Acta Cryst. (2008). E64, o555 [ doi:10.1107/S1600536808003164 ]
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.
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.
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.
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).
![[Figure 1]](./fl2186fig1thm.gif)
| Fig. 1. Displacement ellipsoid plot of (I) at the 50% probability level. H atoms are drawn as spheres of arbitrary radiius. |
![[Figure 2]](./fl2186fig2thm.gif)
| Fig. 2. Layer structure of (I). |
| C18H14N4 | F000 = 300 |
| Mr = 286.33 | Dx = 1.307 Mg m−3 |
| Monoclinic, P21/c | Mo Kα radiation λ = 0.71073 Å |
| Hall symbol: -P 2ybc | Cell parameters from 1012 reflections |
| a = 5.0849 (2) Å | θ = 2.3–23.6º |
| b = 10.6708 (4) Å | µ = 0.08 mm−1 |
| c = 13.4435 (5) Å | T = 295 (2) K |
| β = 94.366 (3)º | Irregular block, green–yellow |
| V = 727.33 (5) Å3 | 0.33 × 0.27 × 0.17 mm |
| Z = 2 |
| Bruker APEX2 diffractometer | 1085 reflections with I > 2σ(I) |
| Radiation source: fine-focus sealed tube | Rint = 0.038 |
| Monochromator: graphite | θmax = 27.5º |
| T = 295(2) K | θmin = 2.4º |
| φ and ω scans | h = −6→6 |
| Absorption correction: none | k = −9→13 |
| 5388 measured reflections | l = −17→17 |
| 1659 independent reflections |
| Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
| Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
| R[F2 > 2σ(F2)] = 0.042 | w = 1/[σ2(Fo2) + (0.0645P)2 + ] where P = (Fo2 + 2Fc2)/3 |
| wR(F2) = 0.121 | (Δ/σ)max = 0.001 |
| S = 1.01 | Δρmax = 0.17 e Å−3 |
| 1659 reflections | Δρmin = −0.16 e Å−3 |
| 105 parameters | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.016 (6) |
| Secondary atom site location: difference Fourier map |
| C18H14N4 | V = 727.33 (5) Å3 |
| Mr = 286.33 | Z = 2 |
| Monoclinic, P21/c | Mo Kα |
| a = 5.0849 (2) Å | µ = 0.08 mm−1 |
| b = 10.6708 (4) Å | T = 295 (2) K |
| c = 13.4435 (5) Å | 0.33 × 0.27 × 0.17 mm |
| β = 94.366 (3)º |
| Bruker APEX2 diffractometer | 1659 independent reflections |
| Absorption correction: none | 1085 reflections with I > 2σ(I) |
| 5388 measured reflections | Rint = 0.038 |
| R[F2 > 2σ(F2)] = 0.042 | 105 parameters |
| wR(F2) = 0.121 | H atoms treated by a mixture of independent and constrained refinement |
| S = 1.01 | Δρmax = 0.17 e Å−3 |
| 1659 reflections | Δρmin = −0.16 e Å−3 |
| x | y | z | Uiso*/Ueq | ||
| N1 | 0.4730 (3) | 0.8059 (1) | 0.1978 (1) | 0.0484 (4) | |
| N2 | 0.4464 (2) | 0.5165 (1) | 0.4519 (1) | 0.0422 (4) | |
