Literature DB >> 26029404

Crystal structure of (E)-N-(3,3-di-phenyl-allyl-idene)-9-ethyl-9H-carbazol-3-amine.

Kannan Thirumurthy1, Ganesamoorthy Thirunarayanan1, S Murugavel2.   

Abstract

In the title compound, C29H24N2, the C=N bond of the central imine group adopts an E conformation. The dihedral angles between the mean plane of the essentially planar carbazole ring system [r.m.s. deviation = 0.039 (2) Å] and the two phenyl rings of the 3,3-di-phenyl-allyl-idene unit are 75.9 (1) and 64.6 (1)°. In the crystal, mol-ecules are linked by C-H⋯π inter-actions, forming a three-dimensional supra-molecular network.

Entities:  

Keywords:  9-ethyl-9H-carbazol-3-amine; C—H⋯π inter­actions; carbazole; crystal structure

Year:  2015        PMID: 26029404      PMCID: PMC4438789          DOI: 10.1107/S2056989015005770

Source DB:  PubMed          Journal:  Acta Crystallogr E Crystallogr Commun


Chemical context

Carbazole and its derivatives have become quite attractive compounds owing to their applications in pharmacy and mol­ecular electronics. It has been reported that carbazole derivatives possess various biological activities, such as anti­tumor (Itoigawa et al., 2000 ▸), anti-oxidative (Tachibana et al., 2001 ▸), anti-inflammatory and anti­mutagenic (Ramsewak et al., 1999 ▸). Carbazole derivatives also exhibit electroactivity and luminescence properties and are considered to be potential candidates for electronic devices such as colour displays, organic semiconductor lasers and solar cells (Friend et al., 1999 ▸). These compounds are thermally and photochemically stable, which makes them useful materials for technological applications. For instance, the carbazole ring is easily funtion­alized and covalently linked to other mol­ecules (Díaz et al., 2002 ▸). This enables its use as a convenient building block for the design and synthesis of mol­ecular glasses, which are widely studied as components of electroactive and photoactive materials (Zhang et al., 2004 ▸). Against this background, and in order to obtain detailed information on mol­ecular conformations in the solid state, X-ray studies of the title compound have been carried out.

Structural commentary

The mol­ecular structure of the title compound is illustrated in Fig. 1 ▸. The C15=N2 bond of the central imine group adopts an E conformation. The carbazole ring system (N1/C1–C12) is essentially planar [maximum deviation = 0.039 (2) Å for atom C9]. The phenyl rings C18C23 and C24–C29 of the (3,3-di­phenyl­allyl­idene) unit are oriented at dihedral angles of 75.9 (1) and 64.6 (1)°, respectively, to the mean plane of the carbazole ring system. The dihedral angle between the two phenyl rings is 76.1 (1)°. The sum of the bond angles around atom N1 (359.7°) of the pyrrole ring is in accordance with sp 2 hybridization. The geometric parameters of the title mol­ecule agree well with those reported for similar structures (Murugavel et al., 2009 ▸; Archana et al., 2011 ▸).
Figure 1

Mol­ecular structure of the title compound with the atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Supra­molecular features

In the crystal, mol­ecules are linked by six inter­molecular C—H⋯π inter­actions, forming a three-dimensional supra­molecular network (Table 1 ▸ and Fig. 2 ▸). Four of these inter­actions involves a benzene H atom of the carbazole ring system and a benzene ring of an adjacent mol­ecule, viz. C7—H7⋯Cg1i, C11—H11⋯Cg3ii, C20—H20⋯Cg4iv, and C29—H29⋯Cg3v. The other two involve a benzene H atom of the carbazole ring system and the pyrrole ring of an adjacent mol­ecule (C8—H8⋯Cg2i), and a methyl­ene H atom of the ethyl group and a benzene ring of an adjacent mol­ecule (C13—H13A⋯Cg1iii); see Table 1 ▸ and Fig. 2 ▸ for full details.
Table 1

Hydrogen-bond geometry (, )

Cg1, Cg2, Cg3 and Cg4 are the centroids of rings C3/C4/C9C12, N1/C1C4, C18C23 and C1/C2/C5C8, respectively.

