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

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ISSN: 2056-9890

5,11-Di­methyl-6,12-dimeth­­oxy­indolo[3,2-b]carbazole

aUniversity Mainz, Duesbergweg 10-14, 55099 Mainz, Germany, and bLaboratoire de Chimie Moléculaire et Thio-organique, UMR 6507, ENSICAEN, 6 Boulevard Maréchal Juin, 14050 Caen, France
*Correspondence e-mail: detert@uni-mainz.de

(Received 14 January 2013; accepted 15 January 2013; online 19 January 2013)

The title compound, C22H20N2O2, was prepared in a twofold Cadogan cyclization followed by double N-methyl­ation. The crystal structure is characterized by a zigzag arrangement of centrosymmetric mol­ecules. The indolocarbazole framework is essentially planar [maximum deviation = 0.028 (2) Å] and the meth­oxy groups are orthogonal to this plane [C—C—O—C torsion angle = −88.2 (2)°]. The lengths of the C—N bonds are nearly identical and all C—C bonds of the pyrrole subunit are significantly longer than the C—C bonds in the benzene rings.

Related literature

For the synthesis of starting material see: Wrobel et al. (2012[Wrobel, N., Schollmeyer, D. & Detert, H. (2012). Acta Cryst. E68, o1022.]). For the Cadogan reaction, see: Cadogan (1962[Cadogan, J. I. G. (1962). Q. Rev. 16, 208-239.]); Peng et al. (2011[Peng, H., Chen, X., Chen, Y., He, Q., Xie, Y. & Yang, C. (2011). Tetrahedron, 67, 5725-5731.]). For other approaches to indolocarbazoles, see: Knölker & Reddy (2002[Knölker, H.-J. & Reddy, K. R. (2002). Chem. Rev. 39, 6521-6527.]); Katritzky et al. (1995[Katritzky, A. R., Li, J. & Stevens, C. V. (1995). J. Org. Chem. 60, 3401-3404.]). For the structure of N-unsubstituted indolocarbazole, see: Wrobel et al. (2013[Wrobel, N., Witulski, B., Schollmeyer, D. & Detert, H. (2013). Acta Cryst. E69, o116-o117.]). For electronic properties of indolocarbazoles, see: Hu et al. (1999[Hu, N.-X., Xie, S., Popovic, Z., Ong, B. & Hor, A.-M. (1999). J. Am. Chem. Soc. 121, 5097-5098.]); Wakim et al. (2004[Wakim, S., Bouchard, J., Simard, M., Drolet, N., Tao, Y. & Leclerc, M. (2004). Chem. Mater. 16, 4386-4388.]); Nemkovich et al. (2009[Nemkovich, N. A., Kruchenok, Yu. V., Sobchuk, A. N., Detert, H., Wrobel, N. & Chernyavskii, E. A. (2009). Opt. Spectrosc. 107, 275-281.]). For heteroanalogous carbazoles, see: Dassonneville et al. (2011[Dassonneville, B., Witulski, B. & Detert, H. (2011). Eur. J. Org. Chem. pp. 2836-2844.]); Letessier & Detert (2012[Letessier, J. & Detert, H. (2012). Synthesis, 44, 290-296.]); Nissen & Detert (2011[Nissen, F. & Detert, H. (2011). Eur. J. Org. Chem. pp. 2845-2854.]); Letessier et al. (2012[Letessier, J., Detert, H., Götz, K. & Opatz, T. (2012). Synthesis, 44, 747-754.]). For conjugated oligomers, see: Detert et al. (2010[Detert, H., Lehmann, M. & Meier, H. (2010). Materials, 3, 3218-3330.]).

[Scheme 1]

Experimental

Crystal data
  • C22H20N2O2

  • Mr = 344.40

  • Monoclinic, P 21 /c

  • a = 11.229 (4) Å

  • b = 7.8561 (7) Å

  • c = 9.668 (3) Å

  • β = 94.790 (17)°

  • V = 849.9 (4) Å3

  • Z = 2

  • Cu Kα radiation

  • μ = 0.69 mm−1

  • T = 193 K

  • 0.30 × 0.30 × 0.18 mm

Data collection
  • Enraf–Nonius CAD-4 diffractometer

  • 1716 measured reflections

  • 1612 independent reflections

  • 1410 reflections with I > 2σ(I)

