C—H...O and C—H...π interactions in 1-acetyl-4-(p-chloro­benzyl­idene­amino)-3-ethyl-4,5-di­hydro-1H-1,2,4-triazol-5-one

The title compound, C₁₃H₁₃ClN₄O₂, contains both a phenyl and a triazole ring, both of which are approximately coplanar with the entire mol­ecule. The triazole ring has substituents at the 1-, 2- and 4-positions. Intramolecular C—H...O and C—H...N interactions, together with intermolecular C—H...O and C—H...π interactions, help to stabilize the structure.

S1. Comment

1,2,4-Triazole ring systems are typical planar six-π-electron partially aromatic systems that possess an extensive chemistry (Temple, 1981; Benson, 1967). 1,2,4-Triazole and its derivatives are starting materials for the synthesis of many heterocycles (Desenko, 1995). In addition to its extensive chemical significance, the 1,2,4-triazole nucleus is also associated with diverse pharmacological properties, such as analgesic, anti-asthmatic, diuretic, anti-inflammantory, fungicidal, bactericidal and pesticidal activities (Bennur et al., 1976; Webb et al., 1977; Heubach et al., 1980; Mohamed et al., 1993). Knowledge of the molecular structure of these compounds is important in understanding their reactivity under condensation reaction conditions. Therefore, the crystal structure of the title compound, (I), has been investigated.

Compound (I) (Fig. 1) consists of a triazole ring with an acetyl group substituted at the N atom in the 1-position, a methyl group substituted at the C atom in the 3-position, an O atom substituted at the C atom at the 5-position and a 4-(para-chlorobenzylidenamino)-4,5-dihydro-1H group substituted at the 4-position. The N═C bond lengths [N1═C7, 1.272 (3) and N3═C9, 1.278 (3) Å] agree with literature values (Liu et al., 1999; Puviarasan et al., 1999), the corresponding values reported in the literature being 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).

The presence of an acetyl group on atom N4 causes a lengthening of the N—N bond length [N3—N4 = 1.394 (3) Å] with respect to the corresponding bonds in 5-(2-chlorophenyl)-4-phenyl-3,4-dihydro-2H- 1,2,4-triazole-3-thione (N—N = 1.374 (2) Å; Puviarasan et al., 1999) and in 4-methyl-1,2,4-triazole and 1-methyl-tetrazole (N—N = 1.344 (2) Å; Palmer et al., 1996).? The Cl—C3 bond length [1.737 (3) Å] agrees with those found in 3,5-bis(2-pyridyl)-4-p-chlorophenyl- 4H-1,2,4-triazole (Wang et al., 1998) and C₁₄H₁₀ClN₃S (Puviarasan et al., 1999). Atom N4, carrying the acetyl substituent, is trigonal?, the sum of the three bond angles around it being 359.96°. Atom N2, carrying the 4-(p-chlorobenzylidenamino)-4,5-dihydro-1H substituent, is also trigonal, the sum of the three bond angles around it being 360°.

In (I), the 1,2,4-triazol ring (A; C8/N2/C9/N3/N4) and the phenyl ring (B; C1–C6) are planar, with the maximum deviation from the least-squares planes being 0.003 (2) Å for atom C8 and 0.004 (3) Å for atom C3, respectively. The dihedral angle between the planes of rings A and B is 6.13°, indicating that the whole molecule is nearly planar, which correlates well with the value observed in 1-acetyl-4-(p-chlorobenzyelidenamino)-3-methyl-4,5-dihydro- 1H-1,2,4-triazol-5-one (Çoruh et al., 2003).

There are intramolecular and intermolecular C—H···O interactions and intramolecular C—H···N interactions in the structure of (I). Firstly, atom C7 interacts with atom O1. Secondly, atom C13 interacts with atom N3 of the 1,2,4-triazole ring. Atom O2 of the acetyl group forms an intermolecular bifurcated hydrogen bond with the H atoms on ring B (atoms H4 and H5) of a symmetry-related molecule [C4···O2ⁱ = 3.139 (3) Å and C5···O2ⁱ = 3.152 (3) Å; symmetry code: (i) 1 − x,1 − y,1 − z; Fig. 2]. All related details are given in Table 2.