DHA DHHA D A DHA
C7H7Cg1i 0.932.923.647(2)136
C8H8Cg2i 0.932.983.777(2)145
C11H11Cg3ii 0.932.853.551(2)133
C13H13A Cg1iii 0.973.003.749(2)135
C20H20Cg4iv 0.932.623.498(2)157
C29H29Cg3v 0.932.873.796(3)175

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) .

Figure 2

A partial view along the b axis of the crystal packing of the title compound, showing the inter­molecular C—H⋯π inter­actions (see Table 1 ▸ for details), forming a three-dimensional supra­molecular network. H atoms not involved in these inter­actions have been omitted for clarity.

Synthesis and crystallization

A 25 ml round-bottom flask was charged with 9-ethyl-9H-carbazol-3-amine (1 mmol), 3,3-di­phenyl­acryl­aldehyde (1 mmol) and sulfated SnO2-Bi2O3-fly ash catalyst (20 mg) in water (15 ml) and the mixture was refluxed at 363 K for 1h. On completion of the reaction (monitored by TLC with ethyl acetate and hexane as an eluent 20%) the mixture was cooled to ambient temperature. Di­chloro­methane (20 ml) was then added to separate the organic and aqueous layers. The organic layer was filtered, dried on anhydrous Na2SO4 and the solvent removed using a rotary evaporator. The crude product obtained was purified by column chromatography on silica gel (200 mesh) with hexane and ethyl acetate (4:1) as eluent, to afford the title compound in good yield (93%). Red crystals suitable for X-ray diffraction analysis were obtained after recrystallization in CH2Cl2.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. H atoms were positioned geometrically and constrained to ride on their parent atom with C—H = 0.93–0.97 Å and with U iso(H) = 1.5U eq for methyl H atoms and 1.2U eq(C) for other H atoms.
Table 2

Experimental details

Crystal data
Chemical formulaC29H24N2
M r 400.50
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c ()13.6502(17), 8.7616(13), 18.224(2)
()92.234(11)
V (3)2177.9(5)
Z 4
Radiation typeMo K
(mm1)0.07
Crystal size (mm)0.23 0.21 0.15
 
Data collection
DiffractometerBruker SMART CCD area detector
Absorption correctionMulti-scan (SADABS; Sheldrick, 1996)
T min, T max 0.984, 0.989
No. of measured, independent and observed [I > 2(I)] reflections9709, 4982, 3066
R int 0.047
(sin /)max (1)0.688
 
Refinement
R[F 2 > 2(F 2)], wR(F 2), S 0.056, 0.150, 1.03
No. of reflections4982
No. of parameters280
H-atom treatmentH-atom parameters constrained
max, min (e 3)0.17, 0.19

Computer programs: SMART and SAINT (Bruker, 2002 ▸), SHELXS97 and SHELXL97 (Sheldrick, 2008 ▸), ORTEP-3 for Windows (Farrugia (2012 ▸) and PLATON (Spek, 2009 ▸).