  • Rint = 0.029

  • 3 standard reflections every 60 min intensity decay: 4%

Refinement
  • R[F2 > 2σ(F2)] = 0.049

  • wR(F2) = 0.152

  • S = 1.10

  • 1612 reflections

  • 120 parameters

  • H-atom parameters constrained

  • Δρmax = 0.25 e Å−3

  • Δρmin = −0.27 e Å−3

Data collection: CAD-4 Software (Enraf–Nonius, 1989[Enraf-Nonius (1989). CAD-4 Software. Enraf-Nonius, Delft, The Netherlands.]); cell refinement: CAD-4 Software; data reduction: CORINC (Dräger & Gattow, 1971[Dräger, M. & Gattow, G. (1971). Acta Chem. Scand. 25, 761-762.]); program(s) used to solve structure: SIR97 (Altomare et al., 1999[Altomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115-119.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]); software used to prepare material for publication: PLATON.

Supporting information


Comment top

As part of a larger project on the synthesis of carbazoles (Letessier & Detert, 2012) and carbolines (Dassonneville et al. 2011; Nissen & Detert, 2011; Letessier et al. 2012) indolo-annulated carbazoles were prepared for optoelectronic applications. The title compound is crystallographically centrosymmetric. The pentacyclic indolocarbazole framework is essentially planar with maximum deviations of 0.028 (2) Å from the mean plane. The dihedral angle between the mean plane of the aromatic system and the adjacent O-methyl unit (C8—C11—O12—C13) is -88.2 (2)°. The lengths of the C—N bond are nearly identical (N1—C2: = 1.378 (2) Å, N1—C9 = 1.392 (2) Å) and all CC bonds of the pyrrole subunit (C2—C7 = 1.412 (3) Å, C7—C8 = 1.442 (3) Å, 1.423 (2) Å) are significantly longer than the CC bonds in the benzene rings (C2—C3 = 1.396 (3) Å, 1.382 (3) Å, C4—C5 = 1.395 (3) Å, C5—C6 = 1.391 (3) Å, C6—C7 = 1.397 (3) Å, C8—C11 = 1.393 (3) Å, C9—C11 = 1.391 (2) Å).

Related literature top

For the synthesis of starting material see: Wrobel et al. (2012). For the Cadogan reaction, see: Cadogan (1962); Peng et al. (2011). For other approaches to indolocarbazoles, see: Knölker & Reddy (2002); Katritzky et al. (1995). For the structure of N-unsubstituted indolocarbazole, see: Wrobel et al. (2013). For electronic properties of indolocarbazoles, see: Hu et al. (1999); Wakim et al. (2004); Nemkovich et al. (2009). For heteroanalogous carbazoles, see: Dassonneville et al. (2011); Letessier & Detert (2012); Nissen & Detert (2011); Letessier et al. (2012). For conjugated oligomers, see: Detert et al. (2010).

Experimental top

5,11-Dimethyl-6,12-dimethoxyindolo[3,2-b]carbazole was prepared from 1,4-dimethoxy-2,5-bis(2-nitrophenyl)benzene (prepared analogous to Wrobel et al. 2012) via Cadogan cyclization. In a microwave reactor tube 300 mg of the dinitro-compound were mixed with triethyl phosphite (3 ml) and irradiated (300 W, 483 K) for 15 min. The cooled mixture was dissolved in ethyl acetate (50 ml), and the same amount of hydrochloric acid (6 N) was added and the mixture heated for 3 h to reflux. After dilution with water, the product was extracted with dichloromethane (3x), the pooled organic solutions were washed with brine, dried (MgSO4), and concentrated. Purification by column chromatography (SiO2, petroleum ether/ethyl acetate = 3/1 (v/v), Rf = 0.69). Yield: 664 mg (97%) of a brownish solid with m.p. = 530–531 K. Single crystals were grown by recrystallization from dichloromethane/propanol-2.

Refinement top

Hydrogen atoms attached to carbons were placed at calculated positions with C—H = 0.95 Å (aromatic) or 0.98–0.99 Å (sp3 C-atom). All H atoms were refined in the riding-model approximation with isotropic displacement parameters set at 1.2–1.5 times of the Ueq of the parent atom.

