6-Phenyl-3-(4-pyrid­yl)-1,2,4-triazolo[3,4-b][1,3,4]thia­diazole

The title compound, C₁₄H₉N₅S, has been synthesized and characterized both spectroscopically and structurally. The triazolo–thia­diazole system, the pyridine ring and the phenyl ring are all planar. The plane of the triazolo–thia­diazole system forms dihedral angles of 1.53 (13) and 7.55 (12)° with the planes of the pyridine and phenyl rings, respectively. In the mol­ecule, there are two intra­molecular inter­actions of types C—H...N and C—H...S. Inter­molecular C—H...N inter­actions involving a phenyl CH group and a triazole N atom lead to the formation of a one-dimensional chain. In the crystal structure, two types of π–π inter­actions affect the packing of the mol­ecules. In addition, there are inter­molecular non-bonded S...N contacts of 2.870 (2) Å, which may cause steric hindrance.

S1. Comment

The prevalence of resistant infections has decreased the applicability of existing chemotherapeutic and chemopreventive antimicrobial agents and stimulated the search for new compounds. The 1,2,4-triazole nucleus and the nitrogen-bridged heterocycles derived from it have recently been incorporated into a variety of compounds with antibacterial (Holla & Kalluraya, 1988), antifungal (Prasad et al., 1989) and antiparasitic (El-Dawy et al., 1983) properties. In addition, it is well known that derivatives of 1,2,4-triazole exhibit anti-inflammatory (Unangst et al., 1992; Mullican et al., 1993), antiviral (Jones et al., 1965), antimicrobial (Shams El-Dine & Hazzaa, 1974; Misato et al., 1977; Koparır et al., 2004) and antidepressant activities (Kane et al., 1988), the last being usually explored by the forced-swim test (Porsolt et al., 1977; Vamvakides, 1990). Among the pharmacological profiles of 1,2,4-triazoles, their antimicrobial, anticonvulsant and antidepressant properties seem to be the best documented. Several thiadiazoles find important application in the fields of medicine, agriculture and industry (Holla, Sarojini & Gonsalves, 1998). 4-Amino-5-substituted-4-yl-4H-1,2,4-triazole-3-thiols have been condensed with aromatic carboxylic acids to yield a series of 6,3-disubstituted-4-yl[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles. Phosphorous oxychloride is used as cyclizing agent (Çetin, 2004; Holla, Gonsalves & Shenoy, 1998). In view of these important properties, the present single-crystal X-ray diffraction study of the title compound, (II), was carried out in order to investigate this bicyclic system and to confirm the assigned structure.

In the present study, the new compound 6-phenyl-3-pyridin-4-yl[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole, (II), was synthesized in 70% yield by the reaction of 4-amino-5-pyridin-4-yl-4H-1,2,4-triazole-3-thiol, (I), benzoic acid and phosphorous oxychloride. The reaction sequences depicted in the scheme were followed to obtain the new compound. The structure of this compound has been confirmed by IR, ¹H NMR and ¹³C NMR spectroscopies.

Compound (II) (Fig. 1) consists of a fused triazolo–thiadiazole system, one pyridine ring and one phenyl ring. The four rings are almost coplanar. As expected, the 1,2,4-triazole and pyridine rings are planar, which can be attributed to a wide range of electron delocalization. The plane of the triazolo–thiadiazole system forms dihedral angles of 1.53 (13) and 7.55 (12)° with the planes of pyridine and phenyl rings, respectively.

The N1═C1 and N2═C2 bond distances [average value 1.315 (2) Å] are in good agreement with those found for structures containing the 1,2,4-triazole ring (Özbey et al., 2000; Bruno et al., 2003). In (II), the presence of the pyridine ring in the 3-position of the triazole ring leads to an elongation of the N1—N2 bond length to 1.395 (2) Å. This bond is 1.371 (2) Å in 5-amino-3-trifluoromethyl-1H-1,2,4-triazole (Borbulevych et al., 1998), in which an electron-withdrawing group is bound to the 3-position of the triazole ring. The thiadiazole moiety displays differences in the pairs of bonds (S1—C2/S1—C3 and C2—N3/C3—N4), due to the fused 1,2,4-triazole ring and the two different groups attached to either side of the triazolo–thiadiazole system. The difference between the S1—C2 [1.724 (2) Å] and S1—C3 [1.7651 (17) Å] bond distances indicates that the resonance effect caused by the triazole ring is stronger than that caused by the thiadiazole ring. The bond distances and angles of the pyridine ring are comparable with those in the literature (Ni et al., 2003).

