Octane-1,8-diyl­bis­[3-ethyl-1H-1,2,4-triazol-5(4H)-one]

The title compound, C₁₆H₂₈N₆O₂, has a centre of symmetry. There are two planar 1,2,4-triazole rings, connected by an octane group. The crystal structure is stabilized by C—H...N, C—H...O and N—H...O intermolecular hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.046
• wR factor = 0.136
• Data-to-parameter ratio = 16.5

checkCIF/PLATON results

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S1. Comment

Schiff bases of 4-amino-1,2,4-triazole have received considerable attention over the past few decades (Kitaev et al., 1971; Mazza et al., 1976; Kargin et al., 1988). It is of interest that some of them are anti-inflammatory agents (Gupta & Bhargava, 1978) and new concidiostatic drugs (Colauti et al., 1971). Some other diverse pharmacological properties of 1,2,4-triazoles are analgesic, antiasthmatic, diuretic, fungicidal, bactericidal and pesticidal activities (Bennur et al., 1976; Webb & Parsons, 1977; Heubach et al., 1980; Mohammed et al., 1993). Therefore, the structures of 1,2,4-triazole derivatives with different substituents have been the subject of much interest in our laboratory. Examples include 1-acetyl-3-(p-chlorobenzyl)-4-benzylidenamino-4,5-dihydro-1H- 1,2,4-triazol-5-one, (II) (Çoruh, 2002), 1-acetyl-4-(p-chlorobenzylidenamino)-3-acetyl-4,5-dihydro-1H- 1,2,4-triazol-5-one, (III) (Çoruh, Kahveci, Şaşmaz, A~gar & Kim, 2003), 1-acetyl-3-(p-chlorobenzyl)-4-(p-chlorobenzylidenamino)-4,5-dihydro-1H- 1,2,4-triazol-5-one, (IV) (Ocak et al., 2003), and C—H···O and C—H···π interactions in 1-acetyl-4-(p-chlorobenzylidenamino)-3-ethyl-4,5-dihydro-1H-1,2,4-triazol-5-one, (V) (Çoruh, Kahveci, Şaşmaz, A~gar, Kim & Erdönmez, 2003).

The molecular structure of (I) is shown in Fig.1. The compound consists of two 1,2,4-triazole rings, each with an ethyl group on the C atom in the 3-position and an oxo O atom on the C atom at the 5-position, and linked by an octane chain attached to their N atoms at the 4-position. The molecule has a centre of symmetry in the middle of this connecting chain.

In the molecule, the placement of the ethyl group and the oxo O atom are very similar to a previously reported example (Çoruh, Kahveci, Şaşmaz, A~gar & Kim, 2003). Because of a C—H···N hydrogen bond involving N1 as acceptor (Table 2), the N3═C1 bond length, 1.288 (3) Å, is a little longer than some values reported in the literature [1.272 (3) Å in C₁₃H₁₃ClN₄O₂ (,Coruh, Kahveci, Şaşmaz, A~gar, Kim & Erdönmez, 2003), 1.261 (4) Å in the 4-amino-3-methyl-1,2,4-triazole-5-thione derivative of p-nitrophenylaldehyde (Liu et al., 1999), and 1.267 (2) Å in 4-(4-hydroxybenzylidenamino)-4H-1,2,4-triazole hemihydrate (Zhu et al., 2000)]. However, it is close to other reported values (Puviarasan et al., 1999; Çoruh, Kahveci, Şaşmaz, A~gar & Kim, 2003; Ocak et al., 2003). In the 1,2,4-triazole ring, atoms N1 and N2 have no substitutents, and the N1—N2 bond length, 1.372 (2) Å, is essentially identical to 1.373 (2) Å reported for a similar compound (Liu et al., 1999). This is shorter than in compounds where at least one N atom has a substituent [1.394 (3) Å (Çoruh, Kahveci, Şaşmaz, A~gar, Kim & Erdönmez, 2003), 1.399 (2) Å (Çoruh, Kahveci, Şaşmaz, A~gar & Kim, 2003) and 1.404 (4) Å (Ocak et al., 2003)]. In (I), the 1,2,4-triazole ring is planar, with a maximum deviation from the least-squares plane of 0.0017 (1) Å for atom N1. Atom O1 is also in the plane, with a deviation of only 0.0006 (1) Å.

