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

Wrobel, N.; Witulski, B.; Schollmeyer, D.; Detert, H.

doi:10.1107/S1600536813001463

organic compounds

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ISSN: 2056-9890

Volume 69| Part 2| February 2013| Page o255

doi:10.1107/S1600536813001463

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

Norma Wrobel,^a Bernhard Witulski,^b Dieter Schollmeyer ^a and Heiner Detert ^a ^*

^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 ). 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

Crystal data

C₂₂H₂₀N₂O₂
M_r = 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)
R_int = 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
Δρ_max = 0.25 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Data collection: CAD-4 Software (Enraf–Nonius, 1989 ); cell refinement: CAD-4 Software; 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.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536813001463/bt6882sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536813001463/bt6882Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536813001463/bt6882Isup3.cml

checkCIF report

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), R_f = 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.

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

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

C₂₂H₂₀N₂O₂	F(000) = 364
M_r = 344.40	D_x = 1.346 Mg m⁻³
Monoclinic, P2₁/c	Melting point: 530 K
Hall symbol: -P 2ybc	Cu Kα radiation, λ = 1.54178 Å
a = 11.229 (4) Å	Cell parameters from 25 reflections
b = 7.8561 (7) Å	θ = 30–44°
c = 9.668 (3) Å	µ = 0.69 mm⁻¹
β = 94.790 (17)°	T = 193 K
V = 849.9 (4) Å³	Plate, colourless
Z = 2	0.30 × 0.30 × 0.18 mm

Data collection top

Enraf–Nonius CAD-4 diffractometer	R_int = 0.029
Radiation source: rotating anode	θ_max = 70.0°, θ_min = 4.0°
Graphite monochromator	h = −13→13
ω/2θ scans	k = −9→0
1716 measured reflections	l = −11→0
1612 independent reflections	3 standard reflections every 60 min
1410 reflections with I > 2σ(I)	intensity decay: 4%

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.152	H-atom parameters constrained
S = 1.10	w = 1/[σ²(F_o²) + (0.0969P)² + 0.1743P] where P = (F_o² + 2F_c²)/3
1612 reflections	(Δ/σ)_max < 0.001
120 parameters	Δρ_max = 0.25 e Å⁻³
0 restraints	Δρ_min = −0.27 e Å⁻³

Crystal data top

C₂₂H₂₀N₂O₂	V = 849.9 (4) Å³
M_r = 344.40	Z = 2
Monoclinic, P2₁/c	Cu Kα radiation
a = 11.229 (4) Å	µ = 0.69 mm⁻¹
b = 7.8561 (7) Å	T = 193 K
c = 9.668 (3) Å	0.30 × 0.30 × 0.18 mm
β = 94.790 (17)°

Data collection top

Enraf–Nonius CAD-4 diffractometer	R_int = 0.029
1716 measured reflections	3 standard reflections every 60 min
1612 independent reflections	intensity decay: 4%
1410 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.049	0 restraints
wR(F²) = 0.152	H-atom parameters constrained
S = 1.10	Δρ_max = 0.25 e Å⁻³
1612 reflections	Δρ_min = −0.27 e Å⁻³
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, λ_max = 412 nm; Fluorescence: λ_max = 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

