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Acta Crystallogr Sect E Struct Rep Online. 2010 May 1; 66(Pt 5): o1227–o1228.
Published online 2010 April 30. doi:  10.1107/S1600536810014923
PMCID: PMC2979134

(E)-1-[(2-Amino-5-nitro­phen­yl)iminio­meth­yl]naphthalen-2-olate

Abstract

The title Schiff base compound, C17H13N3O3, crystallizes in a zwitterionic form and exists in a trans configuration about the C=N bond. The mol­ecule is slightly twisted, the dihedral angle between the benzene ring and naphthalene ring system being 10.80 (9)°. The nitro group is twisted relative to the plane of the benzene ring [dihedral angle = 8.88 (12)°]. Bifurcated intra­molecular N—H(...)N and N—H(...)O hydrogen bonds formed between iminium groups and amine N atoms and naphthalen-2-olate O atoms generate S(5) and S(6) ring motifs, respectively. In the crystal, neighbouring zwitterions are linked through weak C—H(...)O inter­actions, giving rise to screw chains along [010]. Mol­ecules in these chains are linked to those of an adjacent chains through N—H(...)O hydrogen bonds and weak C—H(...)O inter­actions, forming sheets parallel to the ac plane. O(...)C [2.895 (3) Å] short contacts and π–π inter­actions [centroid–centroid distance = 3.8249 (19) Å] are also observed.

Related literature

For bond-length data, see: Allen et al. (1987 [triangle]). For hydrogen-bond motifs, see: Bernstein et al. (1995 [triangle]). For background to Schiff bases and their applications, see: Eltayeb et al. (2007 [triangle]; 2008 [triangle]); Dao et al. (2000 [triangle]); Kagkelari et al. (2009 [triangle]); Karthikeyan et al. (2006 [triangle]); Sondhi et al. (2006 [triangle]); Sriram et al. (2006 [triangle]). For related structures, see: Eltayeb et al. (2009 [triangle]; 2010 [triangle]). For the stability of the temperature controller used in the data collection, see Cosier & Glazer, (1986 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-66-o1227-scheme1.jpg

Experimental

Crystal data

  • C17H13N3O3
  • M r = 307.30
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-o1227-efi1.jpg
  • a = 10.369 (4) Å
  • b = 4.6442 (18) Å
  • c = 28.539 (9) Å
  • β = 103.548 (12)°
  • V = 1336.1 (8) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.11 mm−1
  • T = 100 K
  • 0.48 × 0.10 × 0.04 mm

Data collection

  • Bruker APEXII DUO CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2009 [triangle]) T min = 0.950, T max = 0.996
  • 14018 measured reflections
  • 3887 independent reflections
  • 2341 reflections with I > 2σ(I)
  • R int = 0.057

Refinement

  • R[F 2 > 2σ(F 2)] = 0.057
  • wR(F 2) = 0.151
  • S = 1.02
  • 3887 reflections
  • 220 parameters
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.36 e Å−3
  • Δρmin = −0.30 e Å−3

Data collection: APEX2 (Bruker, 2009 [triangle]); cell refinement: SAINT (Bruker, 2009 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810014923/sj2769sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810014923/sj2769Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

The authors thank the Malaysian Government, the Ministry of Science, Technology and Innovation (MOSTI) and Universiti Sains Malaysia for the RU research grants (1001/PKIMIA/815002 and 1001/PKIMIA/811120). AMF thanks the Libyan Government for providing a scholarship and Dr Naser Eltaher Eltayeb for his useful suggestions. The authors also thank the Malaysian Government and Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012.

supplementary crystallographic information

Comment

Schiff base ligands are members of an important class of compounds, possessing a wide spectrum of biological and pharmacological activities such as antibacterial and antifungal (Karthikeyan et al., 2006), anticancer (Dao et al., 2000), anti-HIV (Sriram et al., 2006), activities. Apart of these activities they have also been used as ligands to study coordination chemistry (Kagkelari et al., 2009). As part of our ongoing research on the synthesis of Schiff base ligands and their complexes (Eltayeb et al., 2007; 2008; 2009; 2010), the title compound (I) was synthesized and its crystal structure was determined. The title Schiff base ligand in neutral form was tested for anti-inflammatory, analgesic and kinase inhibition activities and showed moderate anti-inflammatory and analgesic activities (Sondhi et al., 2006).