| C1 | 0.2718 (3) | 0.7222 (1) | 0.1726 (1) | 0.0425 (4) | |
| C2 | 0.1064 (3) | 0.7130 (2) | 0.0860 (1) | 0.0538 (5) | |
| C3 | −0.0787 (3) | 0.6201 (2) | 0.0817 (1) | 0.0579 (5) | |
| C4 | −0.1034 (4) | 0.5384 (2) | 0.1612 (1) | 0.0546 (4) | |
| C5 | 0.0606 (3) | 0.5473 (1) | 0.2473 (1) | 0.0454 (4) | |
| C6 | 0.2548 (3) | 0.6396 (1) | 0.2540 (1) | 0.0388 (4) | |
| C7 | 0.4578 (3) | 0.6773 (1) | 0.3285 (1) | 0.0400 (4) | |
| C8 | 0.5819 (3) | 0.7783 (1) | 0.2901 (1) | 0.0466 (4) | |
| C9 | 0.5376 (3) | 0.6213 (1) | 0.4228 (1) | 0.0411 (4) | |
| H1 | 0.524 (3) | 0.865 (2) | 0.159 (1) | 0.062 (5)* | |
| H2 | 0.1210 | 0.7680 | 0.0330 | 0.065* | |
| H3 | −0.1911 | 0.6111 | 0.0243 | 0.070* | |
| H4 | −0.2329 | 0.4767 | 0.1561 | 0.065* | |
| H5 | 0.0419 | 0.4926 | 0.3002 | 0.054* | |
| H8 | 0.7215 | 0.8217 | 0.3228 | 0.056* | |
| H9 | 0.6619 | 0.6629 | 0.4650 | 0.049* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| N1 | 0.061 (1) | 0.041 (1) | 0.043 (1) | −0.002 (1) | 0.005 (1) | 0.012 (1) |
| N2 | 0.063 (1) | 0.036 (1) | 0.027 (1) | −0.001 (1) | −0.003 (1) | 0.001 (1) |
| C1 | 0.049 (1) | 0.039 (1) | 0.039 (1) | 0.006 (1) | 0.006 (1) | 0.005 (1) |
| C2 | 0.062 (1) | 0.058 (1) | 0.040 (1) | 0.007 (1) | −0.001 (1) | 0.014 (1) |
| C3 | 0.060 (1) | 0.065 (1) | 0.047 (1) | 0.005 (1) | −0.008 (1) | 0.003 (1) |
| C4 | 0.054 (1) | 0.050 (1) | 0.059 (1) | −0.003 (1) | −0.001 (1) | 0.000 (1) |
| C5 | 0.052 (1) | 0.040 (1) | 0.045 (1) | 0.003 (1) | 0.006 (1) | 0.004 (1) |
| C6 | 0.046 (1) | 0.035 (1) | 0.036 (1) | 0.007 (1) | 0.007 (1) | 0.003 (1) |
| C7 | 0.052 (1) | 0.034 (1) | 0.034 (1) | 0.004 (1) | 0.004 (1) | 0.001 (1) |
| C8 | 0.059 (1) | 0.040 (1) | 0.041 (1) | −0.002 (1) | 0.001 (1) | 0.003 (1) |
| C9 | 0.056 (1) | 0.036 (1) | 0.032 (1) | −0.003 (1) | −0.001 (1) | −0.003 (1) |
| N1—C8 | 1.351 (2) | C6—C7 | 1.440 (2) |
| N1—C1 | 1.381 (2) | C7—C8 | 1.370 (2) |
| N2—C9 | 1.283 (2) | C7—C9 | 1.432 (2) |
| N2—N2i | 1.409 (2) | N1—H1 | 0.87 (2) |
| C1—C2 | 1.387 (2) | C2—H2 | 0.9300 |
| C1—C6 | 1.412 (2) | C3—H3 | 0.9300 |
| C2—C3 | 1.365 (2) | C4—H4 | 0.9300 |
| C3—C4 | 1.393 (2) | C5—H5 | 0.9300 |
| C4—C5 | 1.377 (2) | C8—H8 | 0.9300 |
| C5—C6 | 1.393 (2) | C9—H9 | 0.9300 |
| C8—N1—C1 | 109.2 (1) | N2—C9—C7 | 123.4 (1) |
| C9—N2—N2i | 112.0 (1) | C8—N1—H1 | 126 (1) |
| N1—C1—C2 | 129.9 (1) | C1—N1—H1 | 125 (1) |
| N1—C1—C6 | 107.6 (1) | C3—C2—H2 | 121.4 |
| C2—C1—C6 | 122.5 (2) | C1—C2—H2 | 121.4 |
