PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of actaeInternational Union of Crystallographysearchopen accessarticle submissionjournal home pagethis article
 
Acta Crystallogr Sect E Struct Rep Online. 2009 January 1; 65(Pt 1): o51.
Published online 2008 December 10. doi:  10.1107/S1600536808040932
PMCID: PMC2967965

Ethyl {6-[6-(ethoxy­carbon­yl)picolin­amido­carbon­yl]picolinamido­carbon­yl}picolinate

Abstract

The title mol­ecule, C25H21N5O8, adopts a helical conformation, which is stabilized by two intra­molecular bifurcated N—H(...)(N,N) hydrogen bonds.

Related literature

For a review on aromatic oligoamides (AOAs), see, for example: Huc (2004 [triangle]). For related compounds, see: Li et al. (2008 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-00o51-scheme1.jpg

Experimental

Crystal data

  • C25H21N5O8
  • M r = 519.47
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-00o51-efi1.jpg
  • a = 7.4952 (8) Å
  • b = 19.998 (2) Å
  • c = 15.9966 (17) Å
  • β = 96.376 (1)°
  • V = 2382.8 (4) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.11 mm−1
  • T = 113 (2) K
  • 0.32 × 0.22 × 0.18 mm

Data collection

  • Rigaku Saturn diffractometer
  • Absorption correction: multi-scan (CrystalcClear; Rigaku, 1999 [triangle]) T min = 0.966, T max = 0.980
  • 30537 measured reflections
  • 6101 independent reflections
  • 5457 reflections with I > 2σ(I)
  • R int = 0.025

Refinement

  • R[F 2 > 2σ(F 2)] = 0.037
  • wR(F 2) = 0.096
  • S = 1.08
  • 6101 reflections
  • 354 parameters
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.32 e Å−3
  • Δρmin = −0.17 e Å−3

Data collection: CrystalClear (Rigaku, 1999 [triangle]); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: CrystalStructure (Rigaku, 1999 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808040932/hb2864sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808040932/hb2864Isup2.hkl

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

Acknowledgments

We thank the NSFC (Nos. 50221201, 20872145, 20733006), the Chinese Academy of Sciences and the National Research Fund for Fundamental Key Project 973 (2006CB806200, 2007CB936401) for support.

supplementary crystallographic information

Comment

The stucture of the title compound is shown in Fig. 1. Dimensions are available in the archived CIF. The hydrogen bonds are listed in Table 1. For background, see for example: Huc (2004). For related compounds, see: Li et al. (2008).

Experimental

The title compound was obtained from 2-ethoxycarbonyl- 6-pyridinoyl amide and 2,6-pyridinoyl dichloride and recrystallised from DMF/ethyl ether to yield colourless prisms of (I).

Refinement

The N-bound hydrogen atoms were located in a difference map and freely refined. The C-bound hydrogen atoms were geometrically placed (C—H = 0.95–0.99Å) and refined as riding with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C).

Figures

Fig. 1.
The molecular structure of (I) showing 50% displacement ellipsoids for the non-hydrogen atoms. The hydrogen bonds are shown as double-dashed lines.
Fig. 2.
The formation of the title compound.

Crystal data

C25H21N5O8F(000) = 1080
Mr = 519.47Dx = 1.448 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71070 Å
Hall symbol: -P 2ybcCell parameters from 6439 reflections
a = 7.4952 (8) Åθ = 2.6–26.0°
b = 19.998 (2) ŵ = 0.11 mm1
c = 15.9966 (17) ÅT = 113 K
β = 96.376 (1)°Prism, colorless
V = 2382.8 (4) Å30.32 × 0.22 × 0.18 mm
Z = 4

Data collection

Rigaku Saturn diffractometer6101 independent reflections
Radiation source: rotating anode5457 reflections with I > 2σ(I)
confocalRint = 0.025
Detector resolution: 7.31 pixels mm-1θmax = 28.7°, θmin = 2.4°
ω scansh = −10→10
Absorption correction: multi-scan (CrystalcClear; Rigaku, 1999)k = −27→24
Tmin = 0.966, Tmax = 0.980l = −21→21
30537 measured reflections

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)] = 0.037Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.096H atoms treated by a mixture of independent and constrained refinement
S = 1.08w = 1/[σ2(Fo2) + (0.0481P)2 + 0.4996P] where P = (Fo2 + 2Fc2)/3
6101 reflections(Δ/σ)max = 0.001
354 parametersΔρmax = 0.32 e Å3
0 restraintsΔρmin = −0.17 e Å3