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S2056989015005770/su5095sup1.cif Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015005770/su5095Isup2.hkl CCDC reference: 967497 Additional supporting information: crystallographic information; 3D view; checkCIF report
C29H24N2F(000) = 848
Mr = 400.50Dx = 1.221 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 5927 reflections
a = 13.6502 (17) Åθ = 2.8–29.3°
b = 8.7616 (13) ŵ = 0.07 mm1
c = 18.224 (2) ÅT = 293 K
β = 92.234 (11)°Block, red
V = 2177.9 (5) Å30.23 × 0.21 × 0.15 mm
Z = 4
Bruker SMART CCD area-detector diffractometer4982 independent reflections
Radiation source: fine-focus sealed tube3066 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.047
φ and ω scansθmax = 29.3°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)h = −15→18
Tmin = 0.984, Tmax = 0.989k = −11→11
9709 measured reflectionsl = −24→23
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.056Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.150H-atom parameters constrained
S = 1.03w = 1/[σ2(Fo2) + (0.0555P)2 + 0.1709P] where P = (Fo2 + 2Fc2)/3
4982 reflections(Δ/σ)max < 0.001
280 parametersΔρmax = 0.17 e Å3
0 restraintsΔρmin = −0.19 e Å3
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.
xyzUiso*/Ueq
C140.5899 (2)1.3222 (3)0.14013 (13)0.0822 (7)
H14A0.61921.41320.12150.123*
H14B0.61441.30410.18940.123*
H14C0.52001.33460.13990.123*
N20.19996 (10)0.8129 (2)0.10030 (8)0.0516 (4)
C100.29431 (12)0.8778 (2)0.09957 (9)0.0454 (4)
C90.36711 (12)0.8093 (2)0.14234 (9)0.0449 (4)
H90.35380.72260.16960.054*
C40.47794 (13)1.0054 (2)0.10553 (9)0.0462 (4)
C30.46026 (12)0.8713 (2)0.14420 (9)0.0427 (4)
N10.57338 (11)1.04985 (18)0.11800 (8)0.0530 (4)
C120.40455 (14)1.0746 (2)0.06391 (10)0.0530 (5)
H120.41661.16360.03800.064*
C110.31382 (14)1.0100 (2)0.06153 (10)0.0518 (5)
H110.26361.05600.03360.062*
C19−0.16510 (13)0.7140 (2)0.04772 (10)0.0533 (5)
H19−0.13690.76910.08670.064*
C150.14631 (13)0.8153 (2)0.04164 (10)0.0529 (5)
H150.17140.8548−0.00110.063*
C20.55154 (13)0.8316 (2)0.18155 (9)0.0455 (4)
C18−0.11167 (13)0.6882 (2)−0.01430 (10)0.0471 (4)
C10.61869 (13)0.9460 (2)0.16451 (10)0.0510 (5)
C160.04842 (13)0.7586 (3)0.04026 (10)0.0553 (5)
H160.02300.73190.08510.066*
C23−0.15719 (14)0.6089 (2)−0.07131 (11)0.0588 (5)
H23−0.12350.5911−0.11390.071*
C20−0.25842 (14)0.6598 (3)0.05254 (12)0.0614 (6)
H20−0.29300.67720.09470.074*
C240.02709 (12)0.7604 (2)−0.09425 (9)0.0477 (5)
C130.61468 (15)1.1902 (2)0.09293 (11)0.0614 (5)
H13A0.59061.20990.04300.074*
H13B0.68541.18000.09230.074*
C80.58185 (14)0.7119 (2)0.22603 (10)0.0550 (5)
H80.53850.63430.23740.066*
C290.10181 (14)0.6715 (3)−0.11811 (11)0.0592 (5)
H290.13140.6011−0.08620.071*
C280.13409 (15)0.6844 (3)−0.18854 (13)0.0714 (7)
H280.18460.6220−0.20370.086*
C50.71384 (14)0.9426 (3)0.19254 (11)0.0666 (6)
H50.75801.01940.18170.080*
C22−0.25053 (16)0.5561 (3)−0.06653 (13)0.0688 (6)
H22−0.28000.5034−0.10580.083*
C25−0.01406 (15)0.8636 (3)−0.14288 (11)0.0639 (6)
