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ISSN: 2056-9890

9-Ethyl-3,6-bis­­(1H-imidazol-1-yl)-9H-carbazole

aDepartment of Chemistry, Anhui University, Hefei 230039, Peoples Republic of China and, Key Laboratory of Opto-Electronic Information Acquisition and, Manipulation (Anhui University), Ministry of Education, Hefei 230039, People's Republic of China
*Correspondence e-mail: zhpzhp@263.net

(Received 28 March 2008; accepted 9 May 2008; online 14 May 2008)

In the crystal structure of the title compound, C20H17N5, the two imidazole rings are twisted with respect to the carbazole plane, making dihedral angles of 55.8 (2) and 43.7 (2)°. The crystal structure is stabilized by weak C—H⋯N and C—H⋯π inter­actions.

Related literature

For general background, see: Mi et al. (2003[Mi, B. X., Wang, P. F., Liu, M. W., Kwong, H. L., Wong, N. B., Lee, C. S. & Lee, S. T. (2003). Chem. Mater. 15, 3148-3151.]).

[Scheme 1]

Experimental

Crystal data
  • C20H17N5

  • Mr = 327.39

  • Triclinic, [P \overline 1]

  • a = 5.625 (2) Å

  • b = 8.826 (3) Å

  • c = 17.367 (6) Å

  • α = 92.698 (6)°

  • β = 96.011 (6)°

  • γ = 102.567 (6)°

  • V = 834.8 (5) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.08 mm−1

  • T = 293 (2) K

  • 0.46 × 0.40 × 0.16 mm

Data collection
  • Bruker SMART APEX area-dectector diffractometer

  • Absorption correction: none

  • 6040 measured reflections

  • 2928 independent reflections

  • 2611 reflections with I > 2σ(I)

  • Rint = 0.017

Refinement
  • R[F2 > 2σ(F2)] = 0.039

  • wR(F2) = 0.120

  • S = 1.06

  • 2928 reflections

  • 225 parameters

  • H-atom parameters constrained

  • Δρmax = 0.23 e Å−3

  • Δρmin = −0.18 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C1—H1⋯N1i 0.93 2.73 3.533 (2) 144
C2—H2⋯N1ii 0.93 2.63 3.452 (2) 148
C16—H16⋯N5ii 0.93 2.68 3.509 (2) 149
C14—H14⋯N5iii 0.93 2.66 3.570 (2) 165
Symmetry codes: (i) -x, -y, -z; (ii) x+1, y, z; (iii) -x+1, -y+1, -z+1.

Data collection: SMART (Bruker, 2002[Bruker (2002). SMART and SAINT, Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2002[Bruker (2002). 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: ORTEPII (Johnson, 1976[Johnson, C. K. (1976). ORTEPII. Report ORNL-5138. Oak Ridge National Laboratory, Tennessee, USA.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

Carbazole derivatives exhibit good charge transfer and hole transporting properties, which are being explored for a multitude of optoelectronic and photocatalytic applications, including organic light emitting diodes (OLEDs) (Mi et al., 2003). The title molecule containing imidazole with electrochemical and biology properties has been prepared, its crystal structure is reported here.

The molecular structure is shown in Fig. 1, the bond lengths and angles are normal. The dihedral angles between N2-imidazole and C4-benzene rings and between N4-imidazole and C10-benzene rings are 55.8 (2) and 43.7 (2)°, respectively. In the crystal structure, the molecules are stacked through the weak C19—H19A···Cgi interactions (Cg is the centroid of the N1-imidazole ring), H19A···Cgi = 2.85 Å, C19···Cgi = 3.640 (11) Å and C19—H19A···Cgi = 139° [symmetry code: (i) -1 + x, -1 + y, z]. The weak C—H···N hydrogen bonding (Table 1) helps to stabilize the crystal structure.

Related literature top

For general background, see: Mi et al. (2003).

Experimental top

For the preparation of 3,6-diimidazolyl-9-ethylcarbazole, a mixture of CuI (0.27 g, 1.40 mmol) and 1,10-phenanthroline (0.60 g, 3.00 mmol) were heated at 393 K with DMF (3 ml) as solvent for 10 min. Then, the mixture was cooled to room temperature, potassium tert-butanol (6.05 g, 54.00 mmol), imidazole (3.65 g, 54.00 mmol), 3,6-diiodo-9-ethylcarbazole (3.00 g, 6.70 mmol) and 18-crown-6 (litter) were added and heated at 413 k for 48 h, then the reaction mixture was heated to 433 k for 12 h, and cooled to room temperature. The mixture solution was poured into water and extracted by dichloromethane. The organic layer was separated, dried with anhydrous magnesium sulfate. Then it was filtered and concentrated, the re-crystallization from ethyl acetate produced light yellow single crystals (1.50 g, Yield 70.0%).