In the molecular structure, an intramolecular C14—H14···S1 contact leads to the formation of a five-membered ring which is fused with the phenyl ring, while an intramolecular C8—H8···N4 contact leads to the formation of a six-membered ring which is fused with the pyridine ring (Fig. 1). Each of these rings is also fused with the triazolo–thiadiazole system. In the intramolecular C—H···N interaction, the C···N distance is 3.140 (2) Å, a little longer than those in the literature [3.032 (5) Å (Xiang et al., 2004) and 3.063 (3) Å (Özbey et al., 2000)].

In the crystal structure of (II), there are intermolecular C—H···N interactions, leading to a one-dimensional polymer which extends almost along the c axis. In addition to these interactions, the crystal structure contains two π–π stacking interactions. The first of these is between the triazole ring and its symmetry-related partner at (1 − x, 1 − y, −z), with a distance of 3.4594 (11) Å between the ring centroids and a perpendicular distance between the rings of 3.259 (2) Å. The second is between the triazole ring and the pyridine ring at (x, −1 + y, z), with a distance of 3.5029 (13) Å between the ring centroids and a perpendicular distance between the rings of 3.501 (2) Å. The hydrogen-bonding geometry is listed in Table 2. A short contact distance not listed in the tables, yet noteworthy, is S1···N2(1 − x, −y, −z) of 2.870 (2) Å, which may cause steric hindrance.

S2. Experimental

To a mixture of 4-amino-5-pyridin-4-yl-4H-1,2,4-triazole-3-thiol, (I) (5 mmol, 0.965 g), and benzoic acid (1 mmol, 0.61 g.), phosphorous oxychloride (27 mmol, 2.5 ml) was added and and the resulting mixture heated under reflux for 8 h in a water bath. The excess of phosphorous oxychloride was then distilled off and the residue was poured on to crushed ice while stirring. The resulting solid was washed with dilute sodium bicarbonate solution and then recrystallized from dimethyl formamide (yield 70%; m.p. 495–497 K). Spectroscopic analysis: IR (ν, cm⁻¹): 3120–3060 (Ar CH), 1624–1580 (C═ C, C═N), 680 (CH—S—CH); ¹H NMR (400 MHz, DMSO-d₆, δ, p.p.m.): 8.07 (d, J = 7.03 Hz, 2H, o-Ar CH), 7.62–7.69 (m, 3H, m, p-Ar CH), 8.24 (dd, J = 6.23 and 1.47 Hz, 2H, pr C—CH), 8.82 (d, J = 5.87 Hz, 2H, pr N—CH); ¹³C NMR (100 MHz, DMSO-d₆, δ, p.p.m.): 168.36 (C5), 151.46 (C1), 144.39 (C4), 133.69 (C3), 133.07 (C2), 130.43 (C6), 130.20 (C9), 129.50 (C7), 128.08 (C8), 120.16 (C10).

S3. Refinement

The H atoms were located in a difference map and refined isotropically [C—H = 0.94 (2)–1.02 (3) Å].

Computing details

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2002); 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); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2003).

Figures

	Fig. 1. A drawing of compound (II), showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Intramolecular non-bonded C—H···S and C—H···N contacts are represented by dashed lines.
	Fig. 2. The crystal packing of (II), showing the intermolecular C—H···N and π–π interactions (dashed lines).

