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1H-Indole-3-carbaldehyde azine

aDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
*Correspondence e-mail: seikweng@um.edu.my

(Received 22 January 2008; accepted 28 January 2008; online 6 February 2008)

The molecule of the title compound, C18H14N4, lies on a center of inversion such that there is one half-mol­ecule in the asymmetric unit. The N—N single bond adopts a trans configuration and the indole fused-ring system is nearly coplanar with the –CH=N—N=CH– fragment [dihedral angle = 9.8 (2)°]. Adjacent mol­ecules are linked by indole–azine N—H⋯N hydrogen bonds into a layer motif.

Related literature

For the synthesis, see: Alemany et al. (1970[Alemany, A., Bernabe, M., Fernandez Alvarez, E., Lora-Tamayo, M. & Nieto Lopez, O. (1970). Anal. Quim. 66, 681-688.]); Swaminathan & Narasimhan (1964[Swaminathan, S. & Narasimhan, K. (1964). Indian J. Chem. 2, 423-424.]). For the crystal structures of some aromatic azines, for example, benzalazine, see: Burke-Laing & Laing (1976[Burke-Laing, M. & Laing, M. (1976). Acta Cryst. B32, 3216-3224.]); Mom & de With (1978[Mom, V. & de With, G. (1978). Acta Cryst. B34, 2785-2789.]); Sinha, 1970[Sinha, U. C. (1970). Acta Cryst. B26, 889-895.]). For other heterocyclic aldehyde azines, see: Lin et al. (2001a[Lin, C.-J., Hwang, W.-S. & Chiang, M. J. (2001a). J. Organomet. Chem. 640, 85-92.],b[Lin, C.-J., Hwang, W.-S. & Chiang, M. J. (2001b). Polyhedron, 20, 3257-3264.]); Wu et al. (2006[Wu, C.-Y., Chen, Y., Jing, S.-Y., Lee, C.-S., Dinda, J. & Hwang, W.-S. (2006). Polyhedron, 25, 3053-3065.]).

[Scheme 1]

Experimental

Crystal data
  • C18H14N4

  • Mr = 286.33

  • Monoclinic, P 21 /c

  • a = 5.0849 (2) Å

  • b = 10.6708 (4) Å

  • c = 13.4435 (5) Å

  • β = 94.366 (3)°

  • V = 727.33 (5) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.08 mm−1

  • T = 295 (2) K

  • 0.33 × 0.27 × 0.17 mm

Data collection
  • Bruker APEX2 diffractometer

  • Absorption correction: none

  • 5388 measured reflections

  • 1659 independent reflections

  • 1085 reflections with I > 2σ(I)

  • Rint = 0.038

Refinement
  • R[F2 > 2σ(F2)] = 0.042

  • wR(F2) = 0.121

  • S = 1.01

  • 1659 reflections

  • 105 parameters

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.17 e Å−3

  • Δρmin = −0.16 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H1⋯N2i 0.87 (2) 2.21 (2) 3.065 (2) 167 (2)
Symmetry code: (i) [-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}].

Data collection: APEX2 (Bruker, 2007[Bruker (2007). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2007[Bruker (2007). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: X-SEED (Barbour, 2001[Barbour, L. J. (2001). J. Supramol. Chem. 1, 189-191.]); software used to prepare material for publication: publCIF (Westrip, 2008[Westrip, S. P. (2008). publCIF. In preparation.]).

Supporting information


Comment top

Azines are readily synthesized by condensing hydrazine with an aldehyde; the crystal structures of a large number of substituted benzaldehdye azines have been reported. The structure of the parent aromatic compound, benzalazine, has been known for a long time (Burke-Laing & Laing, 1976; Mom & de With, 1978; Sinha, 1970). There are few examples of heterocyclic azines, and their rarity can be attributed to the difficulty of synthesizing the starting aldehyde reactant. Among the few are, for example, unsubstituted and methyl-subsituted thiophene-2-aldehyde azine (Lin et al., 2001a, 2001b) and a pyrrole derivative has recently been reported (Wu et al., 2006).