The molecule of (I) (Fig. 1), C13H9BrNO2, crystallizes in a zwitterionic form with cationic iminium and anionic enolate, and exists in a trans configuration about the C═N bond [1.315 (3) Å] and the torsion angle C1–N1–C7–C8 = 175.18 (19)°. The naphthalene ring system [C8–C17] is planar with the r.m.s. 0.0069 (2) Å. The molecule is twisted with the dihedral angle between the benzene and naphthalene rings being 10.80 (9)°. The nitro group is twisted relative to the plane of the C8–C13 benzene ring with an interplanar angle of 8.88 (12)° and torsion angles O2–N3–C5–C4 = 8.4 (3) and O3–N3–C5–C4 = -171.70 (19)°. Bifurcated intramolecular N1—H1N1···N2 and N1—H1N1···O1 hydrogen bonds (Fig.1) which formed between the NH+ and amino N atom and to the naphthalen-2-olate O- generates an S(5) and S(6) ring motifs, respectively (Bernstein et al., 1995). The bond distances are in normal ranges (Allen et al., 1987) and comparable with the related structures (Eltayeb et al., 2009; 2010).

In the crystal packing, neighbouring zwitterions are linked through weak C—H···O interactions (Table 1) giving rise to screw chains along the [010] direction (Fig. 2). Molecules in a chain are linked to those of adjacent chains through N—H···O(naphthalen-2-olate) hydrogen bonds and weak C—H···O(nitro) interactions (Table 1, Fig. 3), forming sheets parallel to the ac plane. O···C [2.895 (3) Å] short contacts and π–π interactions with centroid···centroid distances of 3.8249 (19) Å are also observed.

Experimental

The title compound was synthesized by adding 2-hydroxy-1-naphthaldehyde (0.688 g, 4 mmol) to the solution of 4-nitrobenzene-1,2-diamine (0.306 g, 2 mmol) in ethanol (30 ml). The mixture was refluxed with stirring for 3 hrs. The resultant solid was obtained and then filtered and washed with ethanol. Red plate-shaped single crystals of the title compound suitable for x-ray structure determination were obtained from acetone by slow evaporation at room temperature after several days.

Refinement

Amine and iminium H atoms were located from the difference maps and were refined isotropically. The remaining H atoms were placed in calculated positions with d(C—H) = 0.93 Å for aromatic and CH atoms and the Uiso values were constrained to be 1.2Ueq of the carrier atoms. The highest residual electron density peak is located at 0.70 Å from H4A and the deepest hole is located at 0.65 Å from C4.

Figures

Fig. 1.
The molecular structure of the title compound, with 50° probability displacement ellipsoids and the atom-numbering scheme. Intramolecular hydrogen bonds are shown as dashed lines." is correct.
Fig. 2.
The crystal packing of the title compound viewed down the a, showing screw chains running along the b axis. Hydrogen bonds are shown as dashed lines.
Fig. 3.
The crystal packing of the title compound viewed down the b, showing sheet parallel to the ac plane. Hydrogen bonds are shown as dashed lines.

Crystal data

C17H13N3O3F(000) = 640
Mr = 307.30Dx = 1.528 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 3887 reflections
a = 10.369 (4) Åθ = 1.5–30.0°
b = 4.6442 (18) ŵ = 0.11 mm1
c = 28.539 (9) ÅT = 100 K
β = 103.548 (12)°Plate, red
V = 1336.1 (8) Å30.48 × 0.10 × 0.04 mm
Z = 4

Data collection

Bruker APEXII DUO CCD area-detector diffractometer3887 independent reflections
Radiation source: sealed tube2341 reflections with I > 2σ(I)
graphiteRint = 0.057
[var phi] and ω scansθmax = 30.0°, θmin = 1.5°
Absorption correction: multi-scan (SADABS; Bruker, 2009)h = −14→13
Tmin = 0.950, Tmax = 0.996k = −6→6
14018 measured reflectionsl = −39→40

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.057Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.151H atoms treated by a mixture of independent and constrained refinement
S = 1.01w = 1/[σ2(Fo2) + (0.059P)2 + 0.6347P] where P = (Fo2 + 2Fc2)/3
3887 reflections(Δ/σ)max = 0.001
220 parametersΔρmax = 0.36 e Å3
0 restraintsΔρmin = −0.30 e Å3