Special details

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)

xyzUiso*/Ueq
O1−0.13320 (11)0.87694 (4)0.72665 (5)0.02977 (17)
O20.06124 (11)0.85871 (4)0.63149 (5)0.02910 (17)
O3−0.16781 (12)0.59423 (4)0.88294 (6)0.0395 (2)
O4−0.33384 (11)0.65393 (4)1.02334 (5)0.03521 (19)
O5−0.24510 (13)0.99672 (4)0.94666 (5)0.0397 (2)
O60.08420 (13)1.00415 (4)0.86648 (5)0.0391 (2)
O70.21781 (10)0.70449 (4)0.93765 (4)0.02615 (16)
O80.37042 (9)0.67410 (4)0.82982 (4)0.02587 (16)
N1−0.10247 (10)0.74283 (4)0.76977 (5)0.02135 (16)
N2−0.21026 (12)0.70511 (4)0.91366 (5)0.02446 (18)
N3−0.25843 (11)0.82284 (4)0.97648 (5)0.02253 (17)
N4−0.04508 (12)0.91296 (4)0.92339 (5)0.02641 (18)
N50.20551 (11)0.83332 (4)0.87730 (5)0.02099 (16)
C1−0.04508 (13)0.83975 (5)0.68831 (6)0.02336 (19)
C2−0.03851 (12)0.76501 (5)0.70001 (6)0.02167 (19)
C30.02896 (13)0.72245 (5)0.64172 (6)0.0245 (2)
H30.07640.74000.59360.029*
C40.02507 (13)0.65399 (5)0.65576 (6)0.0264 (2)
H4A0.06570.62370.61620.032*
C5−0.03894 (13)0.63047 (5)0.72829 (7)0.0262 (2)
H5−0.04190.58390.73980.031*
C6−0.09874 (12)0.67674 (5)0.78370 (6)0.02280 (19)
C7−0.16141 (13)0.65290 (5)0.86502 (7)0.0260 (2)
C8−0.29462 (13)0.70359 (5)0.98611 (6)0.0248 (2)
C9−0.34013 (13)0.77315 (5)1.01301 (6)0.0241 (2)
C10−0.46393 (14)0.78407 (7)1.07012 (7)0.0334 (2)
H10−0.51800.74781.09610.040*
C11−0.50571 (15)0.84953 (7)1.08782 (8)0.0400 (3)
H11−0.59040.85881.12630.048*
C12−0.42408 (15)0.90164 (6)1.04950 (7)0.0353 (3)
H12−0.45300.94681.06030.042*
C13−0.29831 (14)0.88586 (5)0.99470 (6)0.0263 (2)
C14−0.19693 (15)0.93888 (5)0.95273 (6)0.0287 (2)
C150.08115 (15)0.94475 (5)0.88163 (6)0.0272 (2)
C160.22015 (13)0.89727 (5)0.85479 (6)0.0240 (2)
C170.35075 (15)0.92050 (6)0.80694 (7)0.0318 (2)
H170.35870.96670.79390.038*
C180.46885 (15)0.87489 (6)0.77877 (8)0.0350 (3)
H180.56030.88920.74620.042*
C190.45178 (14)0.80778 (6)0.79891 (7)0.0290 (2)
H190.52860.77510.77880.035*
C200.31961 (12)0.78940 (5)0.84913 (6)0.02153 (19)
C210.29545 (12)0.71868 (5)0.87815 (6)0.02146 (19)
C220.06263 (18)0.92999 (5)0.61175 (7)0.0342 (2)
H22A0.08270.95680.66400.041*
H22B−0.05320.94350.58060.041*
C230.2126 (2)0.94046 (6)0.55884 (9)0.0482 (4)
H23A0.32670.92820.59120.072*
H23B0.21630.98760.54230.072*
H23C0.19310.91240.50840.072*
C240.35652 (15)0.60428 (5)0.85650 (7)0.0275 (2)
H24A0.23150.59410.86660.033*
H24B0.43560.59650.90940.033*
C250.41238 (17)0.56010 (6)0.78771 (7)0.0352 (2)
H25A0.32900.56620.73660.053*
H25B0.41040.51330.80560.053*
H25C0.53410.57210.77620.053*
H4−0.0313 (18)0.8692 (7)0.9284 (8)0.036 (4)*