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software (Enraf–Nonius, 1989); data reduction: CORINC (Dräger & Gattow, 1971); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. Crystal structure of the title compound with labeling and displacement ellipsoids drawn at the 50% probability level. Symmetry code: i = 1 - x, 1 - y, 1 - z.
5,11-Dimethyl-6,12-dimethoxyindolo[3,2-b]carbazole top
Crystal data top
C22H20N2O2F(000) = 364
Mr = 344.40Dx = 1.346 Mg m3
Monoclinic, P21/cMelting point: 530 K
Hall symbol: -P 2ybcCu Kα radiation, λ = 1.54178 Å
a = 11.229 (4) ÅCell parameters from 25 reflections
b = 7.8561 (7) Åθ = 30–44°
c = 9.668 (3) ŵ = 0.69 mm1
β = 94.790 (17)°T = 193 K
V = 849.9 (4) Å3Plate, colourless
Z = 20.30 × 0.30 × 0.18 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer
Rint = 0.029
Radiation source: rotating anodeθmax = 70.0°, θmin = 4.0°
Graphite monochromatorh = 1313
ω/2θ scansk = 90
1716 measured reflectionsl = 110
1612 independent reflections3 standard reflections every 60 min
1410 reflections with I > 2σ(I) intensity decay: 4%
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)] = 0.049Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.152H-atom parameters constrained
S = 1.10 w = 1/[σ2(Fo2) + (0.0969P)2 + 0.1743P]
where P = (Fo2 + 2Fc2)/3
1612 reflections(Δ/σ)max < 0.001
120 parametersΔρmax = 0.25 e Å3
0 restraintsΔρmin = 0.27 e Å3
Crystal data top
C22H20N2O2V = 849.9 (4) Å3
Mr = 344.40Z = 2
Monoclinic, P21/cCu Kα radiation
a = 11.229 (4) ŵ = 0.69 mm1
b = 7.8561 (7) ÅT = 193 K
c = 9.668 (3) Å0.30 × 0.30 × 0.18 mm
β = 94.790 (17)°
Data collection top
Enraf–Nonius CAD-4
diffractometer
Rint = 0.029
1716 measured reflections3 standard reflections every 60 min
1612 independent reflections intensity decay: 4%
1410 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0490 restraints
wR(F2) = 0.152H-atom parameters constrained
S = 1.10Δρmax = 0.25 e Å3
1612 reflectionsΔρmin = 0.27 e Å3
120 parameters
Special details top

Experimental. H-NMR (400 MHz, CDCl3): 8.25 (d, J = 7.7 Hz, 2 H), 7.58 (d, J = 7.7 Hz, 2 H), 7.50 (dt, J = 7.7 Hz, J= 1.0 Hz, 2 H), 7.26 - 7.22 (m, 2 H), 4.17 (s, 6 H, CH3), 4.15 (s, CH3).

C-NMR (75 MHz, CDCl3): 145.2 (s), 136.4 (s), 128.5 (s), 125.6 (d), 122.7 (d), 121.5 (s), 118.7 (d), 117.8 (s), 108.0 (d), 61.8 (q), 31.2 (q).

IR (ATR) 3043, 2926, 2850, 2828, 1733, 1608, 1530, 1465, 1438, 1390, 1324, 1289, 1247, 1200, 1154, 1117, 1078, 1006, 933 cm-1.

MS (EI): 344 (100%) [M]+.

ESI-HRMS: C22H21N2O2 calcd.: 345.1603, found 345.1580.

UV-Vis (dichloromethane): λ = 393 nm, λmax = 412 nm; Fluorescence: λmax = 428 nm (dichloromethane).