H25−0.06550.9249−0.12840.077*
C21−0.30082 (16)0.5802 (3)−0.00460 (13)0.0675 (6)
H21−0.36410.5423−0.00120.081*
C270.09292 (18)0.7869 (3)−0.23570 (12)0.0767 (7)
H270.11450.7952−0.28330.092*
C60.74105 (16)0.8237 (3)0.23656 (12)0.0746 (7)
H60.80500.81960.25600.089*
C260.01946 (18)0.8779 (3)−0.21270 (12)0.0784 (7)
H26−0.00830.9503−0.24450.094*
C70.67657 (16)0.7091 (3)0.25318 (11)0.0699 (6)
H70.69770.62890.28320.084*
C17−0.00988 (13)0.7403 (2)−0.01930 (9)0.0478 (4)
U11U22U33U12U13U23
C140.116 (2)0.0536 (15)0.0788 (15)−0.0230 (14)0.0288 (14)−0.0040 (12)
N20.0456 (9)0.0658 (12)0.0433 (8)0.0018 (8)−0.0019 (7)−0.0031 (8)
C100.0456 (10)0.0533 (12)0.0372 (9)0.0019 (8)0.0004 (7)−0.0053 (8)
C90.0533 (11)0.0435 (11)0.0377 (9)−0.0022 (8)−0.0017 (8)−0.0005 (8)
C40.0522 (11)0.0419 (11)0.0444 (9)0.0002 (8)0.0019 (8)−0.0038 (8)
C30.0499 (10)0.0401 (10)0.0380 (9)0.0004 (8)−0.0001 (7)−0.0022 (8)
N10.0532 (9)0.0478 (10)0.0578 (9)−0.0083 (8)0.0017 (7)−0.0004 (8)
C120.0614 (12)0.0441 (12)0.0535 (11)0.0019 (9)0.0023 (9)0.0054 (9)
C110.0568 (11)0.0526 (12)0.0455 (10)0.0101 (9)−0.0034 (8)0.0013 (9)
C190.0526 (11)0.0567 (13)0.0504 (10)0.0044 (9)−0.0021 (8)0.0045 (9)
C150.0484 (10)0.0683 (14)0.0418 (10)0.0015 (9)−0.0006 (8)−0.0023 (9)
C20.0482 (10)0.0488 (11)0.0393 (9)0.0001 (8)0.0002 (7)−0.0041 (8)
C180.0471 (10)0.0461 (11)0.0474 (10)0.0048 (8)−0.0057 (8)0.0054 (8)
C10.0532 (11)0.0524 (12)0.0472 (10)−0.0032 (9)−0.0009 (8)−0.0064 (9)
C160.0472 (10)0.0735 (15)0.0451 (10)0.0008 (10)−0.0007 (8)0.0036 (10)
C230.0559 (12)0.0603 (14)0.0596 (12)0.0007 (10)−0.0046 (9)−0.0024 (10)
C200.0531 (12)0.0642 (15)0.0671 (13)0.0050 (10)0.0057 (10)0.0154 (11)
C240.0446 (10)0.0522 (12)0.0459 (10)0.0039 (9)−0.0039 (8)−0.0050 (9)
C130.0704 (13)0.0566 (14)0.0584 (12)−0.0141 (11)0.0164 (10)0.0004 (10)
C80.0571 (11)0.0621 (14)0.0456 (10)0.0048 (10)0.0005 (8)0.0032 (9)
C290.0545 (12)0.0603 (14)0.0626 (12)0.0056 (10)0.0008 (9)−0.0078 (10)
C280.0530 (12)0.0880 (19)0.0741 (15)−0.0027 (12)0.0132 (11)−0.0268 (14)
C50.0539 (12)0.0804 (17)0.0649 (13)−0.0121 (11)−0.0057 (10)−0.0085 (12)
C220.0697 (14)0.0616 (15)0.0738 (14)−0.0076 (11)−0.0155 (12)−0.0035 (12)
C250.0635 (13)0.0712 (15)0.0568 (12)0.0143 (11)−0.0012 (10)0.0049 (11)
C210.0553 (12)0.0585 (15)0.0879 (16)−0.0069 (10)−0.0070 (12)0.0194 (13)
C270.0734 (15)0.108 (2)0.0490 (12)−0.0204 (15)0.0074 (11)−0.0124 (13)
C60.0600 (13)0.101 (2)0.0610 (13)0.0021 (13)−0.0172 (11)−0.0034 (14)
C260.0879 (17)0.092 (2)0.0542 (13)0.0018 (15)−0.0057 (12)0.0154 (13)
C70.0667 (14)0.0886 (18)0.0534 (12)0.0103 (13)−0.0094 (10)0.0095 (12)
C170.0488 (10)0.0488 (12)0.0454 (10)0.0066 (9)−0.0037 (8)0.0012 (9)
C14—C131.488 (3)C18—C231.378 (3)
N2—C151.272 (2)C18—C171.469 (2)
N2—C101.408 (2)C1—C51.377 (3)
C10—C91.376 (2)C16—C171.330 (2)
C10—C111.381 (3)C23—C221.361 (3)
C9—C31.382 (2)C20—C211.364 (3)
C4—N11.370 (2)C24—C291.367 (3)
C4—C121.374 (2)C24—C251.371 (3)
C4—C31.396 (3)C24—C171.485 (2)
C3—C21.439 (2)C8—C71.367 (3)
N1—C11.374 (2)C29—C281.378 (3)