H2−0.1908 (19)0.7449 (8)0.8932 (9)0.040 (4)*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0356 (4)0.0277 (4)0.0269 (4)0.0077 (3)0.0077 (3)−0.0011 (3)
O20.0378 (4)0.0242 (4)0.0268 (4)0.0026 (3)0.0104 (3)0.0007 (3)
O30.0507 (5)0.0201 (4)0.0503 (5)−0.0036 (3)0.0176 (4)0.0003 (3)
O40.0350 (4)0.0360 (4)0.0355 (4)−0.0062 (3)0.0075 (3)0.0099 (3)
O50.0549 (5)0.0247 (4)0.0386 (5)0.0185 (4)0.0005 (4)−0.0020 (3)
O60.0650 (6)0.0165 (4)0.0358 (4)−0.0003 (4)0.0059 (4)0.0058 (3)
O70.0308 (4)0.0222 (4)0.0266 (4)0.0031 (3)0.0085 (3)0.0035 (3)
O80.0267 (4)0.0239 (4)0.0280 (4)0.0045 (3)0.0076 (3)0.0009 (3)
N10.0193 (4)0.0215 (4)0.0231 (4)−0.0004 (3)0.0013 (3)−0.0035 (3)
N20.0272 (4)0.0203 (4)0.0269 (4)−0.0018 (3)0.0075 (3)0.0004 (3)
N30.0231 (4)0.0256 (4)0.0186 (4)0.0055 (3)0.0007 (3)−0.0008 (3)
N40.0374 (5)0.0147 (4)0.0277 (4)0.0050 (3)0.0059 (3)0.0009 (3)
N50.0218 (4)0.0188 (4)0.0218 (4)−0.0021 (3)−0.0004 (3)0.0022 (3)
C10.0249 (5)0.0267 (5)0.0179 (4)0.0022 (4)0.0001 (3)−0.0014 (3)
C20.0187 (4)0.0245 (5)0.0211 (4)0.0011 (3)−0.0011 (3)−0.0036 (3)
C30.0209 (4)0.0301 (5)0.0218 (4)0.0016 (4)0.0001 (3)−0.0058 (4)
C40.0223 (4)0.0286 (5)0.0278 (5)0.0021 (4)−0.0002 (4)−0.0109 (4)
C50.0234 (5)0.0220 (5)0.0325 (5)−0.0012 (4)0.0005 (4)−0.0084 (4)
C60.0194 (4)0.0218 (5)0.0269 (5)−0.0022 (3)0.0013 (3)−0.0053 (4)
C70.0241 (5)0.0208 (5)0.0334 (5)−0.0028 (4)0.0052 (4)−0.0024 (4)
C80.0197 (4)0.0309 (5)0.0239 (5)−0.0021 (4)0.0020 (3)0.0026 (4)
C90.0190 (4)0.0340 (5)0.0189 (4)0.0008 (4)0.0009 (3)−0.0006 (4)
C100.0233 (5)0.0522 (7)0.0254 (5)−0.0044 (5)0.0061 (4)−0.0067 (5)
C110.0255 (5)0.0603 (8)0.0357 (6)0.0018 (5)0.0099 (4)−0.0177 (6)
C120.0280 (5)0.0441 (7)0.0332 (6)0.0112 (5)0.0014 (4)−0.0141 (5)
C130.0260 (5)0.0299 (5)0.0218 (4)0.0099 (4)−0.0017 (4)−0.0048 (4)
C140.0375 (6)0.0245 (5)0.0231 (5)0.0103 (4)−0.0013 (4)−0.0029 (4)
C150.0412 (6)0.0179 (4)0.0219 (4)−0.0010 (4)0.0004 (4)0.0022 (3)
C160.0281 (5)0.0200 (5)0.0230 (4)−0.0040 (4)−0.0017 (4)0.0036 (3)
C170.0330 (5)0.0279 (5)0.0338 (5)−0.0085 (4)0.0005 (4)0.0108 (4)
C180.0250 (5)0.0423 (7)0.0383 (6)−0.0051 (4)0.0060 (4)0.0166 (5)
C190.0203 (4)0.0365 (6)0.0304 (5)0.0028 (4)0.0040 (4)0.0096 (4)
C200.0183 (4)0.0236 (5)0.0220 (4)0.0000 (3)−0.0007 (3)0.0037 (3)
C210.0180 (4)0.0229 (5)0.0229 (4)0.0024 (3)0.0001 (3)0.0015 (3)
C220.0510 (7)0.0238 (5)0.0287 (5)0.0041 (5)0.0082 (5)0.0031 (4)
C230.0808 (10)0.0273 (6)0.0419 (7)−0.0084 (6)0.0309 (7)−0.0045 (5)
C240.0320 (5)0.0221 (5)0.0288 (5)0.0063 (4)0.0056 (4)0.0017 (4)
C250.0420 (6)0.0298 (6)0.0350 (6)0.0093 (5)0.0095 (5)−0.0033 (4)

