3-Chloro-3-(9-ethyl-6-methyl-9H-carbazol-3-yl)propenal

The carbazole moiety of the title mol­ecule, C₁₈H₁₆ClNO, is planar to within 0.020 (2) Å. The 3-chloro­propenal substituent is coplanar with the carbazole ring system, whereas the N-ethyl substituent is inclined to it by 87.7 (2)°. The crystal packing is stabilized by weak π–π interactions, C—H...Cl interactions and van der Waals forces.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.048
• wR factor = 0.130
• Data-to-parameter ratio = 17.0

checkCIF/PLATON results

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PLAT029_ALERT_3_A _diffrn_measured_fraction_theta_full Low .....       0.98

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S1. Comment

The bioactive carbazole ring system present in a number of natural products (Nakahara et al., 2002) is responsible for their antimycobacterial, antifungal (Sunthitikawinsakul et al., 2003), antiosteoporotic (Wang et al., 2003), antitumoral (Martin et al., 2002) and antioxidative (Tachibana et al., 2001) activities. It has been found to have DNA-interclating properties (Neidle, 1979; Aggarwal et al., 1983). Carbazole behaves as a fluorescence carrier for the preparation of doxycycline sensors in pharmaceutical preparations. N-ethyl carbazole derivatives have been used for non-linear optical properties (Nesterov et al., 2002). We report here the structure of the title compound, (I), a carbazole derivative.

The carbazole skeleton in (I) (Fig. 1) is planar to within ±0.020 (2) Å. The 3-chloropropenal substituent is coplanar with the carbazole ring system, with atoms Cl1, O1, C13, C14 and C15 deviating from the carbazole plane by 0.022 (1), 0.014 (2), −0.011 (2), −0.046 (2) and −0.030 (2) Å, respectively. The C1A—N1—C10—C11 torsion angle of 87.7 (2)° shows how the N-ethyl substituent is oriented. The bond lengths and angles observed in (I) (Table 1) agree with those reported for related structures (Hökelek et al., 2001a,b). A short contact between atoms H2 and H14 (2.04 Å) results in the widening of the C3—C13—C14 angle [126.5 (2)°] from the ideal value of 120°.

In addition to van der Waals forces and C—H···Cl interactions (Table 2), the crystal packing (Fig. 2) is stabilized by weak π–π interactions involving ring C. The molecules at (x, y, z) and (-x, 1 − y, 1 − z) are stacked with their C ring centroids separated by 3.751 (1) Å; the interplanar separation is 3.491 Å and the displacement is 1.88 Å (Glidewell et al., 2002).

S2. Experimental

To a stirred mixture of 3-methyl(9-ethyl-6-methylcarbazol) (0.5 g, 1 mmol) in dimethylformamide (7 ml) under ice-cold conditions, POCl₃ (3 mmol) was added and the mixture stirred at room temperature for 30 min. After completion of the reaction, the mixture was poured onto crushed ice, neutralized with sodium hydroxide solution (5%) and extracted with CHCl₃ (3 × 10 ml). The organic layer was separated, dried over anhydrous Na₂SO₄ and distilled under reduced pressure. The residue was then recrystallized from a mixture of ethyl acetate and petroleum ether (2:8) to give the title compound, (I).

S3. Refinement

H atoms were fixed geometrically and allowed to ride on their corresponding parent atoms, with C—H distances fixed in the range 0.93–0.97 Å and with U_iso(H) = 1.5U_eq(parent C) for the methyl H atoms and 1.2U_eq(parent C) for the rest. A rotating group model was used for the methyl groups. Reflections were measured to θ_max of 27.97° with 92% completeness, but the data are 98% complete to 25°.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ZORTEP (Zsolnai, 1997) and PLATON (Spek, 1990); software used to prepare material for publication: SHELXL97 and PARST (Nardelli, 1995).

Figures

	Fig. 1. The structure of (I), showing 35% probability displacement ellipsoids and the atom-numbering scheme.
	Fig. 2. Packing of the molecules of (I), viewed down the b axis.