| C3—C2—C1 | 117.3 (2) | C2—C3—H3 | 119.2 |
| C2—C3—C4 | 121.7 (2) | C4—C3—H3 | 119.2 |
| C5—C4—C3 | 121.2 (2) | C5—C4—H4 | 119.4 |
| C4—C5—C6 | 118.9 (1) | C3—C4—H4 | 119.4 |
| C5—C6—C1 | 118.5 (1) | C4—C5—H5 | 120.5 |
| C5—C6—C7 | 135.2 (1) | C6—C5—H5 | 120.5 |
| C1—C6—C7 | 106.3 (1) | N1—C8—H8 | 124.8 |
| C8—C7—C9 | 123.7 (1) | C7—C8—H8 | 124.8 |
| C8—C7—C6 | 106.5 (1) | N2—C9—H9 | 118.3 |
| C9—C7—C6 | 129.7 (1) | C7—C9—H9 | 118.3 |
| N1—C8—C7 | 110.5 (1) | ||
| C8—N1—C1—C2 | −179.5 (2) | C2—C1—C6—C7 | 179.4 (1) |
| C8—N1—C1—C6 | 0.5 (2) | C5—C6—C7—C8 | −178.6 (2) |
| N1—C1—C2—C3 | −179.6 (2) | C1—C6—C7—C8 | 0.5 (2) |
| C6—C1—C2—C3 | 0.4 (2) | C5—C6—C7—C9 | 5.1 (3) |
| C1—C2—C3—C4 | 0.7 (3) | C1—C6—C7—C9 | −175.9 (2) |
| C2—C3—C4—C5 | −0.7 (3) | C1—N1—C8—C7 | −0.2 (2) |
| C3—C4—C5—C6 | −0.3 (2) | C9—C7—C8—N1 | 176.5 (1) |
| C4—C5—C6—C1 | 1.3 (2) | C6—C7—C8—N1 | −0.2 (2) |
| C4—C5—C6—C7 | −179.7 (2) | N2i—N2—C9—C7 | −178.9 (1) |
| N1—C1—C6—C5 | 178.6 (1) | C8—C7—C9—N2 | −169.5 (1) |
| C2—C1—C6—C5 | −1.4 (2) | C6—C7—C9—N2 | 6.3 (3) |
| N1—C1—C6—C7 | −0.6 (2) |
| Symmetry codes: (i) −x+1, −y+1, −z+1. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H1···N2ii | 0.87 (2) | 2.21 (2) | 3.065 (2) | 167 (2) |
| Symmetry codes: (ii) −x+1, y+1/2, −z+1/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H1···N2i | 0.87 (2) | 2.21 (2) | 3.065 (2) | 167 (2) |
| Symmetry codes: (i) −x+1, y+1/2, −z+1/2. |
We thank the Science Fund (12–02–03–2031) for supporting this study, and the University of Malaya for the purchase of the diffractometer.
Alemany, A., Bernabe, M., Fernandez Alvarez, E., Lora-Tamayo, M. & Nieto Lopez, O. (1970). Anal. Quim. 66, 681–688.
Barbour, L. J. (2001). J. Supramol. Chem. 1, 189–191.
Bruker (2007). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.
Burke-Laing, M. & Laing, M. (1976). Acta Cryst. B32, 3216–3224.
Lin, C.-J., Hwang, W.-S. & Chiang, M. J. (2001a). J. Organomet. Chem. 640, 85–92.
Lin, C.-J., Hwang, W.-S. & Chiang, M. J. (2001b). Polyhedron, 20, 3257–3264.
Mom, V. & de With, G. (1978). Acta Cryst. B34, 2785–2789.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.
Sinha, U. C. (1970). Acta Cryst. B26, 889–895.
Swaminathan, S. & Narasimhan, K. (1964). Indian J. Chem. 2, 423–424.
Westrip, S. P. (2008). publCIF. In preparation.
Wu, C.-Y., Chen, Y., Jing, S.-Y., Lee, C.-S., Dinda, J. & Hwang, W.-S. (2006). Polyhedron, 25, 3053–3065.
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).