Special details

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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. 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)

xyzUiso*/Ueq
O10.82332 (14)−0.0589 (3)0.96873 (5)0.0254 (4)
O21.22099 (15)−0.6304 (4)0.76236 (5)0.0338 (4)
O31.09865 (15)−0.2495 (4)0.74798 (5)0.0317 (4)
N10.92876 (16)−0.1176 (4)0.89879 (5)0.0198 (4)
H1N10.911 (3)−0.151 (6)0.9315 (10)0.053 (8)*
N21.08296 (18)−0.4892 (5)0.96268 (6)0.0250 (4)
H1N21.068 (2)−0.318 (6)0.9746 (9)0.038 (7)*
H2N21.134 (2)−0.630 (6)0.9828 (9)0.036 (7)*
N31.15214 (17)−0.4461 (4)0.77485 (6)0.0254 (4)
C11.02284 (18)−0.2851 (5)0.88271 (6)0.0189 (4)
C21.09971 (19)−0.4753 (5)0.91675 (6)0.0200 (4)
C31.1889 (2)−0.6596 (5)0.90188 (7)0.0231 (5)
H3A1.2383−0.78890.92380.028*
C41.2048 (2)−0.6533 (5)0.85552 (7)0.0234 (5)
H4A1.2636−0.77830.84580.028*
C51.13185 (19)−0.4580 (5)0.82357 (6)0.0215 (4)
C61.04003 (19)−0.2757 (5)0.83600 (6)0.0216 (4)
H6A0.9907−0.14920.81350.026*
C70.84656 (19)0.0765 (5)0.87499 (6)0.0196 (4)
H7A0.85140.12690.84390.023*
C80.75161 (19)0.2092 (5)0.89575 (6)0.0194 (4)
C90.7424 (2)0.1231 (5)0.94325 (6)0.0211 (4)
C100.6390 (2)0.2452 (5)0.96265 (6)0.0243 (5)
H10A0.63000.18720.99290.029*
C110.5547 (2)0.4420 (5)0.93792 (7)0.0242 (5)
H11A0.48940.51730.95180.029*
C120.56177 (19)0.5396 (5)0.89118 (6)0.0208 (4)
C130.4720 (2)0.7454 (5)0.86662 (7)0.0239 (5)
H13A0.40880.82220.88140.029*
C140.4757 (2)0.8357 (5)0.82110 (7)0.0252 (5)
H14A0.41480.97010.80490.030*
C150.5722 (2)0.7223 (5)0.79976 (6)0.0230 (5)
H15A0.57580.78340.76910.028*
C160.66212 (19)0.5223 (5)0.82295 (6)0.0214 (4)
H16A0.72580.45150.80780.026*
C170.65970 (19)0.4222 (5)0.86945 (6)0.0188 (4)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0339 (8)0.0264 (9)0.0168 (6)0.0063 (7)0.0075 (6)0.0041 (6)
O20.0391 (9)0.0402 (11)0.0257 (7)0.0115 (8)0.0148 (7)−0.0053 (7)
O30.0429 (9)0.0331 (10)0.0218 (7)0.0053 (8)0.0127 (6)0.0051 (7)
N10.0263 (8)0.0187 (10)0.0156 (7)−0.0005 (7)0.0069 (6)−0.0004 (7)
N20.0335 (10)0.0246 (11)0.0176 (8)0.0047 (9)0.0075 (7)0.0008 (8)
N30.0306 (9)0.0270 (11)0.0204 (8)0.0009 (8)0.0097 (7)−0.0028 (7)
C10.0249 (9)0.0159 (11)0.0177 (8)−0.0038 (8)0.0085 (7)−0.0033 (7)
C20.0245 (9)0.0185 (12)0.0177 (8)−0.0038 (9)0.0063 (7)−0.0012 (8)
C30.0257 (10)0.0203 (12)0.0237 (9)0.0012 (9)0.0065 (8)0.0008 (8)
C40.0260 (10)0.0207 (12)0.0249 (9)0.0014 (9)0.0086 (8)−0.0032 (8)
C50.0250 (9)0.0247 (13)0.0160 (8)−0.0022 (9)0.0075 (7)−0.0033 (8)
C60.0268 (9)0.0208 (12)0.0173 (8)−0.0022 (9)0.0053 (7)−0.0005 (8)
C70.0262 (9)0.0171 (11)0.0155 (8)−0.0028 (8)0.0049 (7)−0.0001 (7)
C80.0250 (9)0.0178 (11)0.0152 (8)−0.0017 (8)0.0046 (7)−0.0003 (8)
C90.0284 (10)0.0182 (11)0.0165 (8)−0.0003 (9)0.0045 (7)0.0000 (8)
C100.0343 (11)0.0246 (13)0.0158 (8)0.0029 (10)0.0098 (8)0.0029 (8)
C110.0289 (10)0.0241 (13)0.0211 (9)0.0016 (9)0.0093 (8)−0.0007 (8)
C120.0249 (9)0.0190 (12)0.0182 (8)−0.0031 (9)0.0047 (7)−0.0005 (8)
C130.0270 (10)0.0233 (13)0.0218 (9)0.0025 (9)0.0063 (8)0.0000 (8)
C140.0300 (10)0.0233 (13)0.0212 (9)−0.0001 (9)0.0035 (8)0.0021 (8)
C150.0299 (10)0.0232 (12)0.0155 (8)−0.0023 (9)0.0046 (7)0.0008 (8)
C160.0272 (10)0.0205 (12)0.0173 (8)−0.0035 (9)0.0069 (7)−0.0011 (8)
C170.0238 (9)0.0162 (11)0.0160 (8)−0.0039 (8)0.0039 (7)−0.0008 (7)