3-Chloro-3-(9-ethyl-6-methyl-9H-carbazol-3-yl)propenal

Crystal data

C18H16ClNO	Z = 2
Mr = 297.77	F(000) = 312
Triclinic, P1	Dx = 1.334 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.3191 (7) Å	Cell parameters from 1829 reflections
b = 8.9264 (9) Å	θ = 2.5–27.5°
c = 12.2024 (12) Å	µ = 0.26 mm^−1
α = 105.247 (2)°	T = 293 K
β = 91.771 (2)°	Block, yellow
γ = 104.378 (2)°	0.4 × 0.2 × 0.2 mm
V = 741.11 (13) Å^3

Data collection

Siemens SMART CCD area-detector diffractometer	2672 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.015
Graphite monochromator	θmax = 28.0°, θmin = 1.7°
ω scans	h = −9→9
4703 measured reflections	k = −11→11
3269 independent reflections	l = −15→11

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.130	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0636P)^2 + 0.1889P] where P = (Fo^2 + 2Fc^2)/3
3269 reflections	(Δ/σ)max = 0.002
192 parameters	Δρmax = 0.22 e Å^−3
0 restraints	Δρmin = −0.23 e Å^−3

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 (Ų)

	x	y	z	Uiso*/Ueq
Cl1	0.29248 (8)	0.36763 (6)	0.22958 (4)	0.05956 (19)
C3	0.1870 (2)	0.3345 (2)	0.43559 (14)	0.0409 (4)
C4A	0.2524 (2)	0.5765 (2)	0.59199 (14)	0.0387 (4)
N1	0.1805 (2)	0.58443 (19)	0.77307 (12)	0.0462 (4)
C5A	0.3126 (2)	0.7420 (2)	0.66139 (14)	0.0407 (4)
C4	0.2586 (2)	0.5004 (2)	0.47764 (14)	0.0397 (4)
H4	0.3106	0.5608	0.4291	0.048*
C13	0.1879 (2)	0.2487 (2)	0.31532 (15)	0.0428 (4)
C1A	0.1731 (3)	0.4845 (2)	0.66539 (14)	0.0421 (4)
C8A	0.2669 (3)	0.7407 (2)	0.77223 (15)	0.0425 (4)
C14	0.1174 (3)	0.0911 (2)	0.26654 (18)	0.0579 (5)
H14	0.0596	0.0304	0.3135	0.069*
C2	0.1097 (3)	0.2465 (2)	0.51167 (17)	0.0536 (5)
H2	0.0621	0.1353	0.4838	0.064*
C8	0.3092 (3)	0.8816 (2)	0.86172 (16)	0.0516 (5)
H8	0.2788	0.8802	0.9349	0.062*
C5	0.4012 (3)	0.8878 (2)	0.64073 (16)	0.0473 (4)
H5	0.4307	0.8901	0.5675	0.057*
C1	0.1019 (3)	0.3182 (2)	0.62487 (17)	0.0538 (5)
H1	0.0504	0.2574	0.6732	0.065*
O1	0.0638 (3)	−0.1403 (2)	0.11213 (15)	0.0904 (6)
C7	0.3974 (3)	1.0232 (2)	0.83830 (17)	0.0559 (5)
H7	0.4262	1.1185	0.8972	0.067*
C10	0.1243 (3)	0.5343 (3)	0.87411 (16)	0.0530 (5)
