Diortho­benzeno­tetra(5',2'-tetrazolo)[5'-(2)-2'-(6)]­cyclo­phane

The first structure of the tetra-tetrazole macrocycle diortho­benzeno­tetra(5',2'-tetrazolo)[5'-(2)-2'-(6)]­cyclo­phane, C₂₈H₃₂N₁₆, has been determined. The interior of the rectangular cavity measures ca 11.2 × 5.7 Å.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.037
• wR factor = 0.098
• Data-to-parameter ratio = 11.2

checkCIF results

No syntax errors found



ADDSYM reports no extra symmetry


 Alert Level B:



THETM_01  Alert B The value of sine(theta_max)/wavelength is less than 0.575
          Calculated sin(theta_max)/wavelength =    0.5714

Author response: ... This data set was collected at a time when we routinely used a theta max value of 22 degrees and this was the publication 'norm'. In the case of this particular structure, we collected 2 additional degrees of data (theta max = 24 degrees) because of the crystal quality. We used this cut-off largely because we could see that the data were good, as exemplified by the esds on the geometric parameters, and also because of the fall-off in diffracted intensities at higher Bragg angles.

 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

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S1. Comment

We have been interested for some time in the synthesis of compounds with multiple tetrazole fragments (Bethel et al., 1999; Bhandari et al., 1999; Butler et al., 1992; Butler & Fleming, 1997; Butler & NíBhrádaigh, 1994). One of us (RNB) has succeeded in generating tetratetrazole macrocyles of general formula (I) which include an apparent cavity of variable dimensions tailored by both the length and flexibility of the bridging groups X and Y (Butler & NíBhrádaigh, 1994; Butler et al., 1992; Butler & Fleming, 1997). Such macrocycles represent an extension of other work which has led to the isolation of polyazole macrocycles containing pyrazole (Tarrago et al., 1988) and triazole (Gal et al., 1985; Cabezon et al., 1995).

The structure of diorthobenzenotetra(5',2'-tetrazolo)[5'-(2)–2'-(6)]cyclophane [(I), X = 1,2-C₆H₄, Y = (CH₂)₆] is now reported (Fig. 1). The molecule is centrosymmetric about the inversion centre at 1/2, 1/2, 1/2, which is intrinsic in the space-group symmetry. Of central importance is the rectangular nature of the macrocyle cavity, which measures ca 11.228 (3) (C14—N5') by 5.678 (4) Å (C8—C8'), which is the first structure of a macrocycle containing four sub-tetrazole rings surrounding such a feature. Cyclophanes with two tetrazole rings have been reported (Ried & Aboul-Fetouh, 1988; Ried et al., 1989; Bethel et al., 1999), but such systems do not constitute a cavity. The central void depicted in Fig. 1 is more apparent than real, as a space-filling representation (Fig. 2) illustrates. While there is clearly a void channel running parallel to, and between, the (CH₂)₆ chains, the orientations of the potentially coordinating tetrazole units are orthogonal to this channel. Much smaller voids are evident between pairs of tetrazoles attached to the same C₆H₄ unit (Fig. 2), though nitrogen lone pairs from each heterocycle are approximately at right angles to each other (see below) and are not oriented for concerted metal-ion complexation.

Of the two unique tetrazoles, one is essentially coplanar with the phenyl group to which it is attached (torsion angle between ring planes 9.58°), while the other is approximately orthogonal (torsion angle 97.51°). This allows symmetry-related pairs of tetrazoles to adopt cofacial orientations with respect to each other across opposite sides of the rectangle. In other structures containing tetrazoles bonded at the ortho positions of a six-membered aromatic system, the two heterocycles are also found to be twisted with respect to the central ring (Bethel at al., 1999). In one case, 2-(1,2)benzo-1(5,1),3(5,2)-bistetrazolocyclodecaphane, the twist angles (7.7 and 85.6°) are very similar to those found in the title compound (Ried & Aboul-Fetouh, 1988). Overall the macrocyle exists in a chair conformation with the -(CH₂)₆– linkages adopting a surprisingly rigid linear conformation (Fig. 1). Such a structure has been predicted by energy minimization calculations for the more rigid analogue of the title compound, (I) (X = 1,3-C₆H₄, Y = 1,4-C₆H₄), but was not anticipated for the title compound (Butler & Fleming, 1997).