The crystal structure also contains an intermolecular C—H···π contact with the 1,2,4-triazole ring of a symmetry-related molecule at (1 + x,y,z) [C5···Cg1 = 3.694 (3) Å, H5···Cg1 = 3.339 Å and C5—H5···Cg1 = 105°; Cg1 is the centroid of ring A at (1 + x,y,z)], and there are two intermolecular C—H···π interactions, in which atoms C10 and C13 interact with rings B of symmetry-related molecules at (−1 + x,y,z) and (−1 + x,1 + y,z) [C10···Cg2 = 3.633 (3) Å, H10A···Cg2 = 2.793 Å and C10—H10A···Cg2 = 145.45°; Cg2 is the centroid of ring B at (−1 + x,y,z); C13···Cg3 = 3.733 (3) Å, H13B···Cg3 = 3.17° and C13—H13B···Cg3 = 119°; Cg3 is the centroid of ring B at (−1 + x, 1 + y, z)]. These interactions play a role in the structural packing of (I).

S2. Experimental

3-Methyl-4-(para-chlorobenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-one (0.01 mol) was treated with acetic anhydride (10 ml) and the mixture was refluxed for 30 min. After addition of absolute ethanol (30 ml) to the solution, the mixture was refluxed for 1 h. The product was filtered off and dried in vacuo. Several recrystallizations of this product from ethanol gave pure (I) (yield 82%; m.p 454–455 K). IR (KBr, cm⁻¹): ν_C=O: 1769, 1697; ν_C=N: 1623, 1593; ν_{benzoid ring}: 820. ¹H NMR data of (I) (δ/p.p.m. in DMSO-d₆): 2.40 (S, 3H), 2.50 (S, Acetyl, 3H); 7.36 (d, 2H, Ar—H), 7.60(d, 2H, Ar—H), 9.36(S, CH). ¹³C NMR data of (I) (in DMSO-d₆): 166.24 (Acetyl C=O); 155.79 (N=CH), 151.18 (triazole C=O), 148.14, 133.68, 132.95, 132.13(2 C), 131.80(2 C), 23.61, 12.18.

S3. Refinement

H atoms were treated as riding atoms using SHELXL97 defaults.

Computing details

Data collection: CAD-4-PC Software (Enraf-Nonius, 1992); cell refinement: CAD-4-PC Software (Enraf-Nonius, 1992); data reduction: XCAD4 (Harms, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: PLATON (Spek, 1990).

Figures

	Fig. 1. A view of (I), with the atom-numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 50% probability level.
	Fig. 2. The hydrogen-bond network in (I); a view of the triclinic cell.

(I)

Crystal data

C13H13ClN4O2	Z = 2
Mr = 292.72	F(000) = 304
Triclinic, P1	Dx = 1.435 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.341 (2) Å	Cell parameters from 2907 reflections
b = 8.6092 (10) Å	θ = 2.5–26.0°
c = 13.083 (2) Å	µ = 0.29 mm^−1
α = 76.011 (10)°	T = 293 K
β = 84.03 (2)°	Prism, colourless
γ = 78.26 (2)°	0.35 × 0.2 × 0.1 mm
V = 677.4 (3) Å^3

Data collection

Enraf-Nonius CAD-4 Mach-3 diffractometer	Rint = 0.017
Radiation source: fine-focus sealed tube	θmax = 26.0°, θmin = 2.5°
Graphite monochromator	h = 0→7
2θ–ω scans	k = −10→10
2907 measured reflections	l = −16→16
2654 independent reflections	3 standard reflections every 60 min
1818 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)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.144	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0885P)^2 + 0.0264P] where P = (Fo^2 + 2Fc^2)/3
2654 reflections	(Δ/σ)max < 0.001
181 parameters	Δρmax = 0.40 e Å^−3
0 restraints	Δρmin = −0.33 e Å^−3

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All e.s.d.'s are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