N1—C131.435 (2)C28—C271.351 (3)
C12—C111.361 (3)C5—C61.358 (3)
C19—C201.365 (3)C22—C211.360 (3)
C19—C181.387 (3)C25—C261.375 (3)
C15—C161.425 (2)C27—C261.360 (3)
C2—C81.379 (3)C6—C71.377 (3)
C2—C11.401 (3)
C15—N2—C10118.81 (16)N1—C1—C5129.66 (19)
C9—C10—C11120.03 (17)N1—C1—C2109.14 (15)
C9—C10—N2117.33 (17)C5—C1—C2121.20 (19)
C11—C10—N2122.53 (16)C17—C16—C15125.96 (18)
C10—C9—C3119.10 (17)C22—C23—C18121.2 (2)
N1—C4—C12129.36 (18)C21—C20—C19119.9 (2)
N1—C4—C3109.73 (15)C29—C24—C25117.50 (18)
C12—C4—C3120.90 (17)C29—C24—C17120.63 (17)
C9—C3—C4119.69 (16)C25—C24—C17121.82 (17)
C9—C3—C2134.08 (17)N1—C13—C14112.39 (17)
C4—C3—C2106.19 (16)C7—C8—C2119.0 (2)
C4—N1—C1108.43 (15)C24—C29—C28121.3 (2)
C4—N1—C13125.00 (17)C27—C28—C29120.4 (2)
C1—N1—C13126.23 (16)C6—C5—C1117.9 (2)
C11—C12—C4118.49 (18)C21—C22—C23120.3 (2)
C12—C11—C10121.74 (17)C24—C25—C26121.0 (2)
C20—C19—C18121.14 (19)C22—C21—C20120.0 (2)
N2—C15—C16121.17 (18)C28—C27—C26119.2 (2)
C8—C2—C1119.35 (17)C5—C6—C7121.8 (2)
C8—C2—C3134.14 (18)C27—C26—C25120.5 (2)
C1—C2—C3106.50 (16)C8—C7—C6120.7 (2)
C23—C18—C19117.43 (18)C16—C17—C18121.61 (17)
C23—C18—C17120.66 (17)C16—C17—C24121.49 (17)
C19—C18—C17121.91 (16)C18—C17—C24116.75 (15)
C15—N2—C10—C9−145.48 (18)N2—C15—C16—C17−172.1 (2)
C15—N2—C10—C1138.4 (3)C19—C18—C23—C22−0.9 (3)
C11—C10—C9—C3−2.6 (3)C17—C18—C23—C22178.05 (19)
N2—C10—C9—C3−178.80 (15)C18—C19—C20—C21−0.7 (3)
C10—C9—C3—C42.9 (2)C4—N1—C13—C1479.5 (2)
C10—C9—C3—C2179.98 (18)C1—N1—C13—C14−93.1 (2)
N1—C4—C3—C9177.03 (15)C1—C2—C8—C70.8 (3)
C12—C4—C3—C9−1.8 (3)C3—C2—C8—C7180.0 (2)
N1—C4—C3—C2−0.8 (2)C25—C24—C29—C28−0.5 (3)
C12—C4—C3—C2−179.66 (16)C17—C24—C29—C28177.20 (19)
C12—C4—N1—C1178.78 (19)C24—C29—C28—C270.7 (3)
C3—C4—N1—C10.1 (2)N1—C1—C5—C6−178.4 (2)
C12—C4—N1—C135.1 (3)C2—C1—C5—C60.8 (3)
C3—C4—N1—C13−173.63 (17)C18—C23—C22—C21−0.4 (3)
N1—C4—C12—C11−178.20 (17)C29—C24—C25—C26−0.6 (3)
C3—C4—C12—C110.4 (3)C17—C24—C25—C26−178.3 (2)
C4—C12—C11—C10−0.1 (3)C23—C22—C21—C201.2 (3)
C9—C10—C11—C121.2 (3)C19—C20—C21—C22−0.6 (3)
N2—C10—C11—C12177.20 (17)C29—C28—C27—C260.3 (3)
C10—N2—C15—C16−176.66 (18)C1—C5—C6—C70.0 (3)
C9—C3—C2—C84.6 (3)C28—C27—C26—C25−1.4 (4)
C4—C3—C2—C8−178.0 (2)C24—C25—C26—C271.6 (4)
C9—C3—C2—C1−176.15 (19)C2—C8—C7—C60.0 (3)
C4—C3—C2—C11.23 (19)C5—C6—C7—C8−0.5 (4)
C20—C19—C18—C231.4 (3)C15—C16—C17—C18−176.78 (19)
C20—C19—C18—C17−177.52 (18)C15—C16—C17—C247.9 (3)
C4—N1—C1—C5−179.9 (2)C23—C18—C17—C16−152.0 (2)
C13—N1—C1—C5−6.3 (3)C19—C18—C17—C1626.9 (3)
C4—N1—C1—C20.8 (2)C23—C18—C17—C2423.6 (3)
C13—N1—C1—C2174.34 (17)C19—C18—C17—C24−157.54 (18)
C8—C2—C1—N1178.13 (16)C29—C24—C17—C1659.9 (3)
C3—C2—C1—N1−1.2 (2)C25—C24—C17—C16−122.5 (2)
C8—C2—C1—C5−1.3 (3)C29—C24—C17—C18−115.7 (2)
C3—C2—C1—C5179.36 (17)C25—C24—C17—C1861.9 (3)
D—H···AD—HH···AD···AD—H···A
C7—H7···Cg1i0.932.923.647 (2)136
C8—H8···Cg2i0.932.983.777 (2)145
C11—H11···Cg3ii0.932.853.551 (2)133
C13—H13A···Cg1iii0.973.003.749 (2)135
C20—H20···Cg4iv0.932.623.498 (2)157
C29—H29···Cg3v0.932.873.796 (3)175
  7 in total