In addition to van der Waals interactions, the molecular structure and crystal packing of (I) are stabilized by C—H···O, C—H···N and N—H···O intermolecular interactions (Fig. 2 and Table 2).

S2. Experimental

1,8-Diaminooctane (1,44 g, 0.001 mol) was dissolved in water (100 ml) and ethyl propionate ethoxycarbonylhydrazone (3.76 g, 0.02 mol) was added. The reaction mixture was refluxed for 6 h and then cooled to room temperature. The precipitate was filtered off and washed with cold water. After drying in vacuo, the solid product was recrystallized from ethanol-water (1:2) to afford the desired compound, (I) (yield 2.82 g, 84%). M.p. 452–453 K. IR (KBr, cm⁻¹): ν(N—H) 3165, 3063; ν(C═O) 1680 and ν(C═N) 1560. ¹H NMR (p.p.m. in DMSO-d₆): 0.54, 1.86 (m, 18H, 6CH₂, 2CH₃); 2.54 (q, 4H, 2CH₂); 3.44 (t, 2 N-CH₂, 4H); 11.26 (s, 2NH, 2H).

S3. Refinement

The H atoms were positioned geometrically and refined using a riding model, with ethyl C—H = 0.97 Å, methyl C—H = 0.96 Å, and N—H = 0.86 Å; U_iso(H) was set to 1.2U_eq of the parent atom in each case.

Computing details

Data collection: CAD-4-PC Software (Enraf-Nonius, 1992); cell refinement: CAD-4-PC Software; data reduction: XCAD4 (Harms, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 1997); software used to prepare material for publication: SHELXL97 and WinGX (Farrugia, 1999).

Figures

	Fig. 1. A view of (I) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. The strong hydrogen-bond network observed in (I), viwed along the a axis.

(I)

Crystal data

C16H28N6O2	F(000) = 364
Mr = 336.44	Dx = 1.205 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.7852 (10) Å	Cell parameters from 25 reflections
b = 7.829 (2) Å	θ = 8.0–12.8°
c = 17.550 (3) Å	µ = 0.08 mm^−1
β = 95.894 (10)°	T = 293 K
V = 927.4 (3) Å^3	Block, colorless
Z = 2	0.45 × 0.35 × 0.3 mm

Data collection

Enraf-Nonius CAD-4 MACH3 diffractometer	Rint = 0.023
Radiation source: fine-focus sealed tube	θmax = 26.0°, θmin = 2.3°
Graphite monochromator	h = 0→8
2θ/ω scans	k = 0→9
1975 measured reflections	l = −21→21
1817 independent reflections	3 standard reflections every 60 min
1162 reflections with I > 2σ(I)	intensity decay: none

