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The asymmetric unit of the title compound, C6H6N4, comprises one and a half mol­ecules with a C2 axis through the second mol­ecule. Each mol­ecule consists of two planar five-membered rings connected by a triazole–pyrrole N—N bond with the triazole ring close to being at right angles to the pyrrole ring. The mol­ecules are linked by C—H...N hydrogen bonds and weaker offset face-to-face π–π inter­actions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107020112/ga3049sup1.cif
Contains datablocks IV, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270107020112/ga3049IVsup2.hkl
Contains datablock IV

CCDC reference: 652519

Comment top

1,2,4-Triazole derivatives are a class of organic heterocyclic molecules which are of interest for two main reasons. Firstly, they often show biological, such as antifungal, activity (Sweetman & Martindale, 2005); secondly their iron(II) complexes often exhibit spin crossover behaviour (Klingele, Moubaraki, Cashion, Murray & Brooker, 2005; Haasnoot, 2000; Kahn, 1999). Our interest lies in the latter area and we have been actively developing synthetic routes to carefully designed triazole ligands (Beckmann et al., 2003; Depree et al., 2003; Klingele & Brooker, 2004; Klingele, Moubaraki, Murray & Brooker, 2005; Brandt et al., 2007) for the purpose of accessing novel spin crossover materials (Klingele, Moubaraki, Cashion, Murray & Brooker, 2005). As part of this study, we decided to attempt to oxidize the dialcohol (I) we had prepared earlier (Klingele, Moubaraki, Murray & Brooker, 2005) to the dialdehyde (II) using manganese dioxide (see scheme). As the dialcohol is not very soluble, the reaction was carried out in refluxing 1,4-dioxane, rather than at room temperature. Instead of the dialdehyde (II), compound (IV) as presented here was obtained in high yield.

Compound (IV) has been deliberately prepared previously as part of a study of heterocyclic cations and anions (Katritzky & Suwinski, 1974), as a precursor for the preparation of N-cyanamidoimines (Olofson & Pepe, 1979) and for comparison with other heterocyclic compounds (De Mendoza et al., 1980). In these deliberate preparations it was made by the simple reaction of 4-amino-1,2,4-triazole with 2,5-diethoxytetrahydrofuran in acetic acid. Our accidental synthesis of (IV) from (I) is presumed to have occurred (see scheme) via a combination of over-oxidation, `beyond' (II) to the dicarboxylic acid (III), followed by double decarboxylation, leaving 3,5-unsubstituted (IV). The decarboxylation of acid-substituted triazole rings was first reported in 1907 (Curtius et al., 1907) and a mechanism proposed later (Dyson & Hammick, 1937). The only other structurally characterized (uncoordinated) compound featuring an N4triazole—Npyrrole connection between a 1,2,4-triazole and a pyrrole ring is 3,5-di(2-pyridyl)-N4-(pyrrol-1-yl)triazole (Mandal et al., 1993; Klingele et al., 2006).

The asymmetric unit comprises one and a half molecules as a C2 axis runs through the second molecule (Figs. 1 and 2, and Table 1). Each molecule consists of two planar five-membered rings, viz. one triazole ring and one pyrrole ring, connected by an N4triazole—Npyrrole bond. In both cases, the triazole ring is almost at right angles to the pyrrole ring [the inter-planar angles are 82.43 (8) and 74.41 (7)°, respectively]. The formulation of (IV) is therefore confirmed to be as shown in the scheme. Within experimental error, the bond lengths and angles in the two independent molecules are identical (Table 1). Likewise, the intra-ring torsion angles of the pairs of analgous rings are identical, although the inter-ring torsion angles differ (Table 1).

The bond lengths and angles in the triazole rings (Table 1) are within 0.012 Å of those seen in 4,4'-bitriazole (Domiano, 1977). The bond lengths in the pyrrole rings (Table 1) are within 0.007 Å of those seen in 1H-pyrrole (Allen et al., 1987). The N4triazole—Npyrrole bond lengths (Table 1) are intermediate between those expected for an N—N single bond (1.425 Å) and an N—N double bond (1.240 Å; Allen et al., 1987), indicating that some delocalization is occurring. The N—N inter-ring bond length observed in (IV) is identical to that in 4,4'-bitriazole (1.380 Å; Domiano, 1977).