6-Phenyl-3-(4-pyridyl)-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole

Crystal data

C14H9N5S	F(000) = 576
Mr = 279.32	Dx = 1.487 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 10973 reflections
a = 11.3331 (9) Å	θ = 1.8–27.2°
b = 5.4092 (3) Å	µ = 0.26 mm^−1
c = 20.3509 (18) Å	T = 296 K
β = 90.653 (7)°	Plate, pale yellow
V = 1247.49 (16) Å^3	0.80 × 0.36 × 0.03 mm
Z = 4

Data collection

Stoe IPDS 2 diffractometer	2426 independent reflections
Radiation source: sealed X-ray tube	1642 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.085
Detector resolution: 6.67 pixels mm^-1	θmax = 26.0°, θmin = 2.0°
ω scans	h = −13→13
Absorption correction: integration X-RED32 (Stoe & Cie, 2002)	k = −6→6
Tmin = 0.868, Tmax = 0.989	l = −25→25
13221 measured reflections

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)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.077	All H-atom parameters refined
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0296P)^2] where P = (Fo^2 + 2Fc^2)/3
2426 reflections	(Δ/σ)max = 0.001
217 parameters	Δρmax = 0.16 e Å^−3
0 restraints	Δρmin = −0.21 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
S1	0.35314 (4)	0.06316 (9)	0.08561 (3)	0.04998 (16)
N1	0.41680 (14)	0.4092 (3)	−0.07707 (8)	0.0517 (4)
N2	0.45393 (14)	0.2202 (3)	−0.03505 (8)	0.0520 (4)
N3	0.29686 (12)	0.4020 (3)	0.00560 (8)	0.0434 (4)
N4	0.21156 (13)	0.4277 (3)	0.05255 (8)	0.0463 (4)
N5	0.13944 (17)	1.1184 (3)	−0.14147 (11)	0.0697 (6)
C1	0.32289 (16)	0.5170 (3)	−0.05234 (10)	0.0442 (4)
C2	0.37948 (16)	0.2222 (3)	0.01383 (10)	0.0452 (4)
C3	0.23137 (15)	0.2609 (3)	0.09759 (10)	0.0436 (4)
C4	0.25794 (16)	0.7206 (3)	−0.08231 (10)	0.0465 (4)
C5	0.2935 (2)	0.8154 (4)	−0.14184 (12)	0.0620 (6)
H5	0.356 (2)	0.738 (4)	−0.1670 (12)	0.073 (7)*
C6	0.2315 (2)	1.0103 (5)	−0.16913 (15)	0.0718 (7)
H6	0.259 (2)	1.072 (4)	−0.2111 (14)	0.081 (7)*
C7	0.1062 (2)	1.0248 (4)	−0.08482 (14)	0.0703 (7)
H7	0.034 (2)	1.105 (4)	−0.0648 (13)	0.088 (8)*
C8	0.1608 (2)	0.8298 (4)	−0.05343 (13)	0.0611 (6)
H8	0.1305 (19)	0.763 (4)	−0.0142 (13)	0.074 (7)*
