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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

4-(4-Iodo­anilino)-2-methyl­ene-4-oxo­butanoic acid

aMangalore University, Department of Studies in Chemistry, Mangalagangotri 574 199, India, bUniversity of Mysore, Department of Studies in Chemistry, Manasagangotri, Mysore 570 006, India, and cNelson Mandela Metropolitan University, Summerstrand Campus, Department of Chemistry, University Way, Summerstrand, PO Box 77000, Port Elizabeth, 6031, South Africa
*Correspondence e-mail: richard.betz@webmail.co.za

(Received 9 November 2012; accepted 7 December 2012; online 15 December 2012)

In the title compound, C11H10INO3, an addition product of itaconic acid anhydride and 4-iodo­aniline, the least-squares planes defined by the atoms of the aromatic moiety and the non-H atoms of the carb­oxy­lic acid group enclose an angle of 74.82 (11)°. In the crystal, classical O—H⋯O hydrogen bonds formed by carb­oxy­lic groups, as well as N—H⋯O hydrogen bonds formed by amide groups, are present along with C—H⋯O contacts. Together, these connect the mol­ecules into dimeric chains along the b-axis direction.

Related literature

For applications of itaconic acid anhydride, see: Oishi (1980[Oishi, T. (1980). Polym. J. 12, 719-727.]); Urzua et al. (1998[Urzua, M., Opazo, A., Gargallo, L. & Radic, D. (1998). Polym. Bull. 40, 63-67.]); Shetgiri & Nayak (2005[Shetgiri, N. P. & Nayak, B. K. (2005). Indian J. Chem. Sect. B, 44, 1933-1936.]); Katla et al. (2011[Katla, S., Pothana, P., Gubba, B. & Manda, S. (2011). Der Chem. Sin. 2, 47-53.]); Hanoon (2011[Hanoon, H. D. (2011). Nat. J. Chem. 41, 77-89.]). For graph-set analysis of hydrogen bonds, see: Etter et al. (1990[Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256-262.]); Bernstein et al. (1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]).

[Scheme 1]

Experimental

Crystal data
  • C11H10INO3

  • Mr = 331.10

  • Monoclinic, P 21 /c

  • a = 23.1111 (6) Å

  • b = 4.7863 (1) Å

  • c = 10.4262 (2) Å

  • β = 97.071 (1)°

  • V = 1144.54 (4) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 2.79 mm−1

  • T = 200 K

  • 0.29 × 0.16 × 0.10 mm

Data collection
  • Bruker APEXII CCD diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2008[Bruker (2008). SADABS. Bruker Inc., Madison, Wisconsin, USA.]) Tmin = 0.503, Tmax = 0.776

  • 12435 measured reflections

  • 2839 independent reflections

  • 2612 reflections with I > 2σ(I)

  • Rint = 0.015

Refinement
  • R[F2 > 2σ(F2)] = 0.018

  • wR(F2) = 0.047

  • S = 1.06

  • 2839 reflections

  • 150 parameters

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

  • Δρmax = 0.73 e Å−3

  • Δρmin = −0.61 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O1—H1⋯O2i 0.84 1.83 2.6597 (19) 170
N1—H71⋯O3ii 0.83 (2) 2.10 (2) 2.8963 (18) 161 (2)
C3—H3B⋯O3ii 0.99 2.51 3.266 (2) 134
Symmetry codes: (i) -x+1, -y, -z+1; (ii) x, y+1, z.

Data collection: APEX2 (Bruker, 2010[Bruker (2010). APEX2 and SAINT. Bruker AXS Inc., Madison, USA.]); cell refinement: SAINT (Bruker, 2010[Bruker (2010). APEX2 and SAINT. Bruker AXS Inc., Madison, 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: ORTEP-3 (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]) and Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]) and PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]).

Supporting information


Comment top

Itaconic acid anhydride is a monomeric building block obtained from renewable sources. Copolymers containing both hydrophilic and hydrophobic segments are drawing considerable attention because of their possible use in biological systems. In this aspect, N-substituted itaconamic acid derivatives have attracted attention due to their amphiphilic properties. Being more reactive than maleic anhydride, itaconic anhydride has already been applied for introducing polar functional groups into polymers (Oishi, 1980; Urzua et al.,1998). In addition, the basic skeleton of itaconic anhydride is useful for the synthesis of cyclic derivatives of imides (Shetgiri & Nayak, 2005), pyridazines (Katla et al., 2011), oxazepines and diazepines (Hanoon, 2011) which show pharmacological activity. In continuation of our studies of pharmacologically active compounds, the crystal structure of the title compound was determined.