H10A	0.0187	0.4383	0.8518	0.064*
H10B	0.0816	0.6186	0.9259	0.064*
C6	0.4456 (3)	1.0291 (2)	0.72885 (17)	0.0531 (5)
C15	0.1207 (3)	0.0042 (3)	0.14920 (19)	0.0658 (6)
H15	0.1696	0.0630	0.0992	0.079*
C11	0.2840 (3)	0.4999 (3)	0.93519 (19)	0.0727 (7)
H11A	0.3220	0.4125	0.8856	0.109*
H11B	0.2424	0.4710	1.0025	0.109*
H11C	0.3896	0.5941	0.9564	0.109*
C12	0.5468 (4)	1.1878 (3)	0.7089 (2)	0.0743 (7)
H12A	0.6410	1.1713	0.6573	0.111*
H12B	0.6069	1.2626	0.7802	0.111*
H12C	0.4568	1.2304	0.6765	0.111*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0879 (4)	0.0482 (3)	0.0404 (3)	0.0143 (2)	0.0143 (2)	0.0114 (2)
C3	0.0451 (9)	0.0372 (9)	0.0388 (9)	0.0102 (7)	0.0037 (7)	0.0088 (7)
C4A	0.0415 (9)	0.0366 (8)	0.0371 (9)	0.0093 (7)	0.0036 (7)	0.0095 (7)
N1	0.0543 (9)	0.0470 (8)	0.0343 (7)	0.0087 (7)	0.0087 (6)	0.0105 (6)
C5A	0.0445 (9)	0.0398 (9)	0.0370 (9)	0.0124 (7)	0.0039 (7)	0.0084 (7)
C4	0.0453 (9)	0.0373 (9)	0.0353 (8)	0.0093 (7)	0.0049 (7)	0.0100 (7)
C13	0.0459 (10)	0.0397 (9)	0.0416 (9)	0.0127 (7)	0.0038 (7)	0.0083 (7)
C1A	0.0461 (9)	0.0422 (9)	0.0365 (9)	0.0095 (7)	0.0052 (7)	0.0104 (7)
C8A	0.0446 (9)	0.0434 (9)	0.0390 (9)	0.0134 (7)	0.0059 (7)	0.0089 (7)
C14	0.0732 (14)	0.0451 (11)	0.0475 (11)	0.0097 (10)	0.0121 (9)	0.0044 (8)
C2	0.0720 (13)	0.0348 (9)	0.0478 (11)	0.0051 (9)	0.0057 (9)	0.0096 (8)
C8	0.0626 (12)	0.0519 (11)	0.0371 (9)	0.0168 (9)	0.0071 (8)	0.0051 (8)
C5	0.0597 (11)	0.0400 (9)	0.0387 (9)	0.0095 (8)	0.0058 (8)	0.0086 (7)
C1	0.0694 (13)	0.0436 (10)	0.0452 (10)	0.0040 (9)	0.0103 (9)	0.0166 (8)
O1	0.1218 (16)	0.0490 (9)	0.0731 (11)	0.0041 (9)	0.0213 (10)	−0.0129 (8)
C7	0.0701 (13)	0.0442 (10)	0.0444 (10)	0.0153 (9)	0.0018 (9)	−0.0027 (8)
C10	0.0610 (12)	0.0584 (12)	0.0383 (10)	0.0102 (9)	0.0151 (8)	0.0158 (8)
C6	0.0659 (12)	0.0388 (10)	0.0494 (11)	0.0112 (9)	0.0025 (9)	0.0063 (8)
C15	0.0795 (15)	0.0504 (12)	0.0539 (12)	0.0109 (11)	0.0107 (11)	−0.0030 (9)
C11	0.0781 (16)	0.0948 (18)	0.0527 (13)	0.0201 (14)	0.0099 (11)	0.0355 (12)
C12	0.1058 (19)	0.0407 (11)	0.0645 (14)	0.0046 (12)	0.0090 (13)	0.0086 (10)