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
Cl	1.21109 (12)	−0.05154 (9)	0.15778 (6)	0.0585 (3)
O1	0.2035 (3)	0.5872 (2)	0.44737 (13)	0.0469 (6)
O2	−0.1737 (3)	0.7977 (2)	0.51220 (15)	0.0573 (7)
N1	0.2998 (3)	0.4523 (2)	0.24829 (15)	0.0398 (6)
N2	0.1257 (3)	0.5546 (2)	0.28332 (15)	0.0371 (6)
N3	−0.2004 (3)	0.7048 (2)	0.26735 (15)	0.0393 (6)
N4	−0.1188 (3)	0.7043 (2)	0.36233 (15)	0.0382 (6)
C1	0.6380 (4)	0.2315 (3)	0.1768 (2)	0.0478 (8)
C2	0.8093 (4)	0.1283 (3)	0.1429 (2)	0.0500 (9)
C3	0.9915 (4)	0.0787 (3)	0.2006 (2)	0.0418 (8)
C4	1.0016 (4)	0.1304 (3)	0.29073 (19)	0.0437 (8)
C5	0.8270 (4)	0.2354 (3)	0.32398 (19)	0.0421 (8)
C6	0.6436 (4)	0.2878 (3)	0.26733 (19)	0.0392 (7)
C7	0.4630 (4)	0.3987 (3)	0.30422 (19)	0.0410 (8)
C8	0.0873 (4)	0.6115 (3)	0.37559 (18)	0.0366 (7)
C9	−0.0511 (4)	0.6154 (3)	0.22281 (18)	0.0370 (7)
C10	−0.0586 (4)	0.5838 (3)	0.11698 (19)	0.0453 (8)
C11	−0.2677 (5)	0.6696 (4)	0.0660 (2)	0.0627 (10)
C12	−0.2450 (4)	0.7888 (3)	0.43333 (19)	0.0403 (8)
C13	−0.4678 (4)	0.8631 (3)	0.4014 (2)	0.0510 (9)
H1	0.51480	0.26491	0.13844	0.0574*
H2	0.80354	0.09190	0.08209	0.0600*
H4	1.12449	0.09521	0.32925	0.0525*
H5	0.83321	0.27110	0.38506	0.0505*
H7	0.46681	0.42964	0.36726	0.0492*
H10A	−0.04288	0.46751	0.12329	0.0543*
H10B	0.06162	0.62055	0.07206	0.0543*
H11A	−0.26588	0.64655	−0.00236	0.0940*
H11B	−0.28275	0.78499	0.05859	0.0940*
H11C	−0.38687	0.63173	0.10936	0.0940*
H13A	−0.48826	0.83949	0.33542	0.0766*
H13B	−0.48967	0.97889	0.39367	0.0766*
H13C	−0.56953	0.81884	0.45442	0.0766*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl	0.0485 (4)	0.0585 (4)	0.0657 (5)	0.0076 (3)	−0.0025 (3)	−0.0238 (3)
O1	0.0395 (10)	0.0591 (11)	0.0451 (10)	−0.0013 (8)	−0.0154 (8)	−0.0187 (8)
O2	0.0545 (12)	0.0733 (13)	0.0499 (11)	0.0048 (10)	−0.0170 (9)	−0.0330 (10)
N1	0.0299 (10)	0.0465 (11)	0.0433 (11)	−0.0006 (9)	−0.0049 (9)	−0.0148 (9)
N2	0.0300 (10)	0.0435 (10)	0.0375 (11)	−0.0002 (8)	−0.0059 (8)	−0.0125 (8)
N3	0.0374 (11)	0.0478 (11)	0.0321 (10)	0.0008 (9)	−0.0088 (8)	−0.0122 (9)
N4	0.0338 (10)	0.0459 (11)	0.0356 (10)	0.0017 (9)	−0.0100 (8)	−0.0148 (9)
C1	0.0407 (14)	0.0580 (16)	0.0467 (14)	0.0016 (12)	−0.0172 (11)	−0.0184 (12)
C2	0.0514 (16)	0.0549 (15)	0.0476 (15)	−0.0017 (12)	−0.0137 (12)	−0.0213 (12)
C3	0.0379 (13)	0.0397 (12)	0.0465 (14)	−0.0014 (10)	−0.0033 (11)	−0.0119 (11)
C4	0.0337 (13)	0.0507 (14)	0.0450 (14)	0.0044 (11)	−0.0118 (11)	−0.0135 (12)
C5	0.0383 (14)	0.0506 (14)	0.0388 (13)	−0.0028 (11)	−0.0096 (10)	−0.0143 (11)
C6	0.0324 (12)	0.0418 (13)	0.0419 (13)	−0.0029 (10)	−0.0063 (10)	−0.0081 (10)
C7	0.0362 (13)	0.0469 (14)	0.0406 (13)	−0.0049 (11)	−0.0052 (10)	−0.0124 (11)
C8	0.0338 (12)	0.0402 (12)	0.0365 (12)	−0.0059 (10)	−0.0048 (10)	−0.0099 (10)
C9	0.0343 (12)	0.0413 (12)	0.0349 (12)	−0.0031 (10)	−0.0075 (10)	−0.0088 (10)
C10	0.0406 (14)	0.0578 (16)	0.0361 (13)	0.0015 (12)	−0.0058 (10)	−0.0155 (11)
C11	0.0595 (19)	0.081 (2)	0.0423 (15)	0.0104 (16)	−0.0196 (13)	−0.0166 (14)
C12	0.0408 (13)	0.0411 (13)	0.0404 (13)	−0.0045 (10)	−0.0041 (11)	−0.0139 (10)
C13	0.0390 (14)	0.0641 (17)	0.0543 (16)	0.0013 (12)	−0.0059 (12)	−0.0293 (13)