The C=C bond is present as its anti-Saytzeff tautomer. The N–C(=O) bond length of 1.351 (2) Å is indicative of amide-type resonance. The least-squares plane defined by the atoms of the aromatic moiety on the one hand and the non-hydrogen atoms of the carboxylic acid group on the other hand enclose an angle of 74.82 (11) ° (Fig. 1).

In the crystal, C–H···O contatcs whose range falls by more than 0.1 Å below the sum of van-der-Waals radii are observed next to classical hydrogen bonds of the N–H···O and C–H···O type. The N–H···O hydrogen bonds are supported by the carbonyl oxygen atom of the amide functionality as acceptor. Simultaneously, one of the hydrogen atoms of the methylene group forms a C–H···O contact to the same oxygen atom which, therefore, acts as twofold acceptor. The carboxylic acid groups engage in the common dimeric hydrogen bonding pattern frequently encountered for many carboxylic acids. In total, the molecules are connected to dimeric chains along the crystallographic b axis. Metrical parameters as well as information about the symmetry of these contacts are summarized in Table 1. In terms of graph-set analysis (Etter et al., 1990; Bernstein et al., 1995), the descriptor for these contacts is C11(4)C11(4)R22(8) on the unary level. The shortest intercentroid distance between two aromatic systems was found at 4.7863 (11) Å which is about the length of axis b (Fig. 2).

The packing of the title compound in the crystal structure is shown in Figure 3.

Related literature top

For applications of itaconic acid anhydride, see: Oishi (1980); Urzua et al. (1998); Shetgiri & Nayak (2005); Katla et al. (2011); Hanoon (2011). For graph-set analysis of hydrogen bonds, see: Etter et al. (1990); Bernstein et al. (1995).

Experimental top

Itaconic anhydride (0.112 g, 1 mmol) was dissolved in acetone (30 ml) and 4-iodoaniline (0.219 g, 1 mmol) was added in small portions under stirring at room temperature over a timespan of 30 minutes. The mixture turned into a yellow slurry. Stirring was continued for 1.5 h after which the slurry was filtered and the solid obtained was washed with acetone and dried to yield the title compound. Single crystals suitable for the X-ray diffraction study were grown from methanol by slow evaporation at room temperature.

Refinement top

Carbon-bound H atoms were placed in calculated positions (C–H 0.95 Å for aromatic and vinylic carbon atoms, C–H 0.99 Å for methylene groups) and were included in the refinement in the riding model approximation, with U(H) set to 1.2Ueq(C). The H atom of the hydroxyl group was allowed to rotate with a fixed angle around the C–O bond to best fit the experimental electron density (HFIX 147 in the SHELX program suite (Sheldrick, 2008)), with U(H) set to 1.5Ueq(O). The nitrogen-bound H atom was located on a difference Fourier map and refined freely.

Structure description top

Itaconic acid anhydride is a monomeric building block obtained from renewable sources. Copolymers containing both hydrophilic and hydrophobic segments are drawing considerable attention because of their possible use in biological systems. In this aspect, N-substituted itaconamic acid derivatives have attracted attention due to their amphiphilic properties. Being more reactive than maleic anhydride, itaconic anhydride has already been applied for introducing polar functional groups into polymers (Oishi, 1980; Urzua et al.,1998). In addition, the basic skeleton of itaconic anhydride is useful for the synthesis of cyclic derivatives of imides (Shetgiri & Nayak, 2005), pyridazines (Katla et al., 2011), oxazepines and diazepines (Hanoon, 2011) which show pharmacological activity. In continuation of our studies of pharmacologically active compounds, the crystal structure of the title compound was determined.

The C=C bond is present as its anti-Saytzeff tautomer. The N–C(=O) bond length of 1.351 (2) Å is indicative of amide-type resonance. The least-squares plane defined by the atoms of the aromatic moiety on the one hand and the non-hydrogen atoms of the carboxylic acid group on the other hand enclose an angle of 74.82 (11) ° (Fig. 1).