C9	0.15744 (15)	0.2423 (3)	0.15604 (9)	0.0433 (4)
C10	0.07205 (17)	0.4213 (4)	0.16745 (11)	0.0520 (5)
H10	0.0620 (17)	0.557 (4)	0.1360 (11)	0.060 (6)*
C11	0.00415 (19)	0.4110 (4)	0.22291 (11)	0.0572 (5)
H11	−0.0580 (19)	0.536 (4)	0.2291 (11)	0.066 (6)*
C12	0.01970 (18)	0.2227 (4)	0.26783 (11)	0.0555 (5)
H12	−0.0242 (18)	0.212 (3)	0.3065 (12)	0.057 (6)*
C13	0.10276 (18)	0.0440 (4)	0.25656 (12)	0.0569 (5)
H13	0.114 (2)	−0.089 (4)	0.2885 (13)	0.073 (7)*
C14	0.17192 (17)	0.0524 (4)	0.20117 (11)	0.0527 (5)
H14	0.231 (2)	−0.075 (4)	0.1942 (12)	0.074 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0514 (3)	0.0528 (3)	0.0458 (3)	0.0129 (2)	0.0064 (2)	0.0021 (2)
N1	0.0544 (9)	0.0582 (9)	0.0427 (10)	0.0080 (8)	0.0066 (8)	−0.0008 (8)
N2	0.0535 (9)	0.0581 (9)	0.0447 (10)	0.0120 (8)	0.0071 (8)	−0.0001 (8)
N3	0.0425 (8)	0.0476 (8)	0.0404 (9)	0.0067 (6)	0.0062 (7)	−0.0017 (7)
N4	0.0452 (8)	0.0505 (9)	0.0435 (9)	0.0060 (7)	0.0094 (7)	0.0008 (8)
N5	0.0694 (12)	0.0607 (11)	0.0790 (16)	0.0036 (9)	−0.0093 (11)	0.0122 (10)
C1	0.0457 (10)	0.0500 (11)	0.0371 (11)	0.0028 (8)	0.0054 (9)	−0.0016 (8)
C2	0.0460 (9)	0.0463 (10)	0.0435 (11)	0.0082 (8)	0.0050 (9)	−0.0051 (8)
C3	0.0443 (9)	0.0452 (10)	0.0413 (11)	0.0031 (8)	0.0026 (9)	−0.0024 (8)
C4	0.0477 (10)	0.0478 (10)	0.0438 (11)	−0.0003 (8)	−0.0004 (9)	0.0008 (8)
C5	0.0578 (12)	0.0702 (14)	0.0583 (15)	0.0048 (11)	0.0088 (12)	0.0143 (11)
C6	0.0682 (14)	0.0775 (16)	0.0696 (18)	−0.0011 (12)	0.0024 (13)	0.0270 (13)
C7	0.0707 (14)	0.0672 (14)	0.0730 (19)	0.0213 (12)	0.0028 (14)	0.0033 (12)
C8	0.0623 (13)	0.0665 (13)	0.0547 (14)	0.0137 (11)	0.0073 (12)	0.0032 (11)
C9	0.0432 (9)	0.0455 (10)	0.0413 (11)	0.0002 (8)	0.0051 (8)	−0.0003 (8)
C10	0.0564 (11)	0.0489 (11)	0.0510 (13)	0.0077 (9)	0.0127 (10)	0.0069 (10)
C11	0.0599 (12)	0.0571 (12)	0.0547 (14)	0.0083 (10)	0.0144 (11)	0.0025 (10)
C12	0.0520 (11)	0.0694 (13)	0.0454 (13)	−0.0047 (10)	0.0111 (10)	0.0034 (10)
C13	0.0540 (11)	0.0624 (13)	0.0543 (14)	−0.0020 (10)	0.0005 (10)	0.0161 (11)
C14	0.0476 (10)	0.0540 (11)	0.0565 (14)	0.0064 (9)	0.0042 (10)	0.0091 (10)