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)] = 0.046	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.136	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0712P)^2 + 0.0879P] where P = (Fo^2 + 2Fc^2)/3
1817 reflections	(Δ/σ)max = 0.001
110 parameters	Δρmax = 0.14 e Å^−3
0 restraints	Δρmin = −0.22 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
O1	0.0289 (2)	0.84498 (19)	0.25180 (9)	0.0811 (5)
C1	0.7656 (4)	1.0832 (4)	0.42183 (19)	0.1061 (10)
H1A	0.7604	1.1679	0.3821	0.127*
H1B	0.9014	1.0572	0.4387	0.127*
H1C	0.7013	1.1261	0.4642	0.127*
C2	0.6635 (3)	0.9264 (3)	0.39173 (15)	0.0829 (7)
H2A	0.6550	0.8469	0.4337	0.100*
H2B	0.7422	0.8731	0.3552	0.100*
C3	0.4614 (3)	0.9583 (2)	0.35393 (11)	0.0538 (5)
N1	0.3803 (2)	1.10689 (19)	0.34601 (10)	0.0630 (5)
N2	0.2013 (2)	1.07601 (19)	0.30454 (10)	0.0605 (5)
H2	0.1164	1.1546	0.2909	0.073*
C4	0.1730 (3)	0.9116 (2)	0.28774 (11)	0.0539 (5)
N3	0.3423 (2)	0.83473 (17)	0.31990 (9)	0.0502 (4)
C5	0.3778 (3)	0.6505 (2)	0.31894 (12)	0.0630 (5)
H5A	0.5136	0.6301	0.3087	0.076*
H5B	0.2916	0.5998	0.2775	0.076*
C6	0.3422 (3)	0.5636 (2)	0.39307 (12)	0.0620 (5)
H6A	0.3715	0.4429	0.3888	0.074*
H6B	0.4338	0.6102	0.4339	0.074*
C7	0.1346 (3)	0.5825 (2)	0.41489 (11)	0.0600 (5)
H7A	0.0421	0.5404	0.3733	0.072*
H7B	0.1070	0.7028	0.4218	0.072*
C8	0.1017 (3)	0.4874 (2)	0.48744 (12)	0.0637 (6)
H8A	0.1225	0.3664	0.4794	0.076*
H8B	0.1994	0.5249	0.5282	0.076*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0786 (10)	0.0590 (9)	0.0969 (11)	−0.0137 (7)	−0.0332 (8)	0.0029 (8)
C1	0.0759 (17)	0.114 (2)	0.119 (2)	−0.0185 (15)	−0.0318 (15)	−0.0050 (18)
C2	0.0605 (13)	0.0756 (15)	0.1065 (19)	−0.0005 (11)	−0.0212 (12)	0.0103 (13)
C3	0.0523 (10)	0.0462 (10)	0.0612 (11)	−0.0002 (8)	−0.0030 (9)	0.0027 (8)
N1	0.0578 (10)	0.0460 (9)	0.0810 (12)	−0.0022 (7)	−0.0138 (8)	−0.0008 (8)
N2	0.0521 (9)	0.0418 (8)	0.0836 (12)	0.0025 (7)	−0.0119 (8)	0.0045 (7)
C4	0.0555 (11)	0.0449 (10)	0.0586 (11)	−0.0040 (8)	−0.0073 (9)	0.0057 (8)
N3	0.0571 (9)	0.0383 (8)	0.0540 (9)	0.0013 (6)	−0.0005 (7)	0.0014 (6)
C5	0.0772 (13)	0.0420 (10)	0.0693 (13)	0.0083 (10)	0.0048 (10)	−0.0038 (9)
C6	0.0715 (13)	0.0399 (10)	0.0727 (13)	0.0058 (9)	−0.0014 (10)	0.0072 (9)
C7	0.0674 (13)	0.0481 (11)	0.0613 (12)	−0.0014 (9)	−0.0094 (9)	0.0085 (9)
C8	0.0662 (11)	0.0515 (11)	0.0700 (13)	−0.0027 (9)	−0.0096 (10)	0.0128 (10)

Geometric parameters (Å, º)