In the crystal, C–H···O contatcs whose range falls by more than 0.1 Å below the sum of van-der-Waals radii are observed next to classical hydrogen bonds of the N–H···O and C–H···O type. The N–H···O hydrogen bonds are supported by the carbonyl oxygen atom of the amide functionality as acceptor. Simultaneously, one of the hydrogen atoms of the methylene group forms a C–H···O contact to the same oxygen atom which, therefore, acts as twofold acceptor. The carboxylic acid groups engage in the common dimeric hydrogen bonding pattern frequently encountered for many carboxylic acids. In total, the molecules are connected to dimeric chains along the crystallographic b axis. Metrical parameters as well as information about the symmetry of these contacts are summarized in Table 1. In terms of graph-set analysis (Etter et al., 1990; Bernstein et al., 1995), the descriptor for these contacts is C11(4)C11(4)R22(8) on the unary level. The shortest intercentroid distance between two aromatic systems was found at 4.7863 (11) Å which is about the length of axis b (Fig. 2).

The packing of the title compound in the crystal structure is shown in Figure 3.

For applications of itaconic acid anhydride, see: Oishi (1980); Urzua et al. (1998); Shetgiri & Nayak (2005); Katla et al. (2011); Hanoon (2011). For graph-set analysis of hydrogen bonds, see: Etter et al. (1990); Bernstein et al. (1995).