Weak offset face-to-face ππ interactions (Hunter & Sanders, 1990; Janiak, 2000) with a centroid–centroid distance of 3.507 (2) Å and an angle of 20.2 (1)° between the mean planes, are present between each of the N22/C23/N24/C23A/N22A triazole rings, leading to stacking of these triazole rings along the c axis as shown in Fig. 2. The other triazole ring and the pyrrole rings are not involved in such ππ interactions.

There are three significant C—H···N interactions (Steiner, 1998; Desiraju & Steiner, 1999), all of which are intermolecular (Table 2, Fig. 2). One of these provides further connections between the adjacent, symmetry generated, offset ππ stacked (along the c axis), N22 triazole rings. The remaining two C—H···N interactions link the other independent set of molecules, those containing N1, to their symmetry-generated sets of neighbouring N1 molecules, generating ribbons along the the b axis. The N22 triazoles lie between the ribbons of N1 triazoles.

Related literature top

For related literature, see: Allen et al. (1987); Beckmann et al. (2003); Brandt et al. (2007); Curtius et al. (1907); De Mendoza, Castellanos, Fayet, Vertut & Elguero (1980); Depree et al. (2003); Desiraju & Steiner (1999); Domiano (1977); Dyson & Hammick (1937); Haasnoot (2000); Hunter & Sanders (1990); Janiak (2000); Kahn (1999); Katritzky & Suwinski (1974); Klingele & Brooker (2004); Klingele et al. (2006); Klingele, Moubaraki, Cashion, Murray & Brooker (2005); Klingele, Moubaraki, Murray & Brooker (2005); Mandal et al. (1993); Olofson & Pepe (1979); Steiner (1998); Sweetman & Martindale (2005).

Experimental top

To a partially dissolved mixture of 3,5-bis(hydroxymethyl)-N4-(pyrrol-1-yl)-1,2,4-triazole (2.00 g, 10.3 mmol) in dry 1,4-dioxane (1200 ml, freshly distilled from sodium metal) was added manganese dioxide (10.80 g, from Aldrich). The resulting brown coloured suspension was refluxed for 4 h, then filtered through a pad of Celite on a glass sinter. The filtrate was collected and evaporated to dryness in vacuo, yielding 1.40 g (7.35 mmol, 71%) of an off-white coloured crystalline solid. Single crystals were grown by slow evaporation of an acetone solution of the solid. M.p. 408 K. For other details see supplementary data.

Refinement top

The coordinates and Uiso(H) values for the H atoms were freely refined [C—H = 0.923 (16)–0.978 (15) Å].

Computing details top

Data collection: SMART (Bruker, 2004); cell refinement: SMART and SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2004); software used to prepare material for publication: enCIFer (Version 1.2; Allen et al., 2004).

