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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

4,4′-[p-Phenyl­enebis(­­oxy)]di­butanoic acid

aDepartment of Chemistry, School of Science, Beijing Jiaotong University, No. 3 Shang Yuan Cun Road, HaiDian District 100044, People's Republic of China
*Correspondence e-mail: zhili@bjtu.edu.cn

(Received 5 September 2011; accepted 10 September 2011; online 17 September 2011)

The complete mol­ecule of the title compound, C14H18O6, has a center of inversion at the centroid of the benzene ring and the asymmetric unit contains one half-mol­ecule. The conformation of the side chain is anti [C—C—C—C = −171.40 (17)°]. In the crystal, pairs of head-to-head carb­oxy­lic acid O—H⋯O hydrogen bonds link the mol­ecules into infinite zigzag chains propagating along [130]. Weak C—H⋯π inter­actions between adjacent chains expand the structure into a layered network in the ac plane.

Related literature

For general background to phen­oxy­acetic acid derivatives, see: Yada (1959[Yada, N. (1959). Makromol. Chem. 32, 1-12.]); Zheng et al. (2007[Zheng, Z.-B., Wu, R.-T., Ji, N.-N. & Sun, Y.-F. (2007). Acta Cryst. E63, o3936.]); Deng et al. (2010[Deng, R. H., Chen, D. H., Lai, B. W. & Wen, H. L. (2010). Z. Kristallogr. New Cryst. Struct. 225, 719-720.]); Xiong et al. (2010[Xiong, Z. Q., Liu, C. B. & Gong, Y. N. (2010). Z. Kristallogr. New Cryst. Struct. 225, 763-764.]); Fu et al. (2011[Fu, C.-Y., Liu, Y.-H., Zhou, Z.-L. & Tang, H. (2011). Acta Cryst. E67, o1048.]). For related structures of multidentate O-donor ligands such as benzene-1,4-di­oxy­diacetic acid and benzene-1,4-di­oxy­dibutanoic acid, see: Dai et al. (2009[Dai, Y. M., Tang, E., Huang, J. F., Yao, Y. G. & Huang, X. D. (2009). J. Mol. Struct. 918, 183-187.]); Zhu et al. (2008[Zhu, L., Zhu, H. & Sun, F. (2008). Acta Cryst. E64, m57.]); Li et al. (2010[Li, X. Y., Liu, C. B., Che, G. B., Wang, X. C., Li, C. X., Yan, Y. S. & Guan, Q. F. (2010). Inorg. Chim. Acta, 363, 1359-1366.]); Yang et al. (2010[Yang, Y., Tan, M. X., Li, X., Chen, X. M., Chen, G. Q., Qin, R. H. & Duan, W. G. (2010). J. Mol. Struct. 975, 372-375.]); Zhao (2011[Zhao, Y.-Y. (2011). Acta Cryst. E67, m138.]). For the synthesis of the title compound, see: Zhang et al. (2009[Zhang, T., Fan, H. L., Zhou, J. G. & Jin, Q. H. (2009). J. Polym. Sci. Part A Polym. Chem. 47, 3056-3065.]). For standard bond lengths, see: Allen et al. (1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. J. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1-19.]).

[Scheme 1]

Experimental

Crystal data
  • C14H18O6

  • Mr = 282.28

  • Triclinic, [P \overline 1]

  • a = 4.8389 (11) Å

  • b = 6.6300 (15) Å

  • c = 11.406 (3) Å

  • α = 83.067 (5)°

  • β = 81.249 (5)°

  • γ = 71.095 (4)°

  • V = 341.16 (13) Å3

  • Z = 1

  • Mo Kα radiation

  • μ = 0.11 mm−1

  • T = 296 K

  • 0.21 × 0.19 × 0.18 mm

Data collection
  • Bruker SMART CCD diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.978, Tmax = 0.981

  • 1861 measured reflections

  • 1170 independent reflections

  • 1025 reflections with I > 2σ(I)

  • Rint = 0.023

Refinement
  • R[F2 > 2σ(F2)] = 0.050

  • wR(F2) = 0.162

  • S = 1.02

  • 1170 reflections

  • 92 parameters

  • H-atom parameters constrained

  • Δρmax = 0.30 e Å−3

  • Δρmin = −0.20 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

Cg1 is the centroid of the C5–C7/C5′–C7′ ring.