1.  A short history of SHELX.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr A       Date:  2007-12-21       Impact factor: 2.290

2.  Antioxidative activity of carbazoles from Murraya koenigii leaves.

Authors:  Y Tachibana; H Kikuzaki; N H Lajis; N Nakatani
Journal:  J Agric Food Chem       Date:  2001-11       Impact factor: 5.279

3.  Biologically active carbazole alkaloids from Murraya koenigii.

Authors:  R S Ramsewak; M G Nair; G M Strasburg; D L DeWitt; J L Nitiss
Journal:  J Agric Food Chem       Date:  1999-02       Impact factor: 5.279

4.  Antitumor agents. 203. Carbazole alkaloid murrayaquinone A and related synthetic carbazolequinones as cytotoxic agents.

Authors:  M Itoigawa; Y Kashiwada; C Ito; H Furukawa; Y Tachibana; K F Bastow; K H Lee
Journal:  J Nat Prod       Date:  2000-07       Impact factor: 4.050

5.  3-[2-(9-Ethyl-9H-carbazol-3-yl)-6-methyl-3-quinol-yl]propan-1-ol.

Authors:  S Murugavel; S Ranjith; A Subbiahpandi; G Periyasami; R Raghunathan
Journal:  Acta Crystallogr Sect E Struct Rep Online       Date:  2008-12-17

6.  9-Ethyl-N-(3-nitro-benzyl-idene)-9H-carbazol-3-amine.

Authors:  R Archana; E Yamuna; K J Rajendra Prasad; A Thiruvalluvar; R J Butcher
Journal:  Acta Crystallogr Sect E Struct Rep Online       Date:  2011-06-25

7.  Structure validation in chemical crystallography.

Authors:  Anthony L Spek
Journal:  Acta Crystallogr D Biol Crystallogr       Date:  2009-01-20
  7 in total

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