Geometric parameters (Å, °)

O1—C91.289 (2)C7—C81.405 (3)
O2—N31.220 (2)C7—H7A0.9300
O3—N31.237 (2)C8—C91.438 (3)
N1—C71.315 (3)C8—C171.454 (3)
N1—C11.406 (2)C9—C101.434 (3)
N1—H1N11.00 (3)C10—C111.344 (3)
N2—C21.364 (2)C10—H10A0.9300
N2—H1N20.89 (3)C11—C121.427 (3)
N2—H2N20.94 (3)C11—H11A0.9300
N3—C51.455 (2)C12—C131.402 (3)
C1—C61.386 (2)C12—C171.417 (3)
C1—C21.413 (3)C13—C141.374 (3)
C2—C31.397 (3)C13—H13A0.9300
C3—C41.371 (3)C14—C151.391 (3)
C3—H3A0.9300C14—H14A0.9300
C4—C51.380 (3)C15—C161.372 (3)
C4—H4A0.9300C15—H15A0.9300
C5—C61.381 (3)C16—C171.412 (3)
C6—H6A0.9300C16—H16A0.9300
C7—N1—C1128.76 (16)C7—C8—C9118.92 (18)
C7—N1—H1N1110.5 (16)C7—C8—C17121.33 (16)
C1—N1—H1N1120.5 (16)C9—C8—C17119.71 (17)
C2—N2—H1N2113.4 (17)O1—C9—C10119.21 (17)
C2—N2—H2N2116.1 (15)O1—C9—C8122.43 (18)
H1N2—N2—H2N2120 (2)C10—C9—C8118.36 (18)
O2—N3—O3123.00 (17)C11—C10—C9121.25 (17)
O2—N3—C5118.54 (18)C11—C10—H10A119.4
O3—N3—C5118.46 (17)C9—C10—H10A119.4
C6—C1—N1123.48 (18)C10—C11—C12122.52 (19)
C6—C1—C2120.14 (18)C10—C11—H11A118.7
N1—C1—C2116.36 (16)C12—C11—H11A118.7
N2—C2—C3120.35 (19)C13—C12—C17120.24 (17)
N2—C2—C1120.83 (19)C13—C12—C11120.69 (18)
C3—C2—C1118.74 (17)C17—C12—C11119.05 (18)
C4—C3—C2121.19 (19)C14—C13—C12121.21 (19)
C4—C3—H3A119.4C14—C13—H13A119.4
C2—C3—H3A119.4C12—C13—H13A119.4
C3—C4—C5118.71 (19)C13—C14—C15118.7 (2)
C3—C4—H4A120.6C13—C14—H14A120.6
C5—C4—H4A120.6C15—C14—H14A120.6
C4—C5—C6122.52 (17)C16—C15—C14121.52 (18)
C4—C5—N3118.49 (18)C16—C15—H15A119.2
C6—C5—N3118.99 (18)C14—C15—H15A119.2
C5—C6—C1118.63 (19)C15—C16—C17121.11 (19)
C5—C6—H6A120.7C15—C16—H16A119.4
C1—C6—H6A120.7C17—C16—H16A119.4
N1—C7—C8121.09 (17)C16—C17—C12117.18 (18)
N1—C7—H7A119.5C16—C17—C8123.74 (18)
C8—C7—H7A119.5C12—C17—C8119.08 (16)
C7—N1—C1—C6−2.5 (3)C17—C8—C9—O1−178.14 (19)
C7—N1—C1—C2179.1 (2)C7—C8—C9—C10−175.65 (19)
C6—C1—C2—N2−179.3 (2)C17—C8—C9—C102.0 (3)
N1—C1—C2—N2−0.8 (3)O1—C9—C10—C11178.1 (2)
C6—C1—C2—C3−2.4 (3)C8—C9—C10—C11−2.0 (3)
N1—C1—C2—C3176.07 (18)C9—C10—C11—C120.5 (3)
N2—C2—C3—C4178.5 (2)C10—C11—C12—C13−179.9 (2)
C1—C2—C3—C41.6 (3)C10—C11—C12—C171.1 (3)
C2—C3—C4—C50.8 (3)C17—C12—C13—C140.6 (3)
C3—C4—C5—C6−2.4 (3)C11—C12—C13—C14−178.3 (2)
C3—C4—C5—N3178.11 (19)C12—C13—C14—C15−1.0 (3)
O2—N3—C5—C48.4 (3)C13—C14—C15—C160.5 (3)
O3—N3—C5—C4−171.70 (19)C14—C15—C16—C170.4 (3)
O2—N3—C5—C6−171.2 (2)C15—C16—C17—C12−0.8 (3)
O3—N3—C5—C68.8 (3)C15—C16—C17—C8179.5 (2)
C4—C5—C6—C11.5 (3)C13—C12—C17—C160.3 (3)
N3—C5—C6—C1−178.97 (19)C11—C12—C17—C16179.27 (19)
N1—C1—C6—C5−177.46 (19)C13—C12—C17—C8179.96 (19)
C2—C1—C6—C50.9 (3)C11—C12—C17—C8−1.0 (3)
C1—N1—C7—C8175.18 (19)C7—C8—C17—C16−3.2 (3)
N1—C7—C8—C9−1.9 (3)C9—C8—C17—C16179.21 (19)
N1—C7—C8—C17−179.45 (19)C7—C8—C17—C12177.07 (19)
C7—C8—C9—O14.3 (3)C9—C8—C17—C12−0.5 (3)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
N1—H1N1···O11.01 (3)1.61 (3)2.505 (2)146 (3)
N1—H1N1···N21.01 (3)2.39 (3)2.737 (3)100 (2)
N2—H1N2···O1i0.89 (3)2.47 (3)3.219 (3)142.0 (19)
N2—H2N2···O1ii0.95 (3)1.98 (3)2.879 (3)158.6 (19)
C6—H6A···O3iii0.932.573.489 (3)168
C15—H15A···O2iv0.932.513.161 (3)127