D—H⋯A D—H H⋯A DA D—H⋯A
O2—H2⋯O1i 0.82 1.85 2.668 (3) 174
C4—H4BCg1ii 0.97 2.89 3.703 (3) 142
Symmetry codes: (i) -x+2, -y-1, -z+1; (ii) x+1, y, z.

Data collection: SMART (Bruker, 2007[Bruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2007[Bruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; 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: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

Compounds of the phenoxyacetic acid and their derivatives have good herbicidal activity and become excellent plant growth regulators (Yada, 1959; Zheng et al., 2007; Deng et al., 2010; Xiong et al., 2010; Fu et al., 2011). Also, the two phenoxyacetate moieties have versatile flexiable bonding fashions to metal ions and easily forms coordination polymers (Dai et al., 2009; Zhu et al., 2008; Li et al., 2010; Yang et al., 2010; Zhao et al., 2011). Benzene-1,4-dioxydibutanoic acid is an interesting dicarboxylate ligand and its cobalt polymer has been reported by Zhao et al. 2011. To further investigate this family of ligands, the title compound, (I), was synthesized and its structure was confirmed by X-ray diffraction. X-ray diffraction analysis reveals that the asymmetric unit of the title compound contains one half-molecule and has a crystallographic inversion center at the centroid of the benzene ring (Fig. 1). The benzene-connected portions of the alkoxy substituents lie almost coplanar with the C3–C4–O3–C5 torsion angle of 176.81 (16)°. In the molecule of (I) (Fig. 1) the bond lengths are within normal ranges (Allen et al., 1987). The C1—O2, C4—O3 and C5—O3 bond length of 1.287 (3), 1.428 (2) and 1.375 (2) Å, respectively, indicate the presence of typical single bonds. Whereas the C1–O1 [1.221 (3) Å] bond lengths correspond to a typical CO bond.

In the crystal structure, it is noteworthy that pairs of intermolecular O—H···O hydrogen bonds link head-to-tail the molecules into infinite 1 d chains along the [1 3 0] direction (Fig. 2). Neighboring 1 d chains are in turn interacting with each other through C—H···π stacking interactions with the H···π distances of 2.89 (3) Å to form infinite stacks along b axis, thus leading to an interwoven two dimensional network held together by O—H···O interactions and C—H···π stacking (Fig. 3).

Related literature top

For general background to phenoxyacetic acid derivatives, see: Yada (1959); Zheng et al. (2007); Deng et al. (2010); Xiong et al. (2010); Fu et al. (2011). For related structures of multidentate O-donor ligands such as benzene-1,4-dioxydiacetic acid and benzene-1,4-dioxydibutanoic acid, see: Dai et al. (2009); Zhu et al. (2008); Li et al. (2010); Yang et al. (2010); Zhao et al. (2011). For the synthesis of the title compound, see: Zhang et al. (2009). For standard bond lengths, see: Allen et al. (1987).

Experimental top

Reagents and solvents were of commercially available quality. The title compound was synthesized according to the method of Zhang et al. 2009. To a solution of p-dihydroxybenzene (0.01 mol) in acetonitrile (50 ml), anhydrous potassium carbonate (0.02 mol) and ethyl 4-bromobutanoate (0.01 mol) were mixed. The mixture solution was refluxed for 6 h and filtered. The filtrate was evaporated under reduced pressure and the solid product was dissolved in water/ethanol (1:2 v/v), then sodium hydroxide (0.02 mol) was added. The solution was refluxed for another 24 h, then acidified with dilute HCl. The crude product was separated by filtration and crystals of the title compound were prepared by recrystallization from a mixture of water and ethanol (1:1 v/v).

Refinement top

All H atoms were placed in idealized positions (C—H = 0.93–0.97 Å, O—H = 0.82 Å and refined as riding atoms with Uiso(H) = 1.2Ueq(C) and with Uiso(H) = 1.5Ueq(O).