Geometric parameters (Å, º)

S1—C2	1.724 (2)	C5—H5	0.98 (2)
S1—C3	1.7651 (17)	C6—H6	0.97 (3)
N1—C1	1.318 (2)	C7—C8	1.376 (3)
N1—N2	1.395 (2)	C7—H7	1.02 (3)
N2—C2	1.312 (2)	C8—H8	0.95 (2)
N3—C2	1.359 (2)	C9—C14	1.386 (3)
N3—C1	1.368 (2)	C9—C10	1.390 (2)
N3—N4	1.3740 (19)	C10—C11	1.374 (3)
N4—C3	1.304 (2)	C10—H10	0.98 (2)
N5—C7	1.318 (3)	C11—C12	1.379 (3)
N5—C6	1.327 (3)	C11—H11	0.99 (2)
C1—C4	1.455 (3)	C12—C13	1.371 (3)
C3—C9	1.466 (2)	C12—H12	0.94 (2)
C4—C5	1.380 (3)	C13—C14	1.381 (3)
C4—C8	1.386 (3)	C13—H13	0.98 (2)
C5—C6	1.380 (3)	C14—H14	0.97 (2)
C2—S1—C3	87.58 (9)	C5—C6—H6	116.9 (14)
C1—N1—N2	109.23 (15)	N5—C7—C8	124.6 (2)
C2—N2—N1	105.47 (14)	N5—C7—H7	115.2 (15)
C2—N3—C1	106.05 (14)	C8—C7—H7	120.1 (15)
C2—N3—N4	118.43 (15)	C7—C8—C4	119.0 (2)
C1—N3—N4	135.51 (15)	C7—C8—H8	121.4 (14)
C3—N4—N3	107.56 (14)	C4—C8—H8	119.5 (13)
C7—N5—C6	115.9 (2)	C14—C9—C10	118.85 (17)
N1—C1—N3	108.11 (16)	C14—C9—C3	121.59 (16)
N1—C1—C4	125.56 (17)	C10—C9—C3	119.55 (17)
N3—C1—C4	126.33 (15)	C11—C10—C9	120.43 (19)
N2—C2—N3	111.14 (17)	C11—C10—H10	120.4 (11)
N2—C2—S1	139.23 (15)	C9—C10—H10	119.2 (11)
N3—C2—S1	109.62 (12)	C10—C11—C12	120.38 (19)
N4—C3—C9	121.49 (15)	C10—C11—H11	119.0 (13)
N4—C3—S1	116.80 (13)	C12—C11—H11	120.6 (13)
C9—C3—S1	121.70 (14)	C13—C12—C11	119.54 (19)
C5—C4—C8	117.1 (2)	C13—C12—H12	118.0 (12)
C5—C4—C1	119.84 (17)	C11—C12—H12	122.5 (12)
C8—C4—C1	123.05 (19)	C12—C13—C14	120.7 (2)
C6—C5—C4	119.0 (2)	C12—C13—H13	119.3 (13)
C6—C5—H5	119.3 (14)	C14—C13—H13	119.9 (13)
C4—C5—H5	121.5 (14)	C13—C14—C9	120.09 (19)
N5—C6—C5	124.4 (2)	C13—C14—H14	119.5 (14)
N5—C6—H6	118.7 (14)	C9—C14—H14	120.4 (14)
C1—N1—N2—C2	0.1 (2)	N1—C1—C4—C8	−178.8 (2)
C2—N3—N4—C3	0.1 (2)	N3—C1—C4—C8	2.1 (3)
C1—N3—N4—C3	179.5 (2)	C8—C4—C5—C6	−0.1 (4)
N2—N1—C1—N3	−0.1 (2)	C1—C4—C5—C6	−179.3 (2)
N2—N1—C1—C4	−179.33 (18)	C7—N5—C6—C5	−1.4 (4)
C2—N3—C1—N1	0.0 (2)	C4—C5—C6—N5	1.1 (4)
N4—N3—C1—N1	−179.44 (19)	C6—N5—C7—C8	0.9 (4)
C2—N3—C1—C4	179.27 (19)	N5—C7—C8—C4	0.0 (4)
N4—N3—C1—C4	−0.2 (3)	C5—C4—C8—C7	−0.4 (3)
N1—N2—C2—N3	−0.1 (2)	C1—C4—C8—C7	178.8 (2)
N1—N2—C2—S1	179.02 (19)	N4—C3—C9—C14	174.4 (2)
C1—N3—C2—N2	0.1 (2)	S1—C3—C9—C14	−6.9 (3)
N4—N3—C2—N2	179.62 (15)	N4—C3—C9—C10	−6.8 (3)
C1—N3—C2—S1	−179.33 (13)	S1—C3—C9—C10	171.88 (15)
N4—N3—C2—S1	0.2 (2)	C14—C9—C10—C11	0.7 (3)
C3—S1—C2—N2	−179.5 (2)	C3—C9—C10—C11	−178.14 (19)
C3—S1—C2—N3	−0.33 (14)	C9—C10—C11—C12	−0.2 (3)
N3—N4—C3—C9	178.37 (16)	C10—C11—C12—C13	−0.6 (4)
N3—N4—C3—S1	−0.3 (2)	C11—C12—C13—C14	0.8 (4)
C2—S1—C3—N4	0.42 (16)	C12—C13—C14—C9	−0.3 (3)
C2—S1—C3—C9	−178.31 (17)	C10—C9—C14—C13	−0.4 (3)
N1—C1—C4—C5	0.3 (3)	C3—C9—C14—C13	178.4 (2)
N3—C1—C4—C5	−178.8 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8···N4	0.95 (2)	2.44 (2)	3.112 (3)	128.2 (17)
C14—H14···S1	0.97 (2)	2.73 (2)	3.140 (2)	106.3 (16)
C12—H12···N1^i	0.94 (2)	2.56 (2)	3.452 (3)	160.2 (17)

Symmetry code: (i) x−1/2, −y+1/2, z+1/2.