)0.0272 (6)
H60.86250.20710.82710.033*
C70.9139 (2)0.3955 (2)0.88549 (16)0.0267 (6)
C81.0565 (2)0.43421 (16)0.77853 (17)0.0239 (5)
H81.06920.49330.81570.029*
C91.1775 (2)0.38534 (17)0.75872 (16)0.0241 (5)
C100.9965 (2)0.47203 (17)0.69826 (16)0.0237 (5)
H101.05680.50270.66140.028*
C110.8990 (2)0.55163 (17)0.71601 (18)0.0273 (6)
C120.9025 (2)0.3985 (2)0.58089 (18)0.0283 (6)
C130.8401 (2)0.30655 (18)0.54713 (17)0.0284 (6)
C140.8626 (2)0.2078 (2)0.5773 (2)0.0362 (7)
H140.91700.19780.62050.043*
C150.8031 (3)0.1247 (2)0.5423 (2)0.0437 (8)
H150.81910.05840.56140.052*
C160.7203 (3)0.1396 (2)0.4795 (2)0.0432 (8)
H160.68060.08340.45660.052*
C170.6964 (3)0.2369 (2)0.45069 (19)0.0411 (7)
H170.63940.24670.40910.049*
C180.7572 (2)0.3209 (2)0.48357 (18)0.0363 (7)
H180.74230.38670.46300.044*
C190.5614 (2)0.4077 (2)0.7214 (2)0.0410 (7)
H19A0.63690.37140.72200.049*
H19B0.56530.46190.76310.049*
C200.5432 (3)0.4554 (3)0.6361 (2)0.0549 (9)
H20A0.46590.48710.63370.082*
H20B0.54860.40300.59380.082*
H20C0.60340.50660.62650.082*
C210.4518 (3)0.2449 (2)0.6854 (2)0.0455 (8)
H21A0.43500.27090.62960.055*
H21B0.38410.20370.70290.055*
C220.5604 (3)0.1767 (2)0.6811 (3)0.0685 (11)
H22A0.57520.14710.73530.103*
H22B0.62810.21680.66410.103*
H22C0.54700.12260.64110.103*
C230.4718 (3)0.2984 (2)0.83353 (18)0.0391 (7)
H23A0.54990.26840.84290.047*
H23B0.41290.24470.84240.047*
C240.4518 (3)0.3828 (2)0.89667 (19)0.0479 (8)
H24A0.37970.41910.88320.072*
H24B0.51790.42980.89540.072*
H24C0.44510.35340.95170.072*
N10.46413 (19)0.33463 (16)0.74420 (14)0.0308 (5)
H1010.391 (3)0.372 (2)0.7409 (18)0.045 (8)*
O10.98006 (14)0.36173 (11)0.82011 (11)0.0255 (4)
O20.92394 (19)0.48083 (14)0.91440 (14)0.0451 (6)
O31.19370 (14)0.29069 (12)0.76840 (12)0.0313 (4)
O41.25517 (14)0.44777 (12)0.73477 (13)0.0334 (4)
O50.94968 (15)0.64074 (12)0.73381 (13)0.0339 (4)
H510.891 (3)0.691 (2)0.735 (2)0.076 (11)*
O60.79444 (15)0.53471 (14)0.71332 (15)0.0447 (6)
O70.94704 (15)0.38233 (11)0.65836 (11)0.0270 (4)
O80.91205 (18)0.47972 (14)0.54453 (13)0.0425 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0253 (11)0.0246 (13)0.0270 (15)0.0042 (10)0.0020 (11)0.0015 (11)
C20.0355 (14)0.0283 (13)0.0315 (16)0.0038 (12)0.0048 (13)0.0028 (12)
C30.0363 (14)0.0421 (16)0.0283 (17)0.0065 (13)0.0100 (13)0.0046 (13)
C40.0322 (14)0.0350 (15)0.0426 (18)0.0020 (13)0.0084 (13)0.0103 (14)
C50.0306 (13)0.0243 (13)0.0437 (18)0.0006 (11)0.0014 (13)0.0002 (12)
C60.0255 (12)0.0265 (12)0.0295 (15)0.0030 (11)0.0031 (11)0.0018 (11)
C70.0268 (13)0.0246 (13)0.0285 (15)0.0013 (11)0.0008 (11)0.0025 (11)
C80.0263 (11)0.0161 (10)0.0294 (14)0.0049 (10)0.0002 (12)0.0022 (10)
C90.0246 (12)0.0202 (11)0.0274 (15)0.0021 (10)0.0035 (11)0.0014 (10)
C100.0243 (12)0.0172 (10)0.0296 (15)0.0023 (10)0.0013 (11)0.0000 (10)
C110.0249 (12)0.0187 (11)0.0383 (17)0.0009 (10)0.0017 (12)0.0025 (11)
C120.0277 (12)0.0270 (13)0.0303 (16)0.0037 (11)0.0007 (12)0.0006 (12)
C130.0257 (12)0.0303 (14)0.0294 (16)0.0040 (11)0.0025 (12)0.0026 (12)
C140.0358 (15)0.0296 (14)0.0431 (19)0.0004 (12)0.0113 (13)0.0021 (13)
C150.0478 (17)0.0294 (14)0.054 (2)0.0012 (14)0.0105 (16)0.0101 (15)
C160.0404 (16)0.0432 (17)0.046 (2)0.0043 (14)0.0063 (15)0.0155 (15)
C170.0354 (15)0.0553 (19)0.0327 (18)0.0036 (14)0.0099 (14)0.0102 (15)
C180.0354 (14)0.0421 (16)0.0314 (17)0.0063 (13)0.0029 (13)0.0019 (13)
C190.0281 (13)0.0426 (15)0.052 (2)0.0040 (12)0.0004 (15)0.0036 (15)
C200.0392 (17)0.069 (2)0.057 (2)0.0049 (17)0.0068 (16)0.0195 (18)
C210.0456 (17)0.0407 (16)0.050 (2)0.0039 (15)0.0022 (16)0.0131 (15)
C220.060 (2)0.0522 (19)0.093 (3)0.0086 (18)0.020 (2)0.022 (2)
C230.0418 (16)0.0371 (15)0.0383 (18)0.0030 (13)0.0024 (14)0.0056 (14)