Structure description top

Compounds of the phenoxyacetic acid and their derivatives have good herbicidal activity and become excellent plant growth regulators (Yada, 1959; Zheng et al., 2007; Deng et al., 2010; Xiong et al., 2010; Fu et al., 2011). Also, the two phenoxyacetate moieties have versatile flexiable bonding fashions to metal ions and easily forms coordination polymers (Dai et al., 2009; Zhu et al., 2008; Li et al., 2010; Yang et al., 2010; Zhao et al., 2011). Benzene-1,4-dioxydibutanoic acid is an interesting dicarboxylate ligand and its cobalt polymer has been reported by Zhao et al. 2011. To further investigate this family of ligands, the title compound, (I), was synthesized and its structure was confirmed by X-ray diffraction. X-ray diffraction analysis reveals that the asymmetric unit of the title compound contains one half-molecule and has a crystallographic inversion center at the centroid of the benzene ring (Fig. 1). The benzene-connected portions of the alkoxy substituents lie almost coplanar with the C3–C4–O3–C5 torsion angle of 176.81 (16)°. In the molecule of (I) (Fig. 1) the bond lengths are within normal ranges (Allen et al., 1987). The C1—O2, C4—O3 and C5—O3 bond length of 1.287 (3), 1.428 (2) and 1.375 (2) Å, respectively, indicate the presence of typical single bonds. Whereas the C1–O1 [1.221 (3) Å] bond lengths correspond to a typical CO bond.

In the crystal structure, it is noteworthy that pairs of intermolecular O—H···O hydrogen bonds link head-to-tail the molecules into infinite 1 d chains along the [1 3 0] direction (Fig. 2). Neighboring 1 d chains are in turn interacting with each other through C—H···π stacking interactions with the H···π distances of 2.89 (3) Å to form infinite stacks along b axis, thus leading to an interwoven two dimensional network held together by O—H···O interactions and C—H···π stacking (Fig. 3).

For general background to phenoxyacetic acid derivatives, see: Yada (1959); Zheng et al. (2007); Deng et al. (2010); Xiong et al. (2010); Fu et al. (2011). For related structures of multidentate O-donor ligands such as benzene-1,4-dioxydiacetic acid and benzene-1,4-dioxydibutanoic acid, see: Dai et al. (2009); Zhu et al. (2008); Li et al. (2010); Yang et al. (2010); Zhao et al. (2011). For the synthesis of the title compound, see: Zhang et al. (2009). For standard bond lengths, see: Allen et al. (1987).

