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

Abstract

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,

• a = 11.229 (4) Å

• b = 7.8561 (7) Å

• c = 9.668 (3) Å

• β = 94.790 (17)°

• V = 849.9 (4) ų

• 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[F ² > 2σ(F ²)] = 0.049

• wR(F ²) = 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.

Supplementary Material

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

supplementary crystallographic information

Comment

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).

Experimental

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.

Refinement

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 U_eq of the parent atom.

Figures

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.

Crystal data

C22H20N2O2	F(000) = 364
Mr = 344.40	Dx = 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

Enraf–Nonius CAD-4 diffractometer	Rint = 0.029
Radiation source: rotating anode	θmax = 70.0°, θmin = 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

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(Fo2) + (0.0969P)2 + 0.1743P] where P = (Fo2 + 2Fc2)/3
1612 reflections	(Δ/σ)max < 0.001
120 parameters	Δρmax = 0.25 e Å−3
0 restraints	Δρmin = −0.27 e Å−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
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 (Ų)

	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)

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.