Figures top
[Figure 1] Fig. 1. Molecular structure and atom-numbering scheme for (IV), with displacement ellipsoids drawn at the 50% probability level and H atoms shown as spheres of arbitrary radii. [Symmetry code: (A) -x, y, -z + 3/2.]
[Figure 2] Fig. 2. The crystal packing of (IV), viewed down the c axis. The C—H···N intermolecular interactions are shown (dashed lines). The stacks of offset face-to-face N22/C23/C24/C23A/N22A triazole rings, weakly ππ stacked along the c axis, can be clearly seen as these triazole rings are almost perpendicular to the c axis.
N4-(Pyrrol-1-yl)-1,2,4-triazole top
Crystal data top
C6H6N4F(000) = 840
Mr = 134.15Dx = 1.381 Mg m3
Monoclinic, C2/cMelting point: 408 K
Hall symbol: -C 2ycMo Kα radiation, λ = 0.71073 Å
a = 22.9326 (11) ÅCell parameters from 5988 reflections
b = 12.1235 (6) Åθ = 2.9–26.4°
c = 7.0111 (3) ŵ = 0.09 mm1
β = 96.707 (2)°T = 93 K
V = 1935.91 (16) Å3Block, colourless
Z = 120.5 × 0.3 × 0.1 mm
Data collection top
Bruker Kappa APEX II area-detector
diffractometer
1997 independent reflections
Radiation source: fine-focus sealed tube1834 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.040
ϕ amd ω scansθmax = 26.5°, θmin = 1.9°
Absorption correction: multi-scan
(SCALE; Bruker, 2004)
h = 2828
Tmin = 0.834, Tmax = 1.000k = 1515
20165 measured reflectionsl = 88
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.036Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.089All H-atom parameters refined
S = 1.10 w = 1/[σ2(Fo2) + (0.0314P)2 + 1.7122P]
where P = (Fo2 + 2Fc2)/3
1997 reflections(Δ/σ)max < 0.001
173 parametersΔρmax = 0.18 e Å3
0 restraintsΔρmin = 0.25 e Å3
Crystal data top
C6H6N4V = 1935.91 (16) Å3
Mr = 134.15Z = 12
Monoclinic, C2/cMo Kα radiation
a = 22.9326 (11) ŵ = 0.09 mm1
b = 12.1235 (6) ÅT = 93 K
c = 7.0111 (3) Å0.5 × 0.3 × 0.1 mm
β = 96.707 (2)°
Data collection top
Bruker Kappa APEX II area-detector
diffractometer
1997 independent reflections
Absorption correction: multi-scan
(SCALE; Bruker, 2004)
1834 reflections with I > 2σ(I)
Tmin = 0.834, Tmax = 1.000Rint = 0.040
20165 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0360 restraints
wR(F2) = 0.089All H-atom parameters refined
S = 1.10Δρmax = 0.18 e Å3
1997 reflectionsΔρmin = 0.25 e Å3
173 parameters
Special details top

Experimental. 1H NMR (500 MHz, CDCl3): 8.44 (2H, s, TrH), 6.88 (2H, t, 3J = 2 Hz, PyrH) and 6.33 (2H, t, 3J = 2 Hz, PyrH) p.p.m.. 13C NMR (125 MHz, CDCl3): 142.4 (Tr), 121.4 (Pyr) and 109.7 (Pyr) p.p.m..

A sample was sublimed by warming to 50°C at <1 m mH g. Microanalysis: C, 53.72; H, 4.56; N, 41.72%. Calc'd for C6H6N4: C, 53.72; H, 4.51; N, 41.77%.

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.