C240.0506 (18)0.0524 (18)0.0405 (19)0.0004 (16)0.0060 (16)0.0023 (15)
N10.0242 (10)0.0305 (11)0.0378 (15)0.0030 (9)0.0022 (10)0.0008 (10)
O10.0282 (8)0.0192 (8)0.0291 (10)0.0022 (7)0.0072 (8)0.0021 (7)
O20.0550 (13)0.0276 (10)0.0527 (14)0.0101 (9)0.0192 (11)0.0143 (10)
O30.0269 (9)0.0192 (8)0.0477 (12)0.0003 (7)0.0017 (9)0.0023 (9)
O40.0238 (8)0.0243 (8)0.0522 (13)0.0013 (8)0.0029 (9)0.0083 (9)
O50.0264 (8)0.0164 (8)0.0590 (13)0.0011 (7)0.0004 (9)0.0024 (9)
O60.0221 (9)0.0313 (9)0.0805 (17)0.0026 (8)0.0022 (10)0.0082 (11)
O70.0337 (9)0.0179 (8)0.0292 (11)0.0028 (7)0.0062 (8)0.0009 (7)
O80.0509 (12)0.0318 (10)0.0448 (13)0.0052 (9)0.0112 (11)0.0133 (10)
Geometric parameters (Å, º) top
C1—C21.388 (4)C14—H140.9300
C1—C61.394 (3)C15—C161.380 (4)
C1—C71.482 (3)C15—H150.9300
C2—C31.389 (4)C16—C171.371 (4)
C2—H20.9300C16—H160.9300
C3—C41.377 (4)C17—C181.389 (4)
C3—H30.9300C17—H170.9300
C4—C51.387 (4)C18—H180.9300
C4—H40.9300C19—N11.491 (3)
C5—C61.390 (4)C19—C201.508 (4)
C5—H50.9300C19—H19A0.9700
C6—H60.9300C19—H19B0.9700
C7—O21.205 (3)C20—H20A0.9600
C7—O11.353 (3)C20—H20B0.9600
C8—O11.435 (3)C20—H20C0.9600
C8—C101.527 (3)C21—N11.502 (3)
C8—C91.532 (3)C21—C221.507 (4)
C8—H80.9800C21—H21A0.9700
C9—O41.249 (3)C21—H21B0.9700
C9—O31.252 (3)C22—H22A0.9600
C10—O71.439 (3)C22—H22B0.9600
C10—C111.531 (3)C22—H22C0.9600
C10—H100.9800C23—N11.503 (4)
C11—O61.194 (3)C23—C241.505 (4)
C11—O51.320 (3)C23—H23A0.9700
C12—O81.208 (3)C23—H23B0.9700
C12—O71.349 (3)C24—H24A0.9600
C12—C131.485 (3)C24—H24B0.9600
C13—C181.388 (4)C24—H24C0.9600
C13—C141.392 (4)N1—H1010.95 (3)
C14—C151.386 (4)O5—H510.93 (4)
C2—C1—C6119.6 (2)C15—C16—H16119.8
C2—C1—C7118.6 (2)C16—C17—C18120.1 (3)
C6—C1—C7121.8 (2)C16—C17—H17120.0
C1—C2—C3120.6 (3)C18—C17—H17120.0
C1—C2—H2119.7C13—C18—C17119.9 (3)
C3—C2—H2119.7C13—C18—H18120.0
C4—C3—C2119.4 (3)C17—C18—H18120.0
C4—C3—H3120.3N1—C19—C20112.5 (2)
C2—C3—H3120.3N1—C19—H19A109.1
C3—C4—C5120.9 (2)C20—C19—H19A109.1
C3—C4—H4119.6N1—C19—H19B109.1
C5—C4—H4119.6C20—C19—H19B109.1
C4—C5—C6119.8 (2)H19A—C19—H19B107.8
C4—C5—H5120.1C19—C20—H20A109.5
C6—C5—H5120.1C19—C20—H20B109.5
C5—C6—C1119.8 (2)H20A—C20—H20B109.5
C5—C6—H6120.1C19—C20—H20C109.5
C1—C6—H6120.1H20A—C20—H20C109.5
O2—C7—O1122.8 (2)H20B—C20—H20C109.5
O2—C7—C1125.5 (2)N1—C21—C22114.2 (3)
O1—C7—C1111.7 (2)N1—C21—H21A108.7
O1—C8—C10109.60 (19)C22—C21—H21A108.7
O1—C8—C9110.67 (17)N1—C21—H21B108.7
C10—C8—C9110.5 (2)C22—C21—H21B108.7
O1—C8—H8108.7H21A—C21—H21B107.6
C10—C8—H8108.7C21—C22—H22A109.5
C9—C8—H8108.7C21—C22—H22B109.5
O4—C9—O3125.0 (2)H22A—C22—H22B109.5
O4—C9—C8114.34 (19)C21—C22—H22C109.5
O3—C9—C8120.6 (2)H22A—C22—H22C109.5
O7—C10—C8106.28 (17)H22B—C22—H22C109.5
O7—C10—C11110.67 (19)N1—C23—C24113.4 (2)
C8—C10—C11112.1 (2)N1—C23—H23A108.9
O7—C10—H10109.2C24—C23—H23A108.9
C8—C10—H10109.2N1—C23—H23B108.9
C11—C10—H10109.2C24—C23—H23B108.9
O6—C11—O5126.3 (2)H23A—C23—H23B107.7
O6—C11—C10124.8 (2)C23—C24—H24A109.5
O5—C11—C10108.9 (2)C23—C24—H24B109.5
O8—C12—O7122.9 (2)H24A—C24—H24B109.5
O8—C12—C13124.7 (2)C23—C24—H24C109.5
O7—C12—C13112.4 (2)H24A—C24—H24C109.5
C18—C13—C14119.8 (2)H24B—C24—H24C109.5
C18—C13—C12118.2 (2)C19—N1—C21114.1 (2)
C14—C13—C12122.0 (2)C19—N1—C23112.9 (2)
C15—C14—C13119.4 (3)C21—N1—C23110.8 (2)
C15—C14—H14120.3C19—N1—H101107.3 (17)
C13—C14—H14120.3C21—N1—H101106.1 (17)
C16—C15—C14120.4 (3)C23—N1—H101105.0 (18)
C16—C15—H15119.8C7—O1—C8118.11 (18)
C14—C15—H15119.8C11—O5—H51108 (2)
C17—C16—C15120.3 (3)C12—O7—C10114.96 (18)
C17—C16—H16119.8
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H101···O4i0.95 (3)1.82 (3)2.770 (3)177 (3)
O5—H51···O3ii0.93 (4)1.60 (3)2.525 (2)171 (3)
Symmetry codes: (i) x1, y, z; (ii) x+2, y+1/2, z+3/2.