S2. Experimental

The title compound was synthesized according to the literature method of Butler & NiBhradaigh (1994). Crystals suitable for X-ray diffraction were grown from dichloromethane/pentane (1:1).

S3. Refinement

It was possible to positionally refine all H-atom positions in this crystal structure. However, as `free' refinement yielded a final position which was close (within the bounds of experimental error) to the calculated positions, we ultimately refined the H atoms riding on their relevant parent atoms.

Computing details

Data collection: CAD-4-PC Software (Enraf-Nonius, 1992); cell refinement: CELDIM in CAD-4-PC Software; data reduction: XCAD (McArdle & Higgins, 1995); program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL93 (Sheldrick, 1993); molecular graphics: ORTEX (McArdle, 1995).

Figures

	Fig. 1. ORTEX plot of the asymmetric unit of diorthobenzenotetra(5',2'-tetrazolo)[5'-(2)–2'-(6)]cyclophane showing the labelling scheme. Ellipsoids are represented at the 30% probability level. Primed labelled atoms are related to unprimed labelled atoms by the 1 - x, 1 - y, 1 - z symmetry operation.
	Fig. 2. Space-filling stereoview of diorthobenzenotetra(5',2'-tetrazolo)[5'-(2)–2'-(6)]cyclophane showing the restricted nature of the macrocycle cavity.

(93kcm4)