Computing details top

Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (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, with displacement ellipsoids at the 30% probability level. Symmetry code: (i) -x, 1 - y, -z.
[Figure 2] Fig. 2. Part of the zigzag infinite chain structure of the title compound, linked via hydrogen bonds (dashed lines) lying in the [1 3 0] direction. H atoms have been omitted for clarity, except for those involved in hydrogen-bonded interactions.
[Figure 3] Fig. 3. Part of 2 d the crystal structure showing hydrogen bonds and C—H···π contants as dashed lines. H atoms, except for those involved in hydrogen bonds, are not included.
4,4'-[p-Phenylenebis(oxy)]dibutanoic acid top
Crystal data top
C14H18O6Z = 1
Mr = 282.28F(000) = 150
Triclinic, P1Dx = 1.374 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 4.8389 (11) ÅCell parameters from 1172 reflections
b = 6.6300 (15) Åθ = 3.3–29.3°
c = 11.406 (3) ŵ = 0.11 mm1
α = 83.067 (5)°T = 296 K
β = 81.249 (5)°Block, colorless
γ = 71.095 (4)°0.21 × 0.19 × 0.18 mm
V = 341.16 (13) Å3
Data collection top
Bruker SMART CCD
diffractometer
1170 independent reflections
Radiation source: fine-focus sealed tube1025 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.023
φ and ω scansθmax = 25.0°, θmin = 1.8°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 55
Tmin = 0.978, Tmax = 0.981k = 67
1861 measured reflectionsl = 1311
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)] = 0.050Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.162H-atom parameters constrained
S = 1.02 w = 1/[σ2(Fo2) + (0.0972P)2 + 0.1511P]
where P = (Fo2 + 2Fc2)/3
1170 reflections(Δ/σ)max < 0.001
92 parametersΔρmax = 0.30 e Å3
0 restraintsΔρmin = 0.20 e Å3
Crystal data top
C14H18O6γ = 71.095 (4)°
Mr = 282.28V = 341.16 (13) Å3
Triclinic, P1Z = 1
a = 4.8389 (11) ÅMo Kα radiation
b = 6.6300 (15) ŵ = 0.11 mm1
c = 11.406 (3) ÅT = 296 K
α = 83.067 (5)°0.21 × 0.19 × 0.18 mm
β = 81.249 (5)°
Data collection top
Bruker SMART CCD
diffractometer
1170 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1025 reflections with I > 2σ(I)
Tmin = 0.978, Tmax = 0.981Rint = 0.023
1861 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0500 restraints
wR(F2) = 0.162H-atom parameters constrained
S = 1.02Δρmax = 0.30 e Å3
1170 reflectionsΔρmin = 0.20 e Å3
92 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 > 2σ(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
O10.9691 (4)0.2476 (3)0.45159 (18)0.0672 (6)
O20.7156 (4)0.4427 (3)0.40552 (18)0.0663 (6)
H20.81710.53170.45090.099*
O30.4183 (3)0.2151 (2)0.13043 (12)0.0412 (5)
C10.7769 (4)0.2666 (3)0.39978 (17)0.0364 (5)
C20.5900 (4)0.0856 (3)0.32641 (18)0.0410 (6)
H2A0.40160.02550.37300.049*
H2B0.55360.14150.25750.049*
C30.7239 (5)0.0911 (3)0.28431 (19)0.0415 (6)
H3A0.78740.13330.35160.050*
H3B0.89650.03710.22760.050*
C40.5123 (5)0.2853 (3)0.22662 (18)0.0409 (5)
H4A0.34480.34800.28370.049*
H4B0.60900.39200.19730.049*
C50.2114 (4)0.3636 (3)0.06782 (16)0.0328 (5)
C60.1047 (4)0.5809 (3)0.08497 (18)0.0375 (5)
H60.17440.63550.14170.045*
C70.1059 (4)0.2846 (3)0.01715 (17)0.0373 (5)
H70.17750.13940.02880.045*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0781 (12)0.0427 (10)0.0919 (14)0.0226 (9)0.0584 (11)0.0239 (9)
O20.0855 (14)0.0421 (10)0.0817 (13)0.0260 (9)0.0510 (11)0.0240 (8)
O30.0462 (9)0.0296 (8)0.0429 (8)0.0002 (6)0.0218 (6)0.0041 (6)
C10.0388 (10)0.0319 (11)0.0358 (10)0.0068 (8)0.0098 (8)0.0033 (8)
C20.0387 (11)0.0388 (12)0.0417 (11)0.0058 (9)0.0149 (9)0.0063 (9)
C30.0424 (11)0.0360 (11)0.0446 (12)0.0072 (9)0.0207 (9)0.0086 (9)
C40.0460 (11)0.0323 (11)0.0431 (11)0.0073 (9)0.0192 (9)0.0056 (8)
C50.0313 (9)0.0295 (10)0.0334 (10)0.0044 (8)0.0095 (7)0.0065 (7)
C60.0420 (11)0.0323 (11)0.0377 (10)0.0075 (8)0.0140 (8)0.0002 (8)
C70.0428 (11)0.0252 (9)0.0394 (11)0.0032 (8)0.0109 (8)0.0016 (7)
Geometric parameters (Å, º) top
O1—C11.221 (3)C3—H3A0.9700
O2—C11.287 (3)C3—H3B0.9700
O2—H20.8200C4—H4A0.9700
O3—C51.375 (2)C4—H4B0.9700
O3—C41.428 (2)C5—C71.386 (3)
C1—C21.498 (3)C5—C61.391 (3)
C2—C31.512 (3)C6—C7i1.385 (3)
C2—H2A0.9700C6—H60.9300
C2—H2B0.9700C7—C6i1.385 (3)
C3—C41.512 (3)C7—H70.9300
C1—O2—H2109.5H3A—C3—H3B107.8
C5—O3—C4117.68 (15)O3—C4—C3107.15 (16)
O1—C1—O2122.66 (18)O3—C4—H4A110.3
O1—C1—C2122.65 (18)C3—C4—H4A110.3
O2—C1—C2114.68 (18)O3—C4—H4B110.3
C1—C2—C3114.15 (16)C3—C4—H4B110.3
C1—C2—H2A108.7H4A—C4—H4B108.5
C3—C2—H2A108.7O3—C5—C7115.72 (16)
C1—C2—H2B108.7O3—C5—C6124.72 (18)
C3—C2—H2B108.7C7—C5—C6119.56 (18)
H2A—C2—H2B107.6C7i—C6—C5119.61 (19)
C4—C3—C2112.76 (16)C7i—C6—H6120.2
C4—C3—H3A109.0C5—C6—H6120.2
C2—C3—H3A109.0C6i—C7—C5120.83 (18)
C4—C3—H3B109.0C6i—C7—H7119.6
C2—C3—H3B109.0C5—C7—H7119.6
O1—C1—C2—C321.4 (3)C4—O3—C5—C65.5 (3)
O2—C1—C2—C3159.7 (2)O3—C5—C6—C7i179.46 (17)
C1—C2—C3—C4171.40 (17)C7—C5—C6—C7i0.1 (3)
C5—O3—C4—C3176.81 (16)O3—C5—C7—C6i179.49 (16)
C2—C3—C4—O357.1 (2)C6—C5—C7—C6i0.1 (3)
C4—O3—C5—C7174.06 (17)
Symmetry code: (i) x, y+1, z.
Hydrogen-bond geometry (Å, º) top
Cg1 is the centroid of the C5–C7/C5'–C7' ring.
D—H···AD—HH···AD···AD—H···A
O2—H2···O1ii0.821.852.668 (3)174
C4—H4B···Cg1iii0.972.893.703 (3)142
Symmetry codes: (ii) x+2, y1, z+1; (iii) x+1, y, z.