	x	y	z	U_iso*/U_eq
N1	0.25894 (13)	0.42605 (18)	0.48867 (15)	0.0346 (4)
C2	0.21698 (16)	0.4933 (2)	0.36211 (18)	0.0342 (4)
C3	0.10013 (17)	0.4953 (2)	0.3004 (2)	0.0416 (5)
H3	0.0365	0.4447	0.3445	0.050*
C4	0.08055 (19)	0.5736 (3)	0.1724 (2)	0.0476 (5)
H4	0.0018	0.5763	0.1282	0.057*
C5	0.1729 (2)	0.6487 (2)	0.1064 (2)	0.0475 (5)
H5	0.1561	0.7023	0.0188	0.057*
C6	0.28932 (18)	0.6459 (2)	0.16765 (19)	0.0397 (5)
H6	0.3524	0.6961	0.1223	0.048*
C7	0.31206 (16)	0.56790 (19)	0.29716 (18)	0.0330 (4)
C8	0.41824 (15)	0.54265 (19)	0.38964 (17)	0.0303 (4)
C9	0.38140 (15)	0.45609 (19)	0.50808 (17)	0.0307 (4)
C10	0.18776 (17)	0.3313 (3)	0.5793 (2)	0.0480 (5)
H10A	0.1158	0.2886	0.5262	0.072*
H10B	0.1648	0.4056	0.6540	0.072*
H10C	0.2344	0.2351	0.6194	0.072*
C11	0.53766 (15)	0.58538 (19)	0.38040 (17)	0.0306 (4)
O12	0.57194 (11)	0.66686 (14)	0.26343 (12)	0.0364 (4)
C13	0.6004 (2)	0.5500 (3)	0.15737 (19)	0.0480 (5)
H13A	0.6734	0.4877	0.1882	0.072*
H13B	0.6128	0.6130	0.0723	0.072*
H13C	0.5344	0.4693	0.1391	0.072*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0362 (8)	0.0301 (7)	0.0376 (8)	−0.0027 (6)	0.0035 (6)	0.0014 (6)
C2	0.0405 (9)	0.0242 (8)	0.0376 (9)	0.0030 (7)	0.0014 (7)	−0.0048 (7)
C3	0.0375 (9)	0.0346 (9)	0.0524 (11)	0.0047 (7)	0.0018 (8)	−0.0054 (8)
C4	0.0440 (10)	0.0399 (10)	0.0564 (12)	0.0108 (8)	−0.0101 (9)	−0.0038 (9)
C5	0.0569 (12)	0.0346 (10)	0.0486 (11)	0.0073 (8)	−0.0107 (9)	0.0039 (8)
C6	0.0507 (11)	0.0269 (8)	0.0404 (10)	0.0003 (7)	−0.0032 (8)	0.0018 (7)
C7	0.0414 (9)	0.0209 (7)	0.0362 (9)	−0.0002 (6)	0.0008 (7)	−0.0032 (6)
C8	0.0414 (9)	0.0197 (7)	0.0297 (8)	−0.0015 (6)	0.0018 (6)	−0.0019 (6)
C9	0.0381 (9)	0.0211 (7)	0.0332 (9)	−0.0027 (6)	0.0044 (7)	−0.0023 (6)
C10	0.0382 (10)	0.0556 (12)	0.0509 (12)	−0.0064 (9)	0.0085 (8)	0.0114 (9)
C11	0.0425 (9)	0.0202 (7)	0.0295 (8)	−0.0030 (6)	0.0049 (7)	0.0001 (6)
O12	0.0488 (8)	0.0283 (6)	0.0327 (7)	−0.0052 (5)	0.0060 (5)	0.0053 (5)
C13	0.0740 (14)	0.0391 (10)	0.0323 (10)	−0.0070 (9)	0.0123 (9)	0.0010 (7)

Geometric parameters (Å, º) top

N1—C2	1.379 (2)	C7—C8	1.443 (2)
N1—C9	1.392 (2)	C8—C11	1.392 (2)
N1—C10	1.442 (2)	C8—C9	1.423 (2)
C2—C3	1.396 (3)	C9—C11ⁱ	1.390 (2)
C2—C7	1.410 (3)	C10—H10A	0.9800
C3—C4	1.383 (3)	C10—H10B	0.9800
C3—H3	0.9500	C10—H10C	0.9800
C4—C5	1.393 (3)	C11—O12	1.3818 (19)
C4—H4	0.9500	C11—C9ⁱ	1.390 (2)
C5—C6	1.390 (3)	O12—C13	1.432 (2)
C5—H5	0.9500	C13—H13A	0.9800
C6—C7	1.398 (2)	C13—H13B	0.9800
C6—H6	0.9500	C13—H13C	0.9800