3-Indole azine has been known for some time; it was first synthesized from indole-3-carboxaldehyde and hydrazine in order to examine its psychopharmacological activity (Alemany et al., 1970; Swaminathan Narasimhan, 1964). The title compound was the unexpected decomposition product of the Schiff base derived from the condensation of carbohydrazide and indole-3-carboxaldehyde. The molecule (Scheme I, Fig. 1) lies about a center-of-inversion such that there is half a molecule in the asymmetric unit. The N–N single-bond adopts a trans configuration and the indolyl fused-ring is nearly coplanar with the –CH=N–N=CH– fragment. Adjacent molecules are linked by an N–Hindole···Nazine hydrogen bonds into layer motif (Fig. 2).

Related literature top

For the synthesis, see: Alemany et al. (1970); Swaminathan & Narasimhan (1964). For the crystal structures of some aromatic azines, for example, benzalazine, see: Burke-Laing & Laing (1976); Mom & de With (1978); Sinha, 1970). For other heterocyclic aldehyde azines, see: Lin et al. (2001a,b); Wu et al. (2006).

Experimental top

The reaction of carbohydrazide (0.3 g, 3.3 mmol) and indole -3-carboxaldehyde (1 g, 6.6 mmol) in ethanol under reflux for 2 h gave the corresponding Schiff base. This compound (0.2 g, 0.6 mmol), zinc acetate (0.06 g,0.3 mmol) and several drops of triethylamine were dissolved in 10 ml e thanol. The contents were heated in a 25-ml, stainless-steel Paar bomb for for 2 d at 373 K. The bomb was cooled to room temperature over several hours. Well formed crystals were isolated from the cooled bomb.

Refinement top

Carbon-bound H-atoms were placed in calculated positions (C—H 0.93 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U(C). The amino H-atom was located in a difference Fourier map, and was freely refined.

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2008).