Experimental details

Crystal data
Chemical formulaC6H16N+·C18H13O8
Mr459.48
Crystal system, space groupOrthorhombic, P212121
Temperature (K)293
a, b, c (Å)11.2148 (12), 12.9835 (13), 15.9499 (17)
V3)2322.4 (4)
Z4
Radiation typeMo Kα
µ (mm1)0.10
Crystal size (mm)0.20 × 0.20 × 0.18
Data collection
DiffractometerRigaku R-AXIS RAPID
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
17272, 3242, 2336
Rint0.067
(sin θ/λ)max1)0.667
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.095, 1.02
No. of reflections3242
No. of parameters309
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.20, 0.21

Computer programs: RAPID-AUTO (Rigaku, 1998), CrystalClear (Rigaku/MSC, 2002), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H101···O4i0.95 (3)1.82 (3)2.770 (3)177 (3)
O5—H51···O3ii0.93 (4)1.60 (3)2.525 (2)171 (3)
Symmetry codes: (i) x1, y, z; (ii) x+2, y+1/2, z+3/2.
 

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (grant Nos. 20872030 and 20972043) and Heilongjiang University, China.

References

First citationKassai, C., Juvancz, Z., BaAlint, J., Fogassy, E. & Kozma, D. (2000). Tetrahedron, 56, 8355–8359.  Web of Science CrossRef CAS Google Scholar
First citationRigaku (1998). RAPID-AUTO. Rigaku Corporation, Tokyo, Japan.  Google Scholar
First citationRigaku/MSC (2002). CrystalClear. Rigaku/MSC Inc., The Woodlands, Texas, USA.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationTan, B., Luo, G.-S., Qi, X. & Wang, J.-D. (2006). Sep. Purif. Technol. A, 49, 186–191.  Web of Science CrossRef CAS Google Scholar

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