1H-Indole-3-carbaldehyde azine

Rizal, M.R.; Ali, H.M.; Ng, S.W.

doi:10.1107/S1600536808003164

organic compounds

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ISSN: 2056-9890

Volume 64| Part 3| March 2008| Page o555

doi:10.1107/S1600536808003164

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1H-Indole-3-carbaldehyde azine

Mohd. Razali Rizal,^a Hapipah M. Ali ^a and Seik Weng Ng ^a ^*

^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 ); 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

Crystal data

C₁₈H₁₄N₄
M_r = 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)
R_int = 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
Δρ_max = 0.17 e Å⁻³
Δρ_min = −0.16 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

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 code: (i) $[-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Data collection: APEX2 (Bruker, 2007 ); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; 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 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808003164/fl2186sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808003164/fl2186Isup2.hkl

checkCIF report

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–H_indole···N_azine 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.

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

	Fig. 1. Displacement ellipsoid plot of (I) at the 50% probability level. H atoms are drawn as spheres of arbitrary radiius.
	Fig. 2. Layer structure of (I).

1H-Indole-3-carbaldehyde azine top

Crystal data top

C₁₈H₁₄N₄	F(000) = 300
M_r = 286.33	D_x = 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 = 2.3–23.6°
b = 10.6708 (4) Å	µ = 0.08 mm⁻¹
c = 13.4435 (5) Å	T = 295 K
β = 94.366 (3)°	Irregular block, green–yellow
V = 727.33 (5) Å³	0.33 × 0.27 × 0.17 mm
Z = 2

Data collection top

Bruker APEX2 diffractometer	1085 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.038
Graphite monochromator	θ_max = 27.5°, θ_min = 2.4°
ϕ and ω scans	h = −6→6
5388 measured reflections	k = −9→13
1659 independent reflections	l = −17→17

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.042	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.121	w = 1/[σ²(F_o²) + (0.0645P)² + ] where P = (F_o² + 2F_c²)/3
S = 1.01	(Δ/σ)_max = 0.001
1659 reflections	Δρ_max = 0.17 e Å⁻³
105 parameters	Δρ_min = −0.16 e Å⁻³
0 restraints	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)

Crystal data top

C₁₈H₁₄N₄	V = 727.33 (5) Å³
M_r = 286.33	Z = 2
Monoclinic, P2₁/c	Mo Kα radiation
a = 5.0849 (2) Å	µ = 0.08 mm⁻¹
b = 10.6708 (4) Å	T = 295 K
c = 13.4435 (5) Å	0.33 × 0.27 × 0.17 mm
β = 94.366 (3)°

Data collection top

Bruker APEX2 diffractometer	1085 reflections with I > 2σ(I)
5388 measured reflections	R_int = 0.038
1659 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.042	0 restraints
wR(F²) = 0.121	H atoms treated by a mixture of independent and constrained refinement
S = 1.01	Δρ_max = 0.17 e Å⁻³
1659 reflections	Δρ_min = −0.16 e Å⁻³
105 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
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*

Atomic displacement parameters (Å²) top

	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)

Geometric parameters (Å, º) top

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 code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

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 code: (ii) −x+1, y+1/2, −z+1/2.

Experimental details

Crystal data
Chemical formula	C₁₈H₁₄N₄
M_r	286.33
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	295
a, b, c (Å)	5.0849 (2), 10.6708 (4), 13.4435 (5)
β (°)	94.366 (3)
V (Å³)	727.33 (5)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.08
Crystal size (mm)	0.33 × 0.27 × 0.17

Data collection
Diffractometer	Bruker APEX2 diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	5388, 1659, 1085
R_int	0.038
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.042, 0.121, 1.01
No. of reflections	1659
No. of parameters	105
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	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···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 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

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