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) top
xyzUiso*/Ueq
N10.25894 (13)0.42605 (18)0.48867 (15)0.0346 (4)
C20.21698 (16)0.4933 (2)0.36211 (18)0.0342 (4)
C30.10013 (17)0.4953 (2)0.3004 (2)0.0416 (5)
H30.03650.44470.34450.050*
C40.08055 (19)0.5736 (3)0.1724 (2)0.0476 (5)
H40.00180.57630.12820.057*
C50.1729 (2)0.6487 (2)0.1064 (2)0.0475 (5)
H50.15610.70230.01880.057*
C60.28932 (18)0.6459 (2)0.16765 (19)0.0397 (5)
H60.35240.69610.12230.048*
C70.31206 (16)0.56790 (19)0.29716 (18)0.0330 (4)
C80.41824 (15)0.54265 (19)0.38964 (17)0.0303 (4)
C90.38140 (15)0.45609 (19)0.50808 (17)0.0307 (4)
C100.18776 (17)0.3313 (3)0.5793 (2)0.0480 (5)
H10A0.11580.28860.52620.072*
H10B0.16480.40560.65400.072*
H10C0.23440.23510.61940.072*
C110.53766 (15)0.58538 (19)0.38040 (17)0.0306 (4)
O120.57194 (11)0.66686 (14)0.26343 (12)0.0364 (4)
C130.6004 (2)0.5500 (3)0.15737 (19)0.0480 (5)
H13A0.67340.48770.18820.072*
H13B0.61280.61300.07230.072*
H13C0.53440.46930.13910.072*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0362 (8)0.0301 (7)0.0376 (8)0.0027 (6)0.0035 (6)0.0014 (6)
C20.0405 (9)0.0242 (8)0.0376 (9)0.0030 (7)0.0014 (7)0.0048 (7)
C30.0375 (9)0.0346 (9)0.0524 (11)0.0047 (7)0.0018 (8)0.0054 (8)
C40.0440 (10)0.0399 (10)0.0564 (12)0.0108 (8)0.0101 (9)0.0038 (9)
C50.0569 (12)0.0346 (10)0.0486 (11)0.0073 (8)0.0107 (9)0.0039 (8)
C60.0507 (11)0.0269 (8)0.0404 (10)0.0003 (7)0.0032 (8)0.0018 (7)
C70.0414 (9)0.0209 (7)0.0362 (9)0.0002 (6)0.0008 (7)0.0032 (6)
C80.0414 (9)0.0197 (7)0.0297 (8)0.0015 (6)0.0018 (6)0.0019 (6)
C90.0381 (9)0.0211 (7)0.0332 (9)0.0027 (6)0.0044 (7)0.0023 (6)
C100.0382 (10)0.0556 (12)0.0509 (12)0.0064 (9)0.0085 (8)0.0114 (9)
C110.0425 (9)0.0202 (7)0.0295 (8)0.0030 (6)0.0049 (7)0.0001 (6)
O120.0488 (8)0.0283 (6)0.0327 (7)0.0052 (5)0.0060 (5)0.0053 (5)
C130.0740 (14)0.0391 (10)0.0323 (10)0.0070 (9)0.0123 (9)0.0010 (7)
Geometric parameters (Å, º) top
N1—C21.379 (2)C7—C81.443 (2)
N1—C91.392 (2)C8—C111.392 (2)
N1—C101.442 (2)C8—C91.423 (2)
C2—C31.396 (3)C9—C11i1.390 (2)
C2—C71.410 (3)C10—H10A0.9800
C3—C41.383 (3)C10—H10B0.9800
C3—H30.9500C10—H10C0.9800
C4—C51.393 (3)C11—O121.3818 (19)
C4—H40.9500C11—C9i1.390 (2)
C5—C61.390 (3)O12—C131.432 (2)
C5—H50.9500C13—H13A0.9800
C6—C71.398 (2)C13—H13B0.9800
C6—H60.9500C13—H13C0.9800
C2—N1—C9108.36 (14)C11—C8—C7132.65 (16)
C2—N1—C10124.86 (16)C9—C8—C7106.48 (15)
C9—N1—C10126.66 (15)C11i—C9—N1129.75 (16)
N1—C2—C3128.54 (17)C11i—C9—C8121.42 (16)
N1—C2—C7109.81 (16)N1—C9—C8108.83 (15)
C3—C2—C7121.65 (17)N1—C10—H10A109.5
C4—C3—C2117.46 (19)N1—C10—H10B109.5
C4—C3—H3121.3H10A—C10—H10B109.5
C2—C3—H3121.3N1—C10—H10C109.5
C3—C4—C5121.99 (19)H10A—C10—H10C109.5
C3—C4—H4119.0H10B—C10—H10C109.5
C5—C4—H4119.0O12—C11—C9i122.33 (15)
C6—C5—C4120.49 (19)O12—C11—C8119.98 (15)
C6—C5—H5119.8C9i—C11—C8117.69 (16)
C4—C5—H5119.8C11—O12—C13112.52 (13)
C5—C6—C7118.92 (19)O12—C13—H13A109.5
C5—C6—H6120.5O12—C13—H13B109.5
C7—C6—H6120.5H13A—C13—H13B109.5
C6—C7—C2119.49 (17)O12—C13—H13C109.5
C6—C7—C8134.00 (17)H13A—C13—H13C109.5
C2—C7—C8106.50 (15)H13B—C13—H13C109.5
C11—C8—C9120.87 (15)
C9—N1—C2—C3179.06 (16)C6—C7—C8—C9178.78 (17)
C10—N1—C2—C34.7 (3)C2—C7—C8—C91.05 (18)
C9—N1—C2—C70.16 (18)C2—N1—C9—C11i179.07 (16)
C10—N1—C2—C7176.07 (16)C10—N1—C9—C11i4.8 (3)
N1—C2—C3—C4179.03 (17)C2—N1—C9—C80.84 (18)
C7—C2—C3—C40.1 (3)C10—N1—C9—C8175.30 (16)
C2—C3—C4—C50.1 (3)C11—C8—C9—C11i1.4 (3)
C3—C4—C5—C60.5 (3)C7—C8—C9—C11i178.75 (14)
C4—C5—C6—C70.6 (3)C11—C8—C9—N1178.63 (14)
C5—C6—C7—C20.4 (2)C7—C8—C9—N11.17 (18)
C5—C6—C7—C8179.45 (18)C9—C8—C11—O12178.89 (13)
N1—C2—C7—C6179.29 (15)C7—C8—C11—O120.9 (3)
C3—C2—C7—C60.0 (2)C9—C8—C11—C9i1.4 (3)
N1—C2—C7—C80.57 (18)C7—C8—C11—C9i178.86 (16)
C3—C2—C7—C8179.85 (15)C9i—C11—O12—C1392.20 (19)
C6—C7—C8—C111.5 (3)C8—C11—O12—C1388.10 (19)
C2—C7—C8—C11178.72 (17)
Symmetry code: (i) x+1, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC22H20N2O2
Mr344.40
Crystal system, space groupMonoclinic, P21/c
Temperature (K)193
a, b, c (Å)11.229 (4), 7.8561 (7), 9.668 (3)
β (°) 94.790 (17)
V3)849.9 (4)
Z2
Radiation typeCu Kα
µ (mm1)0.69
Crystal size (mm)0.30 × 0.30 × 0.18
Data collection
DiffractometerEnraf–Nonius CAD-4
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
1716, 1612, 1410
Rint0.029
(sin θ/λ)max1)0.610
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.049, 0.152, 1.10
No. of reflections1612
No. of parameters120
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.25, 0.27