Geometric parameters (Å, °)

O1—C11.2064 (12)C8—C91.5063 (15)
O2—C11.3289 (12)C9—C101.3898 (14)
O2—C221.4603 (13)C10—C111.3825 (18)
O3—C71.2100 (13)C10—H100.9500
O4—C81.2109 (13)C11—C121.3854 (19)
O5—C141.2123 (13)C11—H110.9500
O6—C151.2131 (13)C12—C131.3930 (15)
O7—C211.2034 (12)C12—H120.9500
O8—C211.3434 (12)C13—C141.5052 (16)
O8—C241.4671 (12)C15—C161.5068 (15)
N1—C21.3382 (13)C16—C171.3880 (15)
N1—C61.3401 (13)C17—C181.3809 (17)
N2—C71.3760 (13)C17—H170.9500
N2—C81.3809 (13)C18—C191.3893 (16)
N2—H20.878 (15)C18—H180.9500
N3—C131.3348 (13)C19—C201.3924 (14)
N3—C91.3354 (13)C19—H190.9500
N4—C151.3732 (14)C20—C211.5057 (13)
N4—C141.3796 (14)C22—C231.4949 (18)
N4—H40.885 (14)C22—H22A0.9900
N5—C161.3364 (12)C22—H22B0.9900
N5—C201.3384 (13)C23—H23A0.9800
C1—C21.5064 (14)C23—H23B0.9800
C2—C31.3979 (13)C23—H23C0.9800
C3—C41.3882 (15)C24—C251.5064 (14)
C3—H30.9500C24—H24A0.9900
C4—C51.3859 (15)C24—H24B0.9900
C4—H4A0.9500C25—H25A0.9800
C5—C61.3895 (14)C25—H25B0.9800
C5—H50.9500C25—H25C0.9800
C6—C71.5086 (14)
C1—O2—C22116.47 (8)C12—C13—C14122.10 (10)
C21—O8—C24114.60 (8)O5—C14—N4125.50 (11)
C2—N1—C6117.56 (8)O5—C14—C13123.18 (10)
C7—N2—C8129.30 (9)N4—C14—C13111.32 (8)
C7—N2—H2114.2 (9)O6—C15—N4125.43 (11)
C8—N2—H2116.3 (9)O6—C15—C16122.08 (10)
C13—N3—C9118.83 (9)N4—C15—C16112.49 (8)
C15—N4—C14129.10 (9)N5—C16—C17123.57 (10)
C15—N4—H4115.0 (9)N5—C16—C15116.50 (9)
C14—N4—H4115.7 (9)C17—C16—C15119.90 (9)
C16—N5—C20117.56 (9)C18—C17—C16118.41 (10)
O1—C1—O2125.14 (10)C18—C17—H17120.8
O1—C1—C2124.11 (9)C16—C17—H17120.8
O2—C1—C2110.75 (8)C17—C18—C19118.91 (10)
N1—C2—C3122.96 (9)C17—C18—H18120.5
N1—C2—C1114.99 (8)C19—C18—H18120.5
C3—C2—C1122.04 (9)C18—C19—C20118.59 (10)
C4—C3—C2118.48 (10)C18—C19—H19120.7
C4—C3—H3120.8C20—C19—H19120.7
C2—C3—H3120.8N5—C20—C19122.90 (9)
C5—C4—C3119.04 (9)N5—C20—C21114.16 (8)
C5—C4—H4A120.5C19—C20—C21122.92 (9)
C3—C4—H4A120.5O7—C21—O8124.66 (9)
C4—C5—C6118.31 (10)O7—C21—C20123.41 (9)
C4—C5—H5120.8O8—C21—C20111.94 (8)
C6—C5—H5120.8O2—C22—C23106.44 (9)
N1—C6—C5123.57 (9)O2—C22—H22A110.4
N1—C6—C7116.89 (8)C23—C22—H22A110.4
C5—C6—C7119.53 (9)O2—C22—H22B110.4
O3—C7—N2125.58 (10)C23—C22—H22B110.4
O3—C7—C6122.35 (9)H22A—C22—H22B108.6
N2—C7—C6112.06 (8)C22—C23—H23A109.5
O4—C8—N2126.13 (10)C22—C23—H23B109.5
O4—C8—C9122.81 (9)H23A—C23—H23B109.5
N2—C8—C9111.02 (8)C22—C23—H23C109.5
N3—C9—C10122.87 (10)H23A—C23—H23C109.5
N3—C9—C8115.64 (8)H23B—C23—H23C109.5
C10—C9—C8121.45 (10)O8—C24—C25108.13 (8)
C11—C10—C9117.80 (11)O8—C24—H24A110.1
C11—C10—H10121.1C25—C24—H24A110.1
C9—C10—H10121.1O8—C24—H24B110.1
C10—C11—C12120.02 (10)C25—C24—H24B110.1