Refinement top

All hydrogen atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H = 0.93 - 0.96 Å and Uiso(H) = 1.2Ueq(C) or 1.5Ueq(C).

Computing details top

Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound showing 50% probability displacement ellipsoids.
9-Ethyl-3,6-bis(1H-imidazol-1-yl)-9H-carbazole top
Crystal data top
C20H17N5Z = 2
Mr = 327.39F(000) = 344
Triclinic, P1Dx = 1.302 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 5.625 (2) ÅCell parameters from 2928 reflections
b = 8.826 (3) Åθ = 1.2–25.0°
c = 17.367 (6) ŵ = 0.08 mm1
α = 92.698 (6)°T = 293 K
β = 96.011 (6)°Prism, yellow
γ = 102.567 (6)°0.46 × 0.40 × 0.16 mm
V = 834.8 (5) Å3
Data collection top
Bruker SMART APEX area-dectector
diffractometer
2611 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.017
Graphite monochromatorθmax = 25.0°, θmin = 1.2°
ϕ and ω scansh = 66
6040 measured reflectionsk = 1010
2928 independent reflectionsl = 2020
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.039H-atom parameters constrained
wR(F2) = 0.120 w = 1/[σ2(Fo2) + (0.0695P)2 + 0.1471P]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max < 0.001
2928 reflectionsΔρmax = 0.23 e Å3
225 parametersΔρmin = 0.18 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.044 (6)
Crystal data top
C20H17N5γ = 102.567 (6)°
Mr = 327.39V = 834.8 (5) Å3
Triclinic, P1Z = 2
a = 5.625 (2) ÅMo Kα radiation
b = 8.826 (3) ŵ = 0.08 mm1
c = 17.367 (6) ÅT = 293 K
α = 92.698 (6)°0.46 × 0.40 × 0.16 mm
β = 96.011 (6)°
Data collection top
Bruker SMART APEX area-dectector
diffractometer
2611 reflections with I > 2σ(I)
6040 measured reflectionsRint = 0.017
2928 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0390 restraints
wR(F2) = 0.120H-atom parameters constrained
S = 1.06Δρmax = 0.23 e Å3
2928 reflectionsΔρmin = 0.18 e Å3
225 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N20.49085 (19)0.34017 (13)0.10310 (6)0.0435 (3)
N40.89546 (19)0.72250 (13)0.53896 (6)0.0418 (3)
N50.6235 (2)0.67394 (15)0.62354 (7)0.0553 (4)
N10.1184 (2)0.19639 (15)0.06703 (7)0.0535 (3)
N31.2016 (2)0.83688 (14)0.24918 (7)0.0484 (3)
C130.9898 (2)0.75062 (15)0.46637 (7)0.0405 (3)
C50.8279 (3)0.56084 (17)0.09187 (8)0.0485 (4)
H50.80100.53960.03830.058*
C90.7148 (2)0.49327 (16)0.21905 (7)0.0432 (3)
H90.61790.42890.25000.052*
C121.1789 (2)0.88178 (16)0.46167 (8)0.0459 (4)
H121.24630.94560.50620.055*
C71.0438 (2)0.71535 (16)0.20364 (8)0.0438 (3)
C101.1590 (2)0.82136 (16)0.32594 (8)0.0433 (3)
C111.2661 (2)0.91729 (16)0.39191 (8)0.0476 (4)
H111.39331.00320.38900.057*
C80.8970 (2)0.62019 (15)0.25193 (7)0.0416 (3)
C140.8859 (2)0.65280 (15)0.40123 (7)0.0430 (3)
H140.76240.56520.40480.052*
C20.5129 (3)0.22459 (17)0.05004 (8)0.0493 (4)
H20.65690.20930.03230.059*
C180.6561 (2)0.68650 (16)0.55011 (8)0.0480 (4)
H180.52810.67220.51010.058*
C150.9703 (2)0.68841 (15)0.33029 (7)0.0416 (3)
C10.2852 (3)0.13828 (17)0.02886 (8)0.0515 (4)
H10.24600.05170.00650.062*
C61.0107 (3)0.68540 (17)0.12343 (8)0.0496 (4)
H61.10900.74760.09200.060*
C40.6822 (2)0.46580 (16)0.13922 (7)0.0423 (3)
C161.0248 (3)0.73427 (18)0.61152 (8)0.0503 (4)
H161.19440.75840.62350.060*
C191.3664 (3)0.96821 (17)0.22027 (9)0.0535 (4)
H19A1.38621.05910.25600.064*