Computer programs: CAD-4 Software (Enraf–Nonius, 1989), CORINC (Dräger & Gattow, 1971), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009).

 

Acknowledgements

The authors are grateful to Heinz Kolshorn for helpful discussions.

References

First citationAltomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115–119.  Web of Science CrossRef CAS IUCr Journals
First citationCadogan, J. I. G. (1962). Q. Rev. 16, 208–239.  CrossRef CAS Web of Science
First citationDassonneville, B., Witulski, B. & Detert, H. (2011). Eur. J. Org. Chem. pp. 2836–2844.  Web of Science CSD CrossRef
First citationDetert, H., Lehmann, M. & Meier, H. (2010). Materials, 3, 3218–3330.  Web of Science CrossRef CAS
First citationDräger, M. & Gattow, G. (1971). Acta Chem. Scand. 25, 761–762.
First citationEnraf–Nonius (1989). CAD-4 Software. Enraf–Nonius, Delft, The Netherlands.
First citationHu, N.-X., Xie, S., Popovic, Z., Ong, B. & Hor, A.-M. (1999). J. Am. Chem. Soc. 121, 5097–5098.  Web of Science CSD CrossRef CAS
First citationKatritzky, A. R., Li, J. & Stevens, C. V. (1995). J. Org. Chem. 60, 3401–3404.  CrossRef CAS Web of Science
First citationKnölker, H.-J. & Reddy, K. R. (2002). Chem. Rev. 39, 6521–6527.
First citationLetessier, J. & Detert, H. (2012). Synthesis, 44, 290–296.  CAS
First citationLetessier, J., Detert, H., Götz, K. & Opatz, T. (2012). Synthesis, 44, 747–754.  CAS
First citationNemkovich, N. A., Kruchenok, Yu. V., Sobchuk, A. N., Detert, H., Wrobel, N. & Chernyavskii, E. A. (2009). Opt. Spectrosc. 107, 275–281.  Web of Science CrossRef CAS
First citationNissen, F. & Detert, H. (2011). Eur. J. Org. Chem. pp. 2845–2854.  Web of Science CSD CrossRef
First citationPeng, H., Chen, X., Chen, Y., He, Q., Xie, Y. & Yang, C. (2011). Tetrahedron, 67, 5725–5731.  Web of Science CrossRef CAS
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals
First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals
First citationWakim, S., Bouchard, J., Simard, M., Drolet, N., Tao, Y. & Leclerc, M. (2004). Chem. Mater. 16, 4386–4388.  Web of Science CSD CrossRef CAS
First citationWrobel, N., Schollmeyer, D. & Detert, H. (2012). Acta Cryst. E68, o1022.  CSD CrossRef IUCr Journals
First citationWrobel, N., Witulski, B., Schollmeyer, D. & Detert, H. (2013). Acta Cryst. E69, o116–o117.  CSD CrossRef IUCr Journals

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