O1—C4	1.224 (2)	N3—C5	1.463 (2)
C1—C2	1.480 (3)	C5—C6	1.509 (3)
C1—H1A	0.960	C5—H5A	0.970
C1—H1B	0.960	C5—H5B	0.970
C1—H1C	0.960	C6—C7	1.505 (3)
C2—C3	1.482 (3)	C6—H6A	0.970
C2—H2A	0.970	C6—H6B	0.970
C2—H2B	0.970	C7—C8	1.512 (3)
C3—N1	1.288 (2)	C7—H7A	0.970
C3—N3	1.359 (2)	C7—H7B	0.970
N1—N2	1.372 (2)	C8—C8^i	1.504 (4)
N2—C4	1.330 (2)	C8—H8A	0.970
N2—H2	0.860	C8—H8B	0.970
C4—N3	1.367 (2)
C2—C1—H1A	109.5	N3—C5—C6	113.17 (17)
C2—C1—H1B	109.5	N3—C5—H5A	108.9
H1A—C1—H1B	109.5	C6—C5—H5A	108.9
C2—C1—H1C	109.5	N3—C5—H5B	108.9
H1A—C1—H1C	109.5	C6—C5—H5B	108.9
H1B—C1—H1C	109.5	H5A—C5—H5B	107.8
C1—C2—C3	113.4 (2)	C7—C6—C5	114.30 (16)
C1—C2—H2A	108.9	C7—C6—H6A	108.7
C3—C2—H2A	108.9	C5—C6—H6A	108.7
C1—C2—H2B	108.9	C7—C6—H6B	108.7
C3—C2—H2B	108.9	C5—C6—H6B	108.7
H2A—C2—H2B	107.7	H6A—C6—H6B	107.6
N1—C3—N3	111.56 (15)	C6—C7—C8	112.91 (15)
N1—C3—C2	124.48 (17)	C6—C7—H7A	109.0
N3—C3—C2	123.88 (17)	C8—C7—H7A	109.0
C3—N1—N2	104.08 (14)	C6—C7—H7B	109.0
C4—N2—N1	112.83 (14)	C8—C7—H7B	109.0
C4—N2—H2	123.6	H7A—C7—H7B	107.8
N1—N2—H2	123.6	C8^i—C8—C7	113.70 (19)
O1—C4—N2	128.01 (18)	C8^i—C8—H8A	108.8
O1—C4—N3	128.20 (18)	C7—C8—H8A	108.8
N2—C4—N3	103.79 (15)	C8^i—C8—H8B	108.8
C3—N3—C4	107.73 (14)	C7—C8—H8B	108.8
C3—N3—C5	128.06 (16)	H8A—C8—H8B	107.7
C4—N3—C5	124.16 (16)
C1—C2—C3—N1	1.2 (4)	C2—C3—N3—C5	5.7 (3)
C1—C2—C3—N3	177.8 (2)	O1—C4—N3—C3	179.9 (2)
N3—C3—N1—N2	−0.3 (2)	N2—C4—N3—C3	0.0 (2)
C2—C3—N1—N2	176.6 (2)	O1—C4—N3—C5	−2.4 (3)
C3—N1—N2—C4	0.3 (2)	N2—C4—N3—C5	177.65 (17)
N1—N2—C4—O1	179.9 (2)	C3—N3—C5—C6	77.2 (3)
N1—N2—C4—N3	−0.2 (2)	C4—N3—C5—C6	−100.0 (2)
N1—C3—N3—C4	0.2 (2)	N3—C5—C6—C7	59.8 (2)
C2—C3—N3—C4	−176.7 (2)	C5—C6—C7—C8	177.38 (17)
N1—C3—N3—C5	−177.33 (18)	C6—C7—C8—C8^i	176.8 (2)

Symmetry code: (i) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O1^ii	0.86	1.90	2.745 (3)	168
C2—H2B···O1^iii	0.97	2.80	3.719 (3)	158
C5—H5A···N2^iv	0.97	2.94	3.803 (3)	148
C7—H7A···O1^v	0.97	2.68	3.547 (3)	149
C6—H6A···N1^vi	0.97	2.74	3.685 (3)	165

Symmetry codes: (ii) −x, y+1/2, −z+1/2; (iii) x+1, y, z; (iv) −x+1, y−1/2, −z+1/2; (v) −x, y−1/2, −z+1/2; (vi) x, y−1, z.