Computing details top

Data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2010); data reduction: SAINT (Bruker, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids drawn at 50% probability level.
[Figure 2] Fig. 2. Intermolecular contacts, viewed along [0 0 - 1]. Symmetry operators: i x, y - 1, z; ii x, y + 1, z; iii -x + 1, -y, -z + 1.
[Figure 3] Fig. 3. Molecular packing of the title compound, viewed along [0 1 0] (anisotropic displacement ellipsoids drawn at 50% probability level). Blue dashed lines indicate hydrogen bonds between the carboxylic acid groups.
4-(4-Iodoanilino)-2-methylene-4-oxobutanoic acid top
Crystal data top
C11H10INO3F(000) = 640
Mr = 331.10Dx = 1.921 Mg m3
Monoclinic, P21/cMelting point = 447–445 K
Hall symbol: -P 2ybcMo Kα radiation, λ = 0.71073 Å
a = 23.1111 (6) ÅCell parameters from 9343 reflections
b = 4.7863 (1) Åθ = 2.7–28.3°
c = 10.4262 (2) ŵ = 2.79 mm1
β = 97.071 (1)°T = 200 K
V = 1144.54 (4) Å3Rectangular, colourless
Z = 40.29 × 0.16 × 0.10 mm
Data collection top
Bruker APEXII CCD
diffractometer
2839 independent reflections
Radiation source: fine-focus sealed tube2612 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.015
φ and ω scansθmax = 28.3°, θmin = 2.7°
Absorption correction: multi-scan
(SADABS; Bruker, 2008)
h = 3030
Tmin = 0.503, Tmax = 0.776k = 66
12435 measured reflectionsl = 813
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)] = 0.018Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.047H atoms treated by a mixture of independent and constrained refinement
S = 1.06 w = 1/[σ2(Fo2) + (0.0202P)2 + 0.979P]
where P = (Fo2 + 2Fc2)/3
2839 reflections(Δ/σ)max = 0.002
150 parametersΔρmax = 0.73 e Å3
0 restraintsΔρmin = 0.61 e Å3
Crystal data top
C11H10INO3V = 1144.54 (4) Å3
Mr = 331.10Z = 4
Monoclinic, P21/cMo Kα radiation
a = 23.1111 (6) ŵ = 2.79 mm1
b = 4.7863 (1) ÅT = 200 K
c = 10.4262 (2) Å0.29 × 0.16 × 0.10 mm
β = 97.071 (1)°
Data collection top
Bruker APEXII CCD
diffractometer
2839 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2008)
2612 reflections with I > 2σ(I)
Tmin = 0.503, Tmax = 0.776Rint = 0.015
12435 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0180 restraints
wR(F2) = 0.047H atoms treated by a mixture of independent and constrained refinement
S = 1.06Δρmax = 0.73 e Å3
2839 reflectionsΔρmin = 0.61 e Å3
150 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
I10.056006 (5)0.19408 (3)0.680940 (13)0.03784 (5)
O10.48205 (6)0.1867 (3)0.34828 (13)0.0334 (3)
H10.50450.18520.41800.050*
O20.43726 (6)0.1500 (3)0.44728 (13)0.0335 (3)
O30.30129 (6)0.2166 (2)0.35760 (14)0.0301 (3)
N10.26626 (6)0.2123 (3)0.39810 (15)0.0238 (3)
H710.2679 (10)0.382 (5)0.380 (2)0.031 (6)*
C10.43994 (7)0.0058 (4)0.35485 (16)0.0232 (3)
C20.39444 (7)0.0026 (3)0.24115 (16)0.0225 (3)
C30.34191 (7)0.1767 (3)0.25648 (16)0.0232 (3)
H3A0.31980.21040.17030.028*
H3B0.35470.36010.29370.028*
C40.30202 (7)0.0375 (3)0.34331 (15)0.0202 (3)
C50.40223 (8)0.1299 (4)0.13366 (18)0.0330 (4)
H5A0.43710.23180.12860.040*
H5B0.37290.12350.06140.040*
C110.21964 (7)0.1204 (3)0.46527 (16)0.0218 (3)
C120.22773 (7)0.0842 (4)0.55994 (17)0.0263 (3)
H120.26520.16440.58230.032*
C130.18104 (8)0.1721 (4)0.62227 (18)0.0284 (4)
H130.18640.31370.68650.034*
C140.12659 (7)0.0515 (4)0.58994 (16)0.0265 (3)
C150.11850 (8)0.1576 (4)0.49805 (19)0.0308 (4)
H150.08130.24210.47770.037*
C160.16521 (8)0.2432 (4)0.43571 (18)0.0290 (4)
H160.15990.38670.37240.035*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.02465 (7)0.04793 (9)0.04370 (9)0.00628 (5)0.01530 (5)0.00051 (6)
O10.0276 (6)0.0373 (7)0.0342 (7)0.0105 (5)0.0003 (5)0.0044 (6)
O20.0336 (7)0.0386 (8)0.0276 (6)0.0087 (6)0.0003 (5)0.0064 (5)
O30.0333 (7)0.0172 (5)0.0428 (7)0.0000 (5)0.0167 (6)0.0006 (5)
N10.0239 (7)0.0160 (6)0.0331 (7)0.0002 (5)0.0096 (6)0.0033 (6)
C10.0217 (7)0.0230 (7)0.0258 (7)0.0002 (6)0.0066 (6)0.0026 (6)
C20.0204 (7)0.0216 (7)0.0262 (7)0.0017 (6)0.0060 (6)0.0036 (6)
C30.0205 (7)0.0223 (8)0.0274 (8)0.0007 (6)0.0050 (6)0.0052 (6)
C40.0179 (7)0.0194 (7)0.0230 (7)0.0010 (5)0.0011 (5)0.0009 (6)
C50.0271 (9)0.0400 (10)0.0320 (9)0.0016 (7)0.0040 (7)0.0066 (8)
C110.0201 (7)0.0201 (7)0.0261 (7)0.0020 (6)0.0064 (6)0.0024 (6)
C120.0194 (7)0.0279 (8)0.0318 (8)0.0017 (6)0.0046 (6)0.0035 (7)
C130.0251 (8)0.0316 (9)0.0294 (8)0.0007 (7)0.0072 (7)0.0045 (7)
C140.0194 (7)0.0323 (9)0.0291 (8)0.0046 (6)0.0083 (6)0.0042 (7)
C150.0182 (7)0.0390 (10)0.0356 (9)0.0038 (7)0.0055 (7)0.0012 (8)
C160.0246 (8)0.0306 (9)0.0324 (9)0.0044 (7)0.0060 (7)0.0070 (7)
Geometric parameters (Å, º) top
I1—C142.0994 (16)C3—H3B0.9900
O1—C11.311 (2)C5—H5A0.9500
O1—H10.8400C5—H5B0.9500
O2—C11.226 (2)C11—C121.387 (2)
O3—C41.2258 (19)C11—C161.388 (2)
N1—C41.351 (2)C12—C131.392 (2)
N1—C111.425 (2)C12—H120.9500
N1—H710.83 (2)C13—C141.388 (2)
C1—C21.485 (2)C13—H130.9500
C2—C51.319 (2)C14—C151.382 (3)
C2—C31.497 (2)C15—C161.389 (3)
C3—C41.523 (2)C15—H150.9500
C3—H3A0.9900C16—H160.9500
C1—O1—H1109.5C2—C5—H5B120.0
C4—N1—C11123.75 (14)H5A—C5—H5B120.0
C4—N1—H71117.5 (16)C12—C11—C16119.74 (15)
C11—N1—H71117.8 (16)C12—C11—N1121.60 (15)
O2—C1—O1123.55 (16)C16—C11—N1118.65 (15)
O2—C1—C2120.76 (15)C11—C12—C13120.12 (16)
O1—C1—C2115.69 (15)C11—C12—H12119.9
C5—C2—C1120.52 (16)C13—C12—H12119.9
C5—C2—C3123.74 (16)C14—C13—C12119.52 (16)
C1—C2—C3115.70 (14)C14—C13—H13120.2
C2—C3—C4112.22 (13)C12—C13—H13120.2
C2—C3—H3A109.2C15—C14—C13120.72 (16)
C4—C3—H3A109.2C15—C14—I1120.15 (13)
C2—C3—H3B109.2C13—C14—I1119.13 (13)
C4—C3—H3B109.2C14—C15—C16119.43 (16)
H3A—C3—H3B107.9C14—C15—H15120.3
O3—C4—N1123.00 (15)C16—C15—H15120.3
O3—C4—C3121.66 (15)C11—C16—C15120.43 (17)
N1—C4—C3115.28 (14)C11—C16—H16119.8
C2—C5—H5A120.0C15—C16—H16119.8
O2—C1—C2—C5168.65 (18)C4—N1—C11—C16131.82 (18)
O1—C1—C2—C511.0 (2)C16—C11—C12—C132.0 (3)
O2—C1—C2—C39.2 (2)N1—C11—C12—C13179.01 (16)
O1—C1—C2—C3171.13 (14)C11—C12—C13—C140.7 (3)
C5—C2—C3—C4108.2 (2)C12—C13—C14—C151.0 (3)
C1—C2—C3—C474.03 (18)C12—C13—C14—I1178.29 (14)
C11—N1—C4—O37.6 (3)C13—C14—C15—C161.4 (3)
C11—N1—C4—C3169.68 (15)I1—C14—C15—C16177.91 (14)
C2—C3—C4—O325.0 (2)C12—C11—C16—C151.6 (3)
C2—C3—C4—N1157.71 (14)N1—C11—C16—C15179.35 (17)
C4—N1—C11—C1249.1 (2)C14—C15—C16—C110.1 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O2i0.841.832.6597 (19)170
N1—H71···O3ii0.83 (2)2.10 (2)2.8963 (18)161 (2)
C3—H3B···O3ii0.992.513.266 (2)134
Symmetry codes: (i) x+1, y, z+1; (ii) x, y+1, z.