Figures top
[Figure 1] Fig. 1. Displacement ellipsoid plot of (I) at the 50% probability level. H atoms are drawn as spheres of arbitrary radiius.
[Figure 2] Fig. 2. Layer structure of (I).
1H-Indole-3-carbaldehyde azine top
Crystal data top
C18H14N4F(000) = 300
Mr = 286.33Dx = 1.307 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 1012 reflections
a = 5.0849 (2) Åθ = 2.3–23.6°
b = 10.6708 (4) ŵ = 0.08 mm1
c = 13.4435 (5) ÅT = 295 K
β = 94.366 (3)°Irregular block, green–yellow
V = 727.33 (5) Å30.33 × 0.27 × 0.17 mm
Z = 2
Data collection top
Bruker APEX2
diffractometer
1085 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.038
Graphite monochromatorθmax = 27.5°, θmin = 2.4°
ϕ and ω scansh = 66
5388 measured reflectionsk = 913
1659 independent reflectionsl = 1717
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.042H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.121 w = 1/[σ2(Fo2) + (0.0645P)2 + ]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max = 0.001
1659 reflectionsΔρmax = 0.17 e Å3
105 parametersΔρmin = 0.16 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.016 (6)
Crystal data top
C18H14N4V = 727.33 (5) Å3
Mr = 286.33Z = 2
Monoclinic, P21/cMo Kα radiation
a = 5.0849 (2) ŵ = 0.08 mm1
b = 10.6708 (4) ÅT = 295 K
c = 13.4435 (5) Å0.33 × 0.27 × 0.17 mm
β = 94.366 (3)°
Data collection top
Bruker APEX2
diffractometer
1085 reflections with I > 2σ(I)
5388 measured reflectionsRint = 0.038
1659 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0420 restraints
wR(F2) = 0.121H atoms treated by a mixture of independent and constrained refinement
S = 1.01Δρmax = 0.17 e Å3
1659 reflectionsΔρmin = 0.16 e Å3
105 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.4730 (3)0.8059 (1)0.1978 (1)0.0484 (4)
N20.4464 (2)0.5165 (1)0.4519 (1)0.0422 (4)
C10.2718 (3)0.7222 (1)0.1726 (1)0.0425 (4)
C20.1064 (3)0.7130 (2)0.0860 (1)0.0538 (5)
C30.0787 (3)0.6201 (2)0.0817 (1)0.0579 (5)
C40.1034 (4)0.5384 (2)0.1612 (1)0.0546 (4)
C50.0606 (3)0.5473 (1)0.2473 (1)0.0454 (4)
C60.2548 (3)0.6396 (1)0.2540 (1)0.0388 (4)
C70.4578 (3)0.6773 (1)0.3285 (1)0.0400 (4)
C80.5819 (3)0.7783 (1)0.2901 (1)0.0466 (4)
C90.5376 (3)0.6213 (1)0.4228 (1)0.0411 (4)
H10.524 (3)0.865 (2)0.159 (1)0.062 (5)*
H20.12100.76800.03300.065*
H30.19110.61110.02430.070*
H40.23290.47670.15610.065*
H50.04190.49260.30020.054*
H80.72150.82170.32280.056*
H90.66190.66290.46500.049*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.061 (1)0.041 (1)0.043 (1)0.002 (1)0.005 (1)0.012 (1)
N20.063 (1)0.036 (1)0.027 (1)0.001 (1)0.003 (1)0.001 (1)
C10.049 (1)0.039 (1)0.039 (1)0.006 (1)0.006 (1)0.005 (1)
C20.062 (1)0.058 (1)0.040 (1)0.007 (1)0.001 (1)0.014 (1)
C30.060 (1)0.065 (1)0.047 (1)0.005 (1)0.008 (1)0.003 (1)
C40.054 (1)0.050 (1)0.059 (1)0.003 (1)0.001 (1)0.000 (1)
C50.052 (1)0.040 (1)0.045 (1)0.003 (1)0.006 (1)0.004 (1)
C60.046 (1)0.035 (1)0.036 (1)0.007 (1)0.007 (1)0.003 (1)
C70.052 (1)0.034 (1)0.034 (1)0.004 (1)0.004 (1)0.001 (1)
C80.059 (1)0.040 (1)0.041 (1)0.002 (1)0.001 (1)0.003 (1)
C90.056 (1)0.036 (1)0.032 (1)0.003 (1)0.001 (1)0.003 (1)
Geometric parameters (Å, º) top
N1—C81.351 (2)C6—C71.440 (2)
N1—C11.381 (2)C7—C81.370 (2)
N2—C91.283 (2)C7—C91.432 (2)
N2—N2i1.409 (2)N1—H10.87 (2)
C1—C21.387 (2)C2—H20.9300
C1—C61.412 (2)C3—H30.9300
C2—C31.365 (2)C4—H40.9300
C3—C41.393 (2)C5—H50.9300
C4—C51.377 (2)C8—H80.9300
C5—C61.393 (2)C9—H90.9300
C8—N1—C1109.2 (1)N2—C9—C7123.4 (1)
C9—N2—N2i112.0 (1)C8—N1—H1126 (1)
N1—C1—C2129.9 (1)C1—N1—H1125 (1)
N1—C1—C6107.6 (1)C3—C2—H2121.4
C2—C1—C6122.5 (2)C1—C2—H2121.4
C3—C2—C1117.3 (2)C2—C3—H3119.2
C2—C3—C4121.7 (2)C4—C3—H3119.2
C5—C4—C3121.2 (2)C5—C4—H4119.4
C4—C5—C6118.9 (1)C3—C4—H4119.4
C5—C6—C1118.5 (1)C4—C5—H5120.5
C5—C6—C7135.2 (1)C6—C5—H5120.5
C1—C6—C7106.3 (1)N1—C8—H8124.8
C8—C7—C9123.7 (1)C7—C8—H8124.8
C8—C7—C6106.5 (1)N2—C9—H9118.3
C9—C7—C6129.7 (1)C7—C9—H9118.3
N1—C8—C7110.5 (1)
C8—N1—C1—C2179.5 (2)C2—C1—C6—C7179.4 (1)
C8—N1—C1—C60.5 (2)C5—C6—C7—C8178.6 (2)
N1—C1—C2—C3179.6 (2)C1—C6—C7—C80.5 (2)
C6—C1—C2—C30.4 (2)C5—C6—C7—C95.1 (3)
C1—C2—C3—C40.7 (3)C1—C6—C7—C9175.9 (2)
C2—C3—C4—C50.7 (3)C1—N1—C8—C70.2 (2)
C3—C4—C5—C60.3 (2)C9—C7—C8—N1176.5 (1)
C4—C5—C6—C11.3 (2)C6—C7—C8—N10.2 (2)
C4—C5—C6—C7179.7 (2)N2i—N2—C9—C7178.9 (1)
N1—C1—C6—C5178.6 (1)C8—C7—C9—N2169.5 (1)
C2—C1—C6—C51.4 (2)C6—C7—C9—N26.3 (3)
N1—C1—C6—C70.6 (2)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···N2ii0.87 (2)2.21 (2)3.065 (2)167 (2)
Symmetry code: (ii) x+1, y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC18H14N4
Mr286.33
Crystal system, space groupMonoclinic, P21/c
Temperature (K)295
a, b, c (Å)5.0849 (2), 10.6708 (4), 13.4435 (5)
β (°) 94.366 (3)
V3)727.33 (5)
Z2
Radiation typeMo Kα
µ (mm1)0.08
Crystal size (mm)0.33 × 0.27 × 0.17
Data collection
DiffractometerBruker APEX2
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
5388, 1659, 1085
Rint0.038
(sin θ/λ)max1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.121, 1.01
No. of reflections1659
No. of parameters105
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.17, 0.16

Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001), publCIF (Westrip, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···N2i0.87 (2)2.21 (2)3.065 (2)167 (2)
Symmetry code: (i) x+1, y+1/2, z+1/2.
 

Acknowledgements

We thank the Science Fund (12–02-03–2031) for supporting this study, and the University of Malaya for the purchase of the diffractometer.

References

First citationAlemany, A., Bernabe, M., Fernandez Alvarez, E., Lora-Tamayo, M. & Nieto Lopez, O. (1970). Anal. Quim. 66, 681–688.  CAS Google Scholar
First citationBarbour, L. J. (2001). J. Supramol. Chem. 1, 189–191.  CrossRef CAS Google Scholar
First citationBruker (2007). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationBurke-Laing, M. & Laing, M. (1976). Acta Cryst. B32, 3216–3224.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
First citationLin, C.-J., Hwang, W.-S. & Chiang, M. J. (2001a). J. Organomet. Chem. 640, 85–92.  Web of Science CSD CrossRef CAS Google Scholar
First citationLin, C.-J., Hwang, W.-S. & Chiang, M. J. (2001b). Polyhedron, 20, 3257–3264.  Google Scholar
First citationMom, V. & de With, G. (1978). Acta Cryst. B34, 2785–2789.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSinha, U. C. (1970). Acta Cryst. B26, 889–895.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
First citationSwaminathan, S. & Narasimhan, K. (1964). Indian J. Chem. 2, 423–424.  CAS Google Scholar
First citationWestrip, S. P. (2008). publCIF. In preparation.  Google Scholar
First citationWu, C.-Y., Chen, Y., Jing, S.-Y., Lee, C.-S., Dinda, J. & Hwang, W.-S. (2006). Polyhedron, 25, 3053–3065.  Web of Science CSD CrossRef CAS Google Scholar

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