Geometric parameters (Å, º)

Cl—C3	1.737 (3)	C6—C7	1.456 (4)
O1—C8	1.206 (3)	C9—C10	1.481 (3)
O2—C12	1.193 (3)	C10—C11	1.515 (4)
N1—N2	1.378 (3)	C12—C13	1.485 (4)
N1—C7	1.272 (3)	C1—H1	0.9302
N2—C8	1.390 (3)	C2—H2	0.9294
N2—C9	1.379 (3)	C4—H4	0.9299
N3—N4	1.394 (3)	C5—H5	0.9299
N3—C9	1.278 (3)	C7—H7	0.9299
N4—C8	1.390 (3)	C10—H10A	0.9697
N4—C12	1.403 (3)	C10—H10B	0.9704
C1—C2	1.365 (4)	C11—H11A	0.9603
C1—C6	1.390 (4)	C11—H11B	0.9603
C2—C3	1.383 (4)	C11—H11C	0.9596
C3—C4	1.369 (4)	C13—H13A	0.9603
C4—C5	1.384 (4)	C13—H13B	0.9597
C5—C6	1.382 (4)	C13—H13C	0.9600
Cl···C9^i	3.489 (3)	C13···O1^vii	3.378 (3)
Cl···H13A^ii	3.0092	C1···H10A^iii	3.0666
O1···O2	2.878 (3)	C5···H10A^iii	3.0416
O1···N1	3.058 (3)	C6···H13B^i	3.0030
O1···C7	2.931 (3)	C6···H10A^iii	2.9933
O1···C13^iii	3.378 (3)	C7···H11C^iii	3.0381
O1···C8^iv	3.189 (3)	C8···H7	2.5979
O1···C12^iv	3.206 (3)	C10···H11A^viii	3.0904
O1···N4^iv	3.168 (3)	C13···H4^ix	3.0102
O2···C4^v	3.139 (3)	H1···N1	2.5189
O2···C5^v	3.152 (3)	H1···H11A^viii	2.3834
O2···O1	2.878 (3)	H4···C13^ii	3.0102
O2···C7^iv	3.221 (3)	H4···H13B^ii	2.5929
O1···H5^v	2.7240	H4···O2^v	2.5350
O1···H7	2.2645	H5···H7	2.4461
O1···H13C^iii	2.7095	H5···O1^v	2.7240
O2···H4^v	2.5350	H5···O2^v	2.5529
O2···H5^v	2.5529	H7···O1	2.2645
N1···O1	3.058 (3)	H7···C8	2.5979
N4···O1^iv	3.168 (3)	H7···H5	2.4461
N1···H10A	2.8166	H10A···N1	2.8166
N1···H10B	2.8133	H10A···C1^vii	3.0666
N1···H1	2.5189	H10A···C5^vii	3.0416
N3···H11C	2.7397	H10A···C6^vii	2.9933
N3···H13A	2.1839	H10A···H11A^viii	2.5739
N3···H11B	2.7289	H10B···N1	2.8133
C4···O2^v	3.139 (3)	H11A···C10^viii	3.0904
C5···C9^iii	3.431 (4)	H11A···H1^viii	2.3834
C5···O2^v	3.152 (3)	H11A···H10A^viii	2.5739
C6···C10^iii	3.562 (4)	H11B···N3	2.7289
C7···O2^iv	3.221 (3)	H11C···N3	2.7397
C7···O1	2.931 (3)	H11C···C7^vii	3.0381
C8···C8^iv	3.550 (4)	H13A···Cl^ix	3.0092
C8···O1^iv	3.189 (3)	H13A···N3	2.1839
C9···Cl^vi	3.489 (3)	H13B···C6^vi	3.0030
C9···C5^vii	3.431 (4)	H13B···H4^ix	2.5929
C10···C6^vii	3.562 (4)	H13C···O1^vii	2.7095
C12···O1^iv	3.206 (3)
N2—N1—C7	119.2 (2)	N4—C12—C13	114.5 (2)