C10—C11—H11120.0H24A—C24—H24B108.4
C12—C11—H11120.0C24—C25—H25A109.5
C11—C12—C13118.10 (11)C24—C25—H25B109.5
C11—C12—H12121.0H25A—C25—H25B109.5
C13—C12—H12121.0C24—C25—H25C109.5
N3—C13—C12122.34 (11)H25A—C25—H25C109.5
N3—C13—C14115.55 (9)H25B—C25—H25C109.5
C22—O2—C1—O1−3.25 (15)C9—N3—C13—C12−0.98 (14)
C22—O2—C1—C2177.85 (8)C9—N3—C13—C14178.44 (8)
C6—N1—C2—C30.73 (13)C11—C12—C13—N31.89 (16)
C6—N1—C2—C1−179.54 (8)C11—C12—C13—C14−177.48 (10)
O1—C1—C2—N1−15.36 (14)C15—N4—C14—O5−0.58 (18)
O2—C1—C2—N1163.55 (8)C15—N4—C14—C13179.72 (9)
O1—C1—C2—C3164.37 (10)N3—C13—C14—O5162.22 (10)
O2—C1—C2—C3−16.71 (12)C12—C13—C14—O5−18.36 (16)
N1—C2—C3—C41.73 (14)N3—C13—C14—N4−18.07 (12)
C1—C2—C3—C4−177.98 (8)C12—C13—C14—N4161.35 (9)
C2—C3—C4—C5−2.40 (14)C14—N4—C15—O63.77 (18)
C3—C4—C5—C60.72 (14)C14—N4—C15—C16−175.83 (9)
C2—N1—C6—C5−2.58 (14)C20—N5—C16—C17−2.57 (14)
C2—N1—C6—C7176.59 (8)C20—N5—C16—C15175.38 (8)
C4—C5—C6—N11.87 (15)O6—C15—C16—N5178.10 (10)
C4—C5—C6—C7−177.27 (9)N4—C15—C16—N5−2.29 (12)
C8—N2—C7—O3−8.40 (18)O6—C15—C16—C17−3.88 (15)
C8—N2—C7—C6170.93 (9)N4—C15—C16—C17175.74 (9)
N1—C6—C7—O3178.12 (10)N5—C16—C17—C182.05 (16)
C5—C6—C7—O3−2.68 (15)C15—C16—C17—C18−175.83 (10)
N1—C6—C7—N2−1.24 (12)C16—C17—C18—C190.37 (16)
C5—C6—C7—N2177.96 (9)C17—C18—C19—C20−2.07 (16)
C7—N2—C8—O44.13 (18)C16—N5—C20—C190.70 (14)
C7—N2—C8—C9−173.76 (9)C16—N5—C20—C21179.34 (8)
C13—N3—C9—C10−0.73 (14)C18—C19—C20—N51.58 (15)
C13—N3—C9—C8177.19 (8)C18—C19—C20—C21−176.94 (9)
O4—C8—C9—N3167.30 (9)C24—O8—C21—O7−1.92 (13)
N2—C8—C9—N3−14.72 (12)C24—O8—C21—C20178.12 (8)
O4—C8—C9—C10−14.75 (15)N5—C20—C21—O7−19.00 (13)
N2—C8—C9—C10163.23 (9)C19—C20—C21—O7159.64 (10)
N3—C9—C10—C111.43 (15)N5—C20—C21—O8160.96 (8)
C8—C9—C10—C11−176.37 (10)C19—C20—C21—O8−20.40 (13)
C9—C10—C11—C12−0.44 (17)C1—O2—C22—C23170.48 (10)
C10—C11—C12—C13−1.12 (17)C21—O8—C24—C25168.94 (8)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
N4—H4···N30.885 (14)2.153 (14)2.6131 (13)111.7 (11)
N4—H4···N50.885 (14)2.158 (14)2.6297 (12)112.8 (11)
N2—H2···N30.878 (15)2.148 (14)2.6006 (12)111.4 (11)
N2—H2···N10.878 (15)2.151 (14)2.6329 (12)114.0 (11)

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB2864).

References

  • Huc, I. (2004). Eur. J. Org. Chem. pp. 17-29.
  • Li, X., Zhan, C., Wang, Y. & Yao, J. (2008). Chem. Commun. pp. 2444–2446. [PubMed]
  • Rigaku (1999). CrystalClear and CrystalStructure Rigaku Corporation, Tokyo, Japan.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]

Articles from Acta Crystallographica Section E: Structure Reports Online are provided here courtesy of International Union of Crystallography