H19B1.29210.99140.17050.064*
C30.2492 (2)0.31619 (17)0.11053 (8)0.0473 (4)
H30.18320.37840.14320.057*
C170.8562 (3)0.70373 (19)0.66187 (8)0.0553 (4)
H170.89290.70300.71530.066*
C201.6114 (4)0.9380 (3)0.21097 (14)0.0896 (6)
H20A1.68720.91670.26020.134*
H20B1.71201.02790.19230.134*
H20C1.59360.85010.17440.134*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N20.0408 (6)0.0507 (7)0.0374 (6)0.0095 (5)0.0013 (4)0.0020 (5)
N40.0403 (6)0.0420 (6)0.0403 (6)0.0042 (5)0.0040 (5)0.0012 (5)
N50.0514 (7)0.0583 (8)0.0555 (8)0.0067 (6)0.0152 (6)0.0044 (6)
N10.0427 (6)0.0611 (8)0.0533 (7)0.0076 (6)0.0006 (5)0.0001 (6)
N30.0488 (7)0.0466 (7)0.0447 (7)0.0022 (5)0.0084 (5)0.0065 (5)
C130.0394 (7)0.0409 (7)0.0390 (7)0.0047 (5)0.0032 (5)0.0012 (5)
C50.0521 (8)0.0574 (9)0.0353 (7)0.0114 (7)0.0047 (6)0.0030 (6)
C90.0449 (7)0.0436 (7)0.0383 (7)0.0042 (6)0.0046 (5)0.0022 (5)
C120.0446 (7)0.0426 (8)0.0448 (8)0.0011 (6)0.0003 (6)0.0031 (6)
C70.0438 (7)0.0449 (8)0.0416 (7)0.0066 (6)0.0056 (5)0.0053 (6)
C100.0418 (7)0.0415 (7)0.0441 (7)0.0032 (6)0.0052 (5)0.0050 (6)
C110.0429 (7)0.0419 (8)0.0508 (8)0.0048 (6)0.0032 (6)0.0029 (6)
C80.0433 (7)0.0413 (7)0.0380 (7)0.0044 (6)0.0051 (5)0.0040 (5)
C140.0431 (7)0.0388 (7)0.0423 (7)0.0003 (6)0.0040 (6)0.0016 (6)
C20.0449 (8)0.0552 (9)0.0468 (8)0.0118 (6)0.0047 (6)0.0083 (6)
C180.0394 (7)0.0499 (8)0.0505 (8)0.0019 (6)0.0051 (6)0.0001 (6)
C150.0424 (7)0.0381 (7)0.0407 (7)0.0015 (6)0.0034 (5)0.0035 (5)
C10.0513 (8)0.0511 (8)0.0483 (8)0.0082 (7)0.0004 (6)0.0066 (6)
C60.0501 (8)0.0552 (9)0.0423 (8)0.0051 (7)0.0107 (6)0.0101 (6)
C40.0397 (7)0.0461 (8)0.0400 (7)0.0090 (6)0.0017 (5)0.0001 (6)
C160.0441 (7)0.0650 (9)0.0411 (8)0.0121 (6)0.0021 (6)0.0021 (6)
C190.0554 (9)0.0474 (8)0.0565 (9)0.0047 (7)0.0124 (7)0.0122 (7)
C30.0406 (7)0.0574 (9)0.0442 (7)0.0124 (6)0.0045 (6)0.0001 (6)
C170.0595 (9)0.0679 (10)0.0404 (8)0.0165 (7)0.0082 (6)0.0074 (7)
C200.0618 (11)0.0954 (15)0.1158 (18)0.0141 (10)0.0283 (11)0.0259 (13)
Geometric parameters (Å, º) top
N2—C31.3501 (17)C7—C61.391 (2)
N2—C21.3769 (18)C7—C81.4142 (18)
N2—C41.4336 (18)C10—C111.3909 (19)
N4—C181.3512 (18)C10—C151.4116 (19)
N4—C161.3750 (18)C11—H110.9300
N4—C131.4299 (17)C8—C151.4428 (19)
N5—C181.3135 (19)C14—C151.3913 (19)
N5—C171.370 (2)C14—H140.9300
N1—C31.3039 (18)C2—C11.344 (2)
N1—C11.3748 (19)C2—H20.9300
N3—C71.3867 (18)C18—H180.9300
N3—C101.3867 (18)C1—H10.9300
N3—C191.4629 (18)C6—H60.9300
C13—C141.3844 (18)C16—C171.350 (2)
C13—C121.403 (2)C16—H160.9300
C5—C61.378 (2)C19—C201.483 (2)
C5—C41.400 (2)C19—H19A0.9700
C5—H50.9300C19—H19B0.9700
C9—C41.3820 (19)C3—H30.9300
C9—C81.3960 (18)C17—H170.9300
C9—H90.9300C20—H20A0.9600
C12—C111.378 (2)C20—H20B0.9600
C12—H120.9300C20—H20C0.9600
C3—N2—C2105.71 (11)C1—C2—H2126.8
C3—N2—C4127.00 (11)N2—C2—H2126.8
C2—N2—C4127.18 (11)N5—C18—N4112.78 (12)
C18—N4—C16105.83 (11)N5—C18—H18123.6
C18—N4—C13126.09 (11)N4—C18—H18123.6
C16—N4—C13128.00 (11)C14—C15—C10119.99 (12)
C18—N5—C17104.42 (12)C14—C15—C8133.50 (12)
C3—N1—C1104.81 (11)C10—C15—C8106.43 (12)
C7—N3—C10108.52 (11)C2—C1—N1110.27 (13)
C7—N3—C19125.61 (12)C2—C1—H1124.9
C10—N3—C19125.58 (12)N1—C1—H1124.9
C14—C13—C12121.06 (12)C5—C6—C7118.08 (13)
C14—C13—N4119.69 (12)C5—C6—H6121.0