There are no solvent molecules present and there is no disorder. All non-hydrogen atoms were refined anisotropically. The coordinates and U(iso) values for the hydrogen atoms were freely refined.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.17185 (5)0.42851 (9)0.02172 (16)0.0267 (3)
N20.17322 (5)0.34209 (9)0.11132 (15)0.0262 (3)
C30.17229 (5)0.25021 (11)0.01590 (17)0.0225 (3)
H30.1727 (6)0.1748 (12)0.065 (2)0.025 (4)*
N40.17107 (4)0.27229 (8)0.17455 (13)0.0191 (2)
C50.17085 (5)0.38400 (10)0.19046 (18)0.0227 (3)
H50.1690 (6)0.4220 (12)0.307 (2)0.029 (4)*
N110.16928 (4)0.19687 (8)0.32121 (14)0.0197 (2)
C120.12008 (6)0.17326 (11)0.40916 (18)0.0261 (3)
H120.0856 (7)0.2117 (13)0.376 (2)0.035 (4)*
C130.13635 (6)0.09477 (12)0.54369 (18)0.0286 (3)
H130.1108 (7)0.0638 (13)0.628 (2)0.035 (4)*
C140.19646 (6)0.07027 (11)0.53655 (18)0.0253 (3)
H140.2202 (7)0.0188 (13)0.614 (2)0.036 (4)*
C150.21639 (5)0.13478 (10)0.39869 (16)0.0203 (3)
H150.2537 (6)0.1425 (12)0.352 (2)0.025 (4)*
N220.02906 (5)0.57318 (9)0.72689 (16)0.0295 (3)
C230.04474 (6)0.47055 (11)0.71337 (17)0.0250 (3)
H230.0815 (7)0.4429 (12)0.682 (2)0.029 (4)*
N240.00000.40305 (12)0.75000.0223 (3)
N310.00000.28962 (13)0.75000.0267 (3)
C320.02309 (6)0.22582 (13)0.9026 (2)0.0357 (3)
H320.0387 (8)0.2610 (15)1.014 (3)0.044 (5)*
C330.01472 (7)0.11950 (14)0.8446 (3)0.0519 (5)
H330.0266 (9)0.0574 (17)0.920 (3)0.062 (6)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0269 (6)0.0245 (5)0.0273 (6)0.0010 (4)0.0018 (4)0.0033 (4)
N20.0267 (6)0.0298 (6)0.0219 (5)0.0001 (4)0.0016 (4)0.0032 (4)
C30.0232 (6)0.0260 (6)0.0183 (6)0.0004 (5)0.0021 (4)0.0008 (5)
N40.0204 (5)0.0202 (5)0.0163 (5)0.0008 (4)0.0004 (4)0.0013 (4)
C50.0222 (6)0.0214 (6)0.0236 (6)0.0018 (5)0.0019 (5)0.0005 (5)
N110.0206 (5)0.0217 (5)0.0166 (5)0.0000 (4)0.0018 (4)0.0022 (4)
C120.0215 (6)0.0343 (7)0.0230 (6)0.0023 (5)0.0049 (5)0.0022 (5)
C130.0318 (7)0.0354 (7)0.0192 (6)0.0098 (6)0.0055 (5)0.0001 (5)
C140.0321 (7)0.0231 (6)0.0196 (6)0.0031 (5)0.0017 (5)0.0016 (5)
C150.0217 (6)0.0198 (6)0.0186 (5)0.0008 (5)0.0006 (4)0.0012 (4)
N220.0304 (6)0.0291 (6)0.0273 (6)0.0028 (5)0.0037 (4)0.0004 (4)
C230.0232 (6)0.0297 (7)0.0209 (6)0.0026 (5)0.0029 (5)0.0008 (5)
N240.0225 (7)0.0231 (7)0.0205 (7)0.0000.0018 (5)0.000
N310.0242 (8)0.0228 (8)0.0330 (8)0.0000.0030 (6)0.000
C320.0266 (7)0.0342 (8)0.0482 (9)0.0065 (6)0.0122 (6)0.0160 (7)
C330.0402 (9)0.0301 (8)0.0918 (14)0.0082 (7)0.0346 (9)0.0177 (8)
Geometric parameters (Å, º) top
N1—C51.3030 (16)C14—H140.954 (17)
N1—N21.4056 (15)C15—H150.955 (15)
N2—C31.3008 (16)N22—C231.3017 (17)
C3—N41.3653 (15)N22—N22i1.408 (2)
C3—H30.978 (15)C23—N241.3601 (15)
N4—C51.3589 (16)C23—H230.956 (15)
N4—N111.3802 (13)N24—C23i1.3601 (15)
C5—H50.942 (16)N24—N311.375 (2)
N11—C151.3755 (15)N31—C32i1.3753 (17)
N11—C121.3776 (15)N31—C321.3753 (17)
C12—C131.3610 (19)C32—C331.358 (2)
C12—H120.923 (16)C32—H320.926 (18)
C13—C141.4168 (19)C33—C33i1.417 (4)
C13—H130.959 (16)C33—H330.94 (2)
C14—C151.3631 (17)
C5—N1—N2107.34 (10)C15—C14—H14124.1 (10)
C3—N2—N1107.10 (10)C13—C14—H14127.7 (10)
N2—C3—N4109.79 (11)C14—C15—N11106.32 (11)
N2—C3—H3128.2 (9)C14—C15—H15133.4 (9)