N1—N2—C8	131.2 (2)	C2—C1—H1	119.25
N1—N2—C9	119.79 (19)	C6—C1—H1	119.27
C8—N2—C9	109.04 (19)	C1—C2—H2	120.57
N4—N3—C9	104.71 (19)	C3—C2—H2	120.54
N3—N4—C8	112.72 (18)	C3—C4—H4	120.33
N3—N4—C12	120.04 (19)	C5—C4—H4	120.36
C8—N4—C12	127.2 (2)	C4—C5—H5	119.65
C2—C1—C6	121.5 (2)	C6—C5—H5	119.67
C1—C2—C3	118.9 (2)	N1—C7—H7	120.76
Cl—C3—C2	119.3 (2)	C6—C7—H7	120.73
Cl—C3—C4	119.5 (2)	C9—C10—H10A	109.20
C2—C3—C4	121.2 (2)	C9—C10—H10B	109.17
C3—C4—C5	119.3 (2)	C11—C10—H10A	109.23
C4—C5—C6	120.7 (2)	C11—C10—H10B	109.20
C1—C6—C5	118.5 (2)	H10A—C10—H10B	107.90
C1—C6—C7	122.2 (2)	C10—C11—H11A	109.46
C5—C6—C7	119.3 (2)	C10—C11—H11B	109.48
N1—C7—C6	118.5 (2)	C10—C11—H11C	109.49
O1—C8—N2	129.0 (2)	H11A—C11—H11B	109.43
O1—C8—N4	129.6 (2)	H11A—C11—H11C	109.49
N2—C8—N4	101.44 (19)	H11B—C11—H11C	109.48
N2—C9—N3	112.1 (2)	C12—C13—H13A	109.45
N2—C9—C10	122.8 (2)	C12—C13—H13B	109.50
N3—C9—C10	125.1 (2)	C12—C13—H13C	109.47
C9—C10—C11	112.1 (2)	H13A—C13—H13B	109.47
O2—C12—N4	121.0 (2)	H13A—C13—H13C	109.45
O2—C12—C13	124.5 (2)	H13B—C13—H13C	109.49
C7—N1—N2—C8	−2.2 (4)	N3—N4—C12—O2	−175.6 (2)
C7—N1—N2—C9	179.1 (2)	N3—N4—C12—C13	4.4 (3)
N2—N1—C7—C6	178.6 (2)	C8—N4—C12—O2	6.0 (4)
N1—N2—C8—O1	2.3 (4)	C8—N4—C12—C13	−174.0 (2)
N1—N2—C8—N4	−178.2 (2)	C2—C1—C6—C5	−0.8 (4)
C9—N2—C8—O1	−179.0 (3)	C2—C1—C6—C7	179.6 (2)
C9—N2—C8—N4	0.5 (2)	C6—C1—C2—C3	0.3 (4)
N1—N2—C9—N3	178.39 (19)	C1—C2—C3—Cl	−179.6 (2)
N1—N2—C9—C10	−3.8 (3)	C1—C2—C3—C4	0.4 (4)
C8—N2—C9—N3	−0.5 (3)	Cl—C3—C4—C5	179.4 (2)
C8—N2—C9—C10	177.2 (2)	C2—C3—C4—C5	−0.6 (4)
C9—N3—N4—C8	0.1 (3)	C3—C4—C5—C6	0.1 (4)
C9—N3—N4—C12	−178.5 (2)	C4—C5—C6—C7	−179.8 (2)
N4—N3—C9—N2	0.3 (3)	C4—C5—C6—C1	0.5 (4)
N4—N3—C9—C10	−177.4 (2)	C1—C6—C7—N1	−3.9 (4)
N3—N4—C8—O1	179.1 (2)	C5—C6—C7—N1	176.5 (2)
N3—N4—C8—N2	−0.4 (2)	N2—C9—C10—C11	−177.9 (2)
C12—N4—C8—O1	−2.4 (4)	N3—C9—C10—C11	−0.4 (4)
C12—N4—C8—N2	178.1 (2)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···O2^v	0.93	2.54	3.139 (3)	123
C5—H5···O2^v	0.93	2.55	3.152 (3)	123
C7—H7···O1	0.93	2.26	2.931 (3)	128
C13—H13A···N3	0.96	2.18	2.721 (3)	114

Symmetry code: (v) −x+1, −y+1, −z+1.