Symmetry codes: (i) −x+2, −y, −z+2; (ii) −x+2, −y−1, −z+2; (iii) −x+2, y+1/2, −z+3/2; (iv) −x+2, y+3/2, −z+3/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SJ2769).

References

  • Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.
  • Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl 34, 1555–1573.
  • Bruker (2009). APEX2, SAINT and SADABS Bruker AXS Inc., Madison, Wisconsin, USA.
  • Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst.19, 105–107.
  • Dao, V.-T., Gaspard, C., Mayer, M., Werner, G. H., Nguyen, S. N. & Michelot, R. J. (2000). Eur. J. Med. Chem 35, 805–813. [PubMed]
  • Eltayeb, N. E., Teoh, S. G., Chantrapromma, S. & Fun, H.-K. (2010). Acta Cryst. E66, o934–o935. [PMC free article] [PubMed]
  • Eltayeb, N. E., Teoh, S. G., Chantrapromma, S., Fun, H.-K. & Adnan, R. (2008). Acta Cryst. E64, m570–m571. [PMC free article] [PubMed]
  • Eltayeb, N. E., Teoh, S. G., Chantrapromma, S., Fun, H.-K. & Ibrahim, K. (2007). Acta Cryst. E63, m1672–m1673.
  • Eltayeb, N. E., Teoh, S. G., Yeap, C. S., Fun, H.-K. & Adnan, R. (2009). Acta Cryst. E65, o2065–o2066. [PMC free article] [PubMed]
  • Kagkelari, A., Papaefstahiou, G. S., Raptopoulou, C. P. & Zafiropoulos, T. F. (2009). Polyhedron, 28, 3279–3283.
  • Karthikeyan, M. S., Prasad, D. J., Poojary, B., Bhat, K. S., Holla, B. S. & Kumari, N. S. (2006). Bioorg. Med. Chem 14, 7482–7489. [PubMed]
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Sondhi, S. M., Singh, N., Kumar, A., Lozach, O. & Meijer, L. (2006). Bioorg. Med. Chem. 14, 3758–3765. [PubMed]
  • Spek, A. L. (2009). Acta Cryst D65, 148–155. [PMC free article] [PubMed]
  • Sriram, D., Yogeeswari, P., Myneedu, N. S. & Saraswat, V. (2006). Bioorg. Med. Chem. Lett 16, 2127–2129. [PubMed]

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