Experimental details

Crystal data
Chemical formulaC11H10INO3
Mr331.10
Crystal system, space groupMonoclinic, P21/c
Temperature (K)200
a, b, c (Å)23.1111 (6), 4.7863 (1), 10.4262 (2)
β (°) 97.071 (1)
V3)1144.54 (4)
Z4
Radiation typeMo Kα
µ (mm1)2.79
Crystal size (mm)0.29 × 0.16 × 0.10
Data collection
DiffractometerBruker APEXII CCD
Absorption correctionMulti-scan
(SADABS; Bruker, 2008)
Tmin, Tmax0.503, 0.776
No. of measured, independent and
observed [I > 2σ(I)] reflections
12435, 2839, 2612
Rint0.015
(sin θ/λ)max1)0.667
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.018, 0.047, 1.06
No. of reflections2839
No. of parameters150
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.73, 0.61

Computer programs: APEX2 (Bruker, 2010), SAINT (Bruker, 2010), SHELXS97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 2012) and Mercury (Macrae et al., 2008), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O2i0.841.832.6597 (19)170
N1—H71···O3ii0.83 (2)2.10 (2)2.8963 (18)161 (2)
C3—H3B···O3ii0.992.513.266 (2)134
Symmetry codes: (i) x+1, y, z+1; (ii) x, y+1, z.
 

Acknowledgements

BN thanks the UGC for financial assistance through a BSR one-time grant for the purchase of chemicals. PSN thanks Mangalore University for research facilities and the DST–PURSE for financial assistance.

References

First citationBernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573.  CrossRef CAS Web of Science Google Scholar
First citationBruker (2008). SADABS. Bruker Inc., Madison, Wisconsin, USA.  Google Scholar
First citationBruker (2010). APEX2 and SAINT. Bruker AXS Inc., Madison, USA.  Google Scholar
First citationEtter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256–262.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationFarrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationHanoon, H. D. (2011). Nat. J. Chem. 41, 77–89.  Google Scholar
First citationKatla, S., Pothana, P., Gubba, B. & Manda, S. (2011). Der Chem. Sin. 2, 47–53.  CAS Google Scholar
First citationMacrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
First citationOishi, T. (1980). Polym. J. 12, 719–727.  CrossRef CAS Web of Science Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationShetgiri, N. P. & Nayak, B. K. (2005). Indian J. Chem. Sect. B, 44, 1933–1936.  Google Scholar
First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationUrzua, M., Opazo, A., Gargallo, L. & Radic, D. (1998). Polym. Bull. 40, 63–67.  CAS 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