N4—C3—H3122.0 (9)N11—C15—H15120.3 (9)
C5—N4—C3106.05 (10)C23—N22—N22i107.08 (7)
C5—N4—N11126.75 (10)N22—C23—N24109.90 (12)
C3—N4—N11127.20 (10)N22—C23—H23127.6 (9)
N1—C5—N4109.73 (11)N24—C23—H23122.5 (9)
N1—C5—H5126.2 (9)C23—N24—C23i106.03 (15)
N4—C5—H5124.1 (9)C23—N24—N31126.99 (8)
C15—N11—C12110.87 (10)C23i—N24—N31126.99 (8)
C15—N11—N4124.50 (10)N24—N31—C32i124.22 (9)
C12—N11—N4124.63 (10)N24—N31—C32124.22 (9)
C13—C12—N11106.43 (11)C32i—N31—C32111.56 (18)
C13—C12—H12133.0 (10)C33—C32—N31105.82 (16)
N11—C12—H12120.4 (10)C33—C32—H32135.8 (11)
C12—C13—C14108.13 (11)N31—C32—H32118.3 (11)
C12—C13—H13124.4 (10)C32—C33—C33i108.40 (11)
C14—C13—H13127.4 (10)C32—C33—H33124.5 (13)
C15—C14—C13108.24 (11)C33i—C33—H33127.1 (13)
C5—N1—N2—C30.71 (13)C12—C13—C14—C150.49 (15)
N1—N2—C3—N40.71 (13)C13—C14—C15—N110.61 (14)
N2—C3—N4—C50.46 (13)C12—N11—C15—C140.53 (14)
N2—C3—N4—N11179.33 (10)N4—N11—C15—C14179.21 (10)
N2—N1—C5—N40.43 (13)N22i—N22—C23—N240.52 (15)
C3—N4—C5—N10.01 (13)N22—C23—N24—C23i0.21 (6)
N11—N4—C5—N1178.87 (10)N22—C23—N24—N31179.79 (6)
C5—N4—N11—C15106.22 (14)C23—N24—N31—C32i97.27 (9)
C3—N4—N11—C1575.14 (16)C23i—N24—N31—C32i82.73 (9)
C5—N4—N11—C1274.08 (16)C23—N24—N31—C3282.73 (9)
C3—N4—N11—C12104.57 (14)C23i—N24—N31—C3297.27 (9)
C15—N11—C12—C130.23 (14)N24—N31—C32—C33179.63 (8)
N4—N11—C12—C13179.51 (11)C32i—N31—C32—C330.37 (8)
N11—C12—C13—C140.16 (14)N31—C32—C33—C33i0.9 (2)
Symmetry code: (i) x, y, z+3/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C5—H5···N1ii0.942 (16)2.353 (16)3.2479 (16)158.6 (12)
C15—H15···N2iii0.955 (15)2.521 (15)3.4261 (16)158.3 (11)
C32—H32···N22ii0.926 (18)2.528 (18)3.325 (2)144.3 (14)
Symmetry codes: (ii) x, y+1, z+1/2; (iii) x+1/2, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC6H6N4
Mr134.15
Crystal system, space groupMonoclinic, C2/c
Temperature (K)93
a, b, c (Å)22.9326 (11), 12.1235 (6), 7.0111 (3)
β (°) 96.707 (2)
V3)1935.91 (16)
Z12
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.5 × 0.3 × 0.1
Data collection
DiffractometerBruker Kappa APEX II area-detector
diffractometer
Absorption correctionMulti-scan
(SCALE; Bruker, 2004)
Tmin, Tmax0.834, 1.000
No. of measured, independent and
observed [I > 2σ(I)] reflections
20165, 1997, 1834
Rint0.040
(sin θ/λ)max1)0.627
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.036, 0.089, 1.10
No. of reflections1997
No. of parameters173
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.18, 0.25

Computer programs: SMART (Bruker, 2004), SMART and SAINT (Bruker, 2004), SAINT (Bruker, 2004), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 2004), enCIFer (Version 1.2; Allen et al., 2004).

Selected geometric parameters (Å, º) top
N1—N21.4056 (15)N22—N22i1.408 (2)
N4—N111.3802 (13)N24—N311.375 (2)
C3—N4—N11—C1575.14 (16)C23—N24—N31—C3282.73 (9)
C5—N4—N11—C1274.08 (16)
Symmetry code: (i) x, y, z+3/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C5—H5···N1ii0.942 (16)2.353 (16)3.2479 (16)158.6 (12)
C15—H15···N2iii0.955 (15)2.521 (15)3.4261 (16)158.3 (11)
C32—H32···N22ii0.926 (18)2.528 (18)3.325 (2)144.3 (14)
Symmetry codes: (ii) x, y+1, z+1/2; (iii) x+1/2, y+1/2, z.
 

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