C2—N1—C9	108.36 (14)	C11—C8—C7	132.65 (16)
C2—N1—C10	124.86 (16)	C9—C8—C7	106.48 (15)
C9—N1—C10	126.66 (15)	C11ⁱ—C9—N1	129.75 (16)
N1—C2—C3	128.54 (17)	C11ⁱ—C9—C8	121.42 (16)
N1—C2—C7	109.81 (16)	N1—C9—C8	108.83 (15)
C3—C2—C7	121.65 (17)	N1—C10—H10A	109.5
C4—C3—C2	117.46 (19)	N1—C10—H10B	109.5
C4—C3—H3	121.3	H10A—C10—H10B	109.5
C2—C3—H3	121.3	N1—C10—H10C	109.5
C3—C4—C5	121.99 (19)	H10A—C10—H10C	109.5
C3—C4—H4	119.0	H10B—C10—H10C	109.5
C5—C4—H4	119.0	O12—C11—C9ⁱ	122.33 (15)
C6—C5—C4	120.49 (19)	O12—C11—C8	119.98 (15)
C6—C5—H5	119.8	C9ⁱ—C11—C8	117.69 (16)
C4—C5—H5	119.8	C11—O12—C13	112.52 (13)
C5—C6—C7	118.92 (19)	O12—C13—H13A	109.5
C5—C6—H6	120.5	O12—C13—H13B	109.5
C7—C6—H6	120.5	H13A—C13—H13B	109.5
C6—C7—C2	119.49 (17)	O12—C13—H13C	109.5
C6—C7—C8	134.00 (17)	H13A—C13—H13C	109.5
C2—C7—C8	106.50 (15)	H13B—C13—H13C	109.5
C11—C8—C9	120.87 (15)

C9—N1—C2—C3	−179.06 (16)	C6—C7—C8—C9	178.78 (17)
C10—N1—C2—C3	4.7 (3)	C2—C7—C8—C9	−1.05 (18)
C9—N1—C2—C7	0.16 (18)	C2—N1—C9—C11ⁱ	179.07 (16)
C10—N1—C2—C7	−176.07 (16)	C10—N1—C9—C11ⁱ	−4.8 (3)
N1—C2—C3—C4	179.03 (17)	C2—N1—C9—C8	−0.84 (18)
C7—C2—C3—C4	−0.1 (3)	C10—N1—C9—C8	175.30 (16)
C2—C3—C4—C5	−0.1 (3)	C11—C8—C9—C11ⁱ	1.4 (3)
C3—C4—C5—C6	0.5 (3)	C7—C8—C9—C11ⁱ	−178.75 (14)
C4—C5—C6—C7	−0.6 (3)	C11—C8—C9—N1	−178.63 (14)
C5—C6—C7—C2	0.4 (2)	C7—C8—C9—N1	1.17 (18)
C5—C6—C7—C8	−179.45 (18)	C9—C8—C11—O12	178.89 (13)
N1—C2—C7—C6	−179.29 (15)	C7—C8—C11—O12	−0.9 (3)
C3—C2—C7—C6	−0.0 (2)	C9—C8—C11—C9ⁱ	−1.4 (3)
N1—C2—C7—C8	0.57 (18)	C7—C8—C11—C9ⁱ	178.86 (16)
C3—C2—C7—C8	179.85 (15)	C9ⁱ—C11—O12—C13	92.20 (19)
C6—C7—C8—C11	−1.5 (3)	C8—C11—O12—C13	−88.10 (19)
C2—C7—C8—C11	178.72 (17)

Symmetry code: (i) −x+1, −y+1, −z+1.

Experimental details

Crystal data
Chemical formula	C₂₂H₂₀N₂O₂
M_r	344.40
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	193
a, b, c (Å)	11.229 (4), 7.8561 (7), 9.668 (3)
β (°)	94.790 (17)
V (Å³)	849.9 (4)
Z	2
Radiation type	Cu Kα
µ (mm⁻¹)	0.69
Crystal size (mm)	0.30 × 0.30 × 0.18

Data collection
Diffractometer	Enraf–Nonius CAD-4 diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	1716, 1612, 1410
R_int	0.029
(sin θ/λ)_max (Å⁻¹)	0.610

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.049, 0.152, 1.10
No. of reflections	1612
No. of parameters	120
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	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

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