C12—C13—N4119.18 (11)C7—C6—H6121.0
C6—C5—C4120.98 (13)C9—C4—C5121.53 (13)
C6—C5—H5119.5C9—C4—N2119.89 (12)
C4—C5—H5119.5C5—C4—N2118.56 (12)
C4—C9—C8118.25 (13)C17—C16—N4106.22 (13)
C4—C9—H9120.9C17—C16—H16126.9
C8—C9—H9120.9N4—C16—H16126.9
C11—C12—C13120.91 (12)N3—C19—C20112.98 (14)
C11—C12—H12119.5N3—C19—H19A109.0
C13—C12—H12119.5C20—C19—H19A109.0
N3—C7—C6129.66 (13)N3—C19—H19B109.0
N3—C7—C8108.93 (12)C20—C19—H19B109.0
C6—C7—C8121.33 (13)H19A—C19—H19B107.8
N3—C10—C11129.53 (13)N1—C3—N2112.77 (12)
N3—C10—C15109.31 (12)N1—C3—H3123.6
C11—C10—C15121.11 (13)N2—C3—H3123.6
C12—C11—C10118.32 (13)C16—C17—N5110.75 (13)
C12—C11—H11120.8C16—C17—H17124.6
C10—C11—H11120.8N5—C17—H17124.6
C9—C8—C7119.82 (12)C19—C20—H20A109.5
C9—C8—C15133.27 (12)C19—C20—H20B109.5
C7—C8—C15106.82 (12)H20A—C20—H20B109.5
C13—C14—C15118.58 (12)C19—C20—H20C109.5
C13—C14—H14120.7H20A—C20—H20C109.5
C15—C14—H14120.7H20B—C20—H20C109.5
C1—C2—N2106.44 (12)
C18—N4—C13—C1444.43 (19)C13—C14—C15—C8175.75 (14)
C16—N4—C13—C14139.43 (14)N3—C10—C15—C14176.74 (11)
C18—N4—C13—C12132.48 (14)C11—C10—C15—C141.0 (2)
C16—N4—C13—C1243.66 (19)N3—C10—C15—C80.35 (15)
C14—C13—C12—C110.2 (2)C11—C10—C15—C8178.06 (12)
N4—C13—C12—C11176.63 (11)C9—C8—C15—C140.2 (3)
C10—N3—C7—C6176.82 (13)C7—C8—C15—C14176.22 (14)
C19—N3—C7—C62.8 (2)C9—C8—C15—C10176.67 (14)
C10—N3—C7—C80.07 (15)C7—C8—C15—C100.30 (15)
C19—N3—C7—C8173.96 (13)N2—C2—C1—N10.16 (17)
C7—N3—C10—C11177.73 (13)C3—N1—C1—C20.17 (17)
C19—N3—C10—C113.7 (2)C4—C5—C6—C70.9 (2)
C7—N3—C10—C150.26 (16)N3—C7—C6—C5175.61 (13)
C19—N3—C10—C15173.77 (13)C8—C7—C6—C50.8 (2)
C13—C12—C11—C101.1 (2)C8—C9—C4—C50.6 (2)
N3—C10—C11—C12175.49 (13)C8—C9—C4—N2177.63 (11)
C15—C10—C11—C121.7 (2)C6—C5—C4—C90.3 (2)
C4—C9—C8—C70.7 (2)C6—C5—C4—N2178.49 (12)
C4—C9—C8—C15175.30 (14)C3—N2—C4—C955.86 (19)
N3—C7—C8—C9177.10 (12)C2—N2—C4—C9128.49 (15)
C6—C7—C8—C90.0 (2)C3—N2—C4—C5122.38 (15)
N3—C7—C8—C150.15 (15)C2—N2—C4—C553.27 (19)
C6—C7—C8—C15176.93 (13)C18—N4—C16—C170.40 (16)
C12—C13—C14—C151.0 (2)C13—N4—C16—C17177.15 (13)
N4—C13—C14—C15175.86 (11)C7—N3—C19—C2089.67 (19)
C3—N2—C2—C10.09 (16)C10—N3—C19—C2097.30 (19)
C4—N2—C2—C1176.48 (13)C1—N1—C3—N20.11 (16)
C17—N5—C18—N40.02 (16)C2—N2—C3—N10.02 (16)
C16—N4—C18—N50.26 (16)C4—N2—C3—N1176.39 (12)
C13—N4—C18—N5177.10 (12)N4—C16—C17—N50.41 (18)
C13—C14—C15—C100.4 (2)C18—N5—C17—C160.24 (17)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1···N1i0.932.733.533 (2)144
C2—H2···N1ii0.932.633.452 (2)148
C16—H16···N5ii0.932.683.509 (2)149
C14—H14···N5iii0.932.663.570 (2)165
Symmetry codes: (i) x, y, z; (ii) x+1, y, z; (iii) x+1, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC20H17N5
Mr327.39
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)5.625 (2), 8.826 (3), 17.367 (6)
α, β, γ (°)92.698 (6), 96.011 (6), 102.567 (6)
V3)834.8 (5)
Z2
Radiation typeMo Kα
µ (mm1)0.08
Crystal size (mm)0.46 × 0.40 × 0.16
Data collection
DiffractometerBruker SMART APEX area-dectector
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
6040, 2928, 2611
Rint0.017
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.039, 0.120, 1.06
No. of reflections2928
No. of parameters225
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.23, 0.18