Experimental details

Crystal data
Chemical formulaC14H18O6
Mr282.28
Crystal system, space groupTriclinic, P1
Temperature (K)296
a, b, c (Å)4.8389 (11), 6.6300 (15), 11.406 (3)
α, β, γ (°)83.067 (5), 81.249 (5), 71.095 (4)
V3)341.16 (13)
Z1
Radiation typeMo Kα
µ (mm1)0.11
Crystal size (mm)0.21 × 0.19 × 0.18
Data collection
DiffractometerBruker SMART CCD
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.978, 0.981
No. of measured, independent and
observed [I > 2σ(I)] reflections
1861, 1170, 1025
Rint0.023
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.050, 0.162, 1.02
No. of reflections1170
No. of parameters92
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.30, 0.20

Computer programs: SMART (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
Cg1 is the centroid of the C5–C7/C5'–C7' ring.
D—H···AD—HH···AD···AD—H···A
O2—H2···O1i0.821.852.668 (3)174
C4—H4B···Cg1ii0.972.893.703 (3)142
Symmetry codes: (i) x+2, y1, z+1; (ii) x+1, y, z.
 

Acknowledgements

The author thanks Beijing Jiaotong University for financial support.

References

First citationAllen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. J. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.  CrossRef Google Scholar
First citationBruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationDai, Y. M., Tang, E., Huang, J. F., Yao, Y. G. & Huang, X. D. (2009). J. Mol. Struct. 918, 183–187.  CSD CrossRef CAS Google Scholar
First citationDeng, R. H., Chen, D. H., Lai, B. W. & Wen, H. L. (2010). Z. Kristallogr. New Cryst. Struct. 225, 719–720.  CAS Google Scholar
First citationFu, C.-Y., Liu, Y.-H., Zhou, Z.-L. & Tang, H. (2011). Acta Cryst. E67, o1048.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationLi, X. Y., Liu, C. B., Che, G. B., Wang, X. C., Li, C. X., Yan, Y. S. & Guan, Q. F. (2010). Inorg. Chim. Acta, 363, 1359–1366.  Web of Science CSD CrossRef CAS Google Scholar
First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationXiong, Z. Q., Liu, C. B. & Gong, Y. N. (2010). Z. Kristallogr. New Cryst. Struct. 225, 763–764.  CAS Google Scholar
First citationYada, N. (1959). Makromol. Chem. 32, 1–12.  Google Scholar
First citationYang, Y., Tan, M. X., Li, X., Chen, X. M., Chen, G. Q., Qin, R. H. & Duan, W. G. (2010). J. Mol. Struct. 975, 372–375.  Web of Science CSD CrossRef CAS Google Scholar
First citationZhang, T., Fan, H. L., Zhou, J. G. & Jin, Q. H. (2009). J. Polym. Sci. Part A Polym. Chem. 47, 3056–3065.  Web of Science CrossRef CAS Google Scholar
First citationZhao, Y.-Y. (2011). Acta Cryst. E67, m138.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationZheng, Z.-B., Wu, R.-T., Ji, N.-N. & Sun, Y.-F. (2007). Acta Cryst. E63, o3936.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationZhu, L., Zhu, H. & Sun, F. (2008). Acta Cryst. E64, m57.  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