Geometric parameters (Å, º)

Cl1—C13	1.743 (2)	C8—C7	1.375 (3)
C3—C4	1.389 (2)	C8—H8	0.93
C3—C2	1.412 (2)	C5—C6	1.384 (3)
C3—C13	1.467 (2)	C5—H5	0.93
C4A—C4	1.389 (2)	C1—H1	0.93
C4A—C1A	1.412 (2)	O1—C15	1.207 (3)
C4A—C5A	1.445 (2)	C7—C6	1.403 (3)
N1—C1A	1.371 (2)	C7—H7	0.93
N1—C8A	1.384 (2)	C10—C11	1.504 (3)
N1—C10	1.456 (2)	C10—H10A	0.97
C5A—C5	1.394 (2)	C10—H10B	0.97
C5A—C8A	1.405 (2)	C6—C12	1.513 (3)
C4—H4	0.93	C15—H15	0.93
C13—C14	1.334 (3)	C11—H11A	0.96
C1A—C1	1.390 (3)	C11—H11B	0.96
C8A—C8	1.391 (3)	C11—H11C	0.96
C14—C15	1.442 (3)	C12—H12A	0.96
C14—H14	0.93	C12—H12B	0.96
C2—C1	1.371 (3)	C12—H12C	0.96
C2—H2	0.93
C4—C3—C2	118.5 (2)	C6—C5—C5A	120.2 (2)
C4—C3—C13	122.3 (2)	C6—C5—H5	119.9
C2—C3—C13	119.3 (2)	C5A—C5—H5	119.9
C4—C4A—C1A	119.8 (2)	C2—C1—C1A	118.1 (2)
C4—C4A—C5A	134.0 (2)	C2—C1—H1	120.9
C1A—C4A—C5A	106.2 (1)	C1A—C1—H1	120.9
C1A—N1—C8A	108.5 (1)	C8—C7—C6	122.4 (2)
C1A—N1—C10	126.1 (2)	C8—C7—H7	118.8
C8A—N1—C10	125.2 (2)	C6—C7—H7	118.8
C5—C5A—C8A	119.2 (2)	N1—C10—C11	112.2 (2)
C5—C5A—C4A	134.4 (2)	N1—C10—H10A	109.2
C8A—C5A—C4A	106.4 (2)	C11—C10—H10A	109.2
C3—C4—C4A	120.1 (2)	N1—C10—H10B	109.2
C3—C4—H4	119.9	C11—C10—H10B	109.2
C4A—C4—H4	119.9	H10A—C10—H10B	107.9
C14—C13—C3	126.5 (2)	C5—C6—C7	119.0 (2)
C14—C13—Cl1	117.8 (2)	C5—C6—C12	121.0 (2)
C3—C13—Cl1	115.6 (1)	C7—C6—C12	120.0 (2)
N1—C1A—C1	129.6 (2)	O1—C15—C14	123.9 (2)
N1—C1A—C4A	109.6 (2)	O1—C15—H15	118.1
C1—C1A—C4A	120.8 (2)	C14—C15—H15	118.1
N1—C8A—C8	129.2 (2)	C10—C11—H11A	109.5
N1—C8A—C5A	109.4 (2)	C10—C11—H11B	109.5
C8—C8A—C5A	121.4 (2)	H11A—C11—H11B	109.5
C13—C14—C15	127.3 (2)	C10—C11—H11C	109.5
C13—C14—H14	116.3	H11A—C11—H11C	109.5
C15—C14—H14	116.3	H11B—C11—H11C	109.5
C1—C2—C3	122.7 (2)	C6—C12—H12A	109.5
C1—C2—H2	118.7	C6—C12—H12B	109.5
C3—C2—H2	118.7	H12A—C12—H12B	109.5
C7—C8—C8A	117.8 (2)	C6—C12—H12C	109.5
C7—C8—H8	121.1	H12A—C12—H12C	109.5
C8A—C8—H8	121.1	H12B—C12—H12C	109.5
C4—C4A—C5A—C5	−0.9 (4)	C5—C5A—C8A—N1	180.0 (2)
C1A—C4A—C5A—C5	179.2 (2)	C4A—C5A—C8A—N1	−0.8 (2)
C4—C4A—C5A—C8A	−179.9 (2)	C5—C5A—C8A—C8	−0.3 (3)
C1A—C4A—C5A—C8A	0.2 (2)	C4A—C5A—C8A—C8	178.9 (2)
C2—C3—C4—C4A	−0.3 (3)	C3—C13—C14—C15	−178.5 (2)
C13—C3—C4—C4A	179.2 (2)	Cl1—C13—C14—C15	1.5 (3)
C1A—C4A—C4—C3	−0.1 (3)	C4—C3—C2—C1	0.2 (3)
C5A—C4A—C4—C3	180.0 (2)	C13—C3—C2—C1	−179.3 (2)
C4—C3—C13—C14	−177.8 (2)	N1—C8A—C8—C7	179.7 (2)
C2—C3—C13—C14	1.7 (3)	C5A—C8A—C8—C7	0.1 (3)
C4—C3—C13—Cl1	2.3 (2)	C8A—C5A—C5—C6	0.8 (3)
C2—C3—C13—Cl1	−178.3 (1)	C4A—C5A—C5—C6	−178.1 (2)
C8A—N1—C1A—C1	179.1 (2)	C3—C2—C1—C1A	0.1 (3)
C10—N1—C1A—C1	4.5 (3)	N1—C1A—C1—C2	179.3 (2)
C8A—N1—C1A—C4A	−1.1 (2)	C4A—C1A—C1—C2	−0.5 (3)
C10—N1—C1A—C4A	−175.7 (2)	C8A—C8—C7—C6	−0.2 (3)
C4—C4A—C1A—N1	−179.4 (2)	C1A—N1—C10—C11	87.7 (2)
C5A—C4A—C1A—N1	0.6 (2)	C8A—N1—C10—C11	−86.0 (2)
C4—C4A—C1A—C1	0.4 (3)	C5A—C5—C6—C7	−0.9 (3)
C5A—C4A—C1A—C1	−179.6 (2)	C5A—C5—C6—C12	178.2 (2)
C1A—N1—C8A—C8	−178.4 (2)	C8—C7—C6—C5	0.7 (3)
C10—N1—C8A—C8	−3.8 (3)	C8—C7—C6—C12	−178.5 (2)
C1A—N1—C8A—C5A	1.2 (2)	C13—C14—C15—O1	175.5 (2)
C10—N1—C8A—C5A	175.8 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···Cl1	0.93	2.57	2.989 (2)	108
C15—H15···Cl1	0.93	2.68	3.048 (2)	105