Computer programs: SMART (Bruker, 2002), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEPII (Johnson, 1976).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1···N1i0.932.733.533 (2)144.4
C2—H2···N1ii0.932.633.452 (2)147.5
C16—H16···N5ii0.932.683.509 (2)149.4
C14—H14···N5iii0.932.663.570 (2)165.0
Symmetry codes: (i) x, y, z; (ii) x+1, y, z; (iii) x+1, y+1, z+1.
 

Acknowledgements

This work was supported by the National Natural Science Foundation of China (50532030, 50703001 and 20771001), the Natural Science Foundation of Anhui Province, China (070414188), the Doctoral Program Foundation of the Ministry of Education of China, the Education Committee of Anhui Province, China (2006K J032A), the Team for Scientific Innovation Foundation of Anhui Province (2006K J007TD), the Young Teacher Foundation of Institutions of Higher Education of Anhui Province (2007jq1019), the Ministry of Education and the Persons with Ability Foundation of Anhui University, China.

References

First citationBruker (2002). SMART and SAINT, Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationJohnson, C. K. (1976). ORTEPII. Report ORNL-5138. Oak Ridge National Laboratory, Tennessee, USA.  Google Scholar
First citationMi, B. X., Wang, P. F., Liu, M. W., Kwong, H. L., Wong, N. B., Lee, C. S. & Lee, S. T. (2003). Chem. Mater. 15, 3148–3151.  Web of Science CrossRef CAS Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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