Crystal data

C28H32N16	Z = 1
Mr = 592.70	F(000) = 312
Triclinic, P1	Dx = 1.367 Mg m^−3
a = 7.170 (2) Å	Mo Kα radiation, λ = 0.71069 Å
b = 10.241 (3) Å	Cell parameters from 25 reflections
c = 10.729 (3) Å	θ = 13.9–17.7°
α = 77.25 (3)°	µ = 0.09 mm^−1
β = 74.89 (3)°	T = 293 K
γ = 73.47 (3)°	Block, colourless
V = 719.9 (4) Å^3	0.35 × 0.30 × 0.30 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	Rint = 0.010
Radiation source: fine-focus sealed tube	θmax = 24.0°, θmin = 2.1°
Graphite monochromator	h = 0→8
θ/2θ scans	k = −11→11
2441 measured reflections	l = −11→12
2238 independent reflections	1 standard reflections every 80 reflections
1674 reflections with I > 2σ(I)	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.037	H-atom parameters constrained
wR(F^2) = 0.098	w = 1/[σ^2(Fo^2) + (0.0714P)^2 + 0.0022P] where P = (Fo^2 + 2Fc^2)/3
S = 1.08	(Δ/σ)max < 0.001
2238 reflections	Δρmax = 0.17 e Å^−3
200 parameters	Δρmin = −0.13 e Å^−3
0 restraints	Extinction correction: SHELXL93, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0608 (71)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
N1	0.2292 (2)	0.31148 (15)	0.60411 (13)	0.0527 (4)
N2	0.2397 (2)	0.43564 (15)	0.53809 (14)	0.0559 (4)
N3	0.2452 (2)	0.43014 (14)	0.41642 (14)	0.0498 (4)
N4	0.2409 (2)	0.30851 (14)	0.39627 (13)	0.0501 (4)
N5	0.8191 (2)	0.87060 (13)	0.04860 (12)	0.0450 (4)
N6	0.7094 (2)	0.93678 (14)	0.14675 (13)	0.0456 (4)
N7	1.0277 (2)	0.86172 (15)	0.15889 (13)	0.0492 (4)
N8	1.0089 (2)	0.8249 (2)	0.05300 (13)	0.0516 (4)
C1	0.2314 (2)	0.0877 (2)	0.54015 (15)	0.0398 (4)
C2	0.2699 (2)	0.0224 (2)	0.4327 (2)	0.0477 (4)
H2	0.2921	0.0728	0.3490	0.057*
C3	0.2757 (3)	−0.1152 (2)	0.4474 (2)	0.0547 (5)
H3	0.2993	−0.1565	0.3739	0.066*
C4	0.2469 (3)	−0.1926 (2)	0.5705 (2)	0.0556 (5)
H4	0.2513	−0.2859	0.5806	0.067*
C5	0.2115 (2)	−0.1294 (2)	0.6784 (2)	0.0500 (5)
H5	0.1941	−0.1815	0.7614	0.060*
C6	0.2014 (2)	0.0102 (2)	0.6658 (2)	0.0408 (4)
C7	0.2308 (2)	0.2356 (2)	0.51581 (14)	0.0408 (4)
C8	0.2703 (3)	0.5443 (2)	0.3086 (2)	0.0582 (5)
H8A	0.2363	0.6298	0.3435	0.070*
H8B	0.1807	0.5534	0.2516	0.070*
C9	0.4837 (3)	0.5195 (2)	0.2303 (2)	0.0549 (5)
H9A	0.5718	0.5112	0.2881	0.066*
H9B	0.5173	0.4326	0.1981	0.066*
C10	0.5207 (3)	0.6315 (2)	0.1161 (2)	0.0547 (5)
H10A	0.4839	0.7194	0.1471	0.066*
H10B	0.4380	0.6376	0.0555	0.066*
C11	0.7370 (3)	0.6029 (2)	0.0461 (2)	0.0552 (5)
H11A	0.7743	0.5116	0.0220	0.066*
H11B	0.8171	0.6014	0.1069	0.066*
C12	0.7894 (3)	0.7052 (2)	−0.0763 (2)	0.0589 (5)
H12A	0.9314	0.6781	−0.1116	0.071*
H12B	0.7215	0.6990	−0.1413	0.071*
C13	0.7366 (3)	0.8532 (2)	−0.0557 (2)	0.0529 (5)
H13A	0.7864	0.9092	−0.1364	0.063*
H13B	0.5929	0.8859	−0.0345	0.063*
C14	0.1567 (2)	0.0712 (2)	0.78545 (14)	0.0401 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0734 (10)	0.0496 (9)	0.0382 (8)	−0.0257 (7)	−0.0058 (7)	−0.0059 (7)
N2	0.0742 (11)	0.0500 (9)	0.0452 (9)	−0.0238 (7)	−0.0042 (7)	−0.0092 (7)
N3	0.0604 (9)	0.0440 (8)	0.0444 (8)	−0.0192 (7)	−0.0048 (6)	−0.0044 (6)
N4	0.0668 (10)	0.0451 (8)	0.0401 (8)	−0.0198 (7)	−0.0110 (7)	−0.0024 (6)
N5	0.0532 (9)	0.0438 (8)	0.0376 (7)	−0.0147 (6)	−0.0107 (6)	−0.0004 (6)
N6	0.0470 (8)	0.0505 (8)	0.0393 (8)	−0.0126 (6)	−0.0094 (6)	−0.0056 (6)
N7	0.0461 (8)	0.0565 (9)	0.0438 (8)	−0.0109 (7)	−0.0097 (6)	−0.0069 (7)
N8	0.0498 (9)	0.0584 (9)	0.0445 (8)	−0.0114 (7)	−0.0075 (6)	−0.0086 (7)
C1	0.0382 (9)	0.0440 (9)	0.0388 (9)	−0.0127 (7)	−0.0091 (7)	−0.0047 (7)
C2	0.0542 (10)	0.0520 (10)	0.0397 (9)	−0.0167 (8)	−0.0118 (7)	−0.0057 (7)
C3	0.0610 (11)	0.0540 (11)	0.0548 (11)	−0.0132 (8)	−0.0148 (8)	−0.0180 (9)
C4	0.0587 (12)	0.0410 (9)	0.0698 (13)	−0.0123 (8)	−0.0179 (9)	−0.0086 (9)
C5	0.0524 (10)	0.0464 (10)	0.0494 (11)	−0.0152 (8)	−0.0125 (8)	0.0025 (8)
C6	0.0357 (8)	0.0437 (9)	0.0431 (9)	−0.0118 (7)	−0.0097 (7)	−0.0023 (7)
C7	0.0406 (9)	0.0472 (9)	0.0364 (9)	−0.0156 (7)	−0.0064 (7)	−0.0056 (7)
C8	0.0745 (13)	0.0425 (10)	0.0513 (11)	−0.0182 (8)	−0.0058 (9)	0.0017 (8)
C9	0.0591 (11)	0.0491 (10)	0.0564 (11)	−0.0204 (8)	−0.0122 (9)	0.0017 (8)
C10	0.0612 (11)	0.0477 (10)	0.0518 (11)	−0.0154 (8)	−0.0087 (8)	−0.0021 (8)
C11	0.0607 (12)	0.0470 (10)	0.0565 (11)	−0.0173 (8)	−0.0059 (9)	−0.0079 (8)
C12	0.0685 (12)	0.0636 (12)	0.0470 (10)	−0.0250 (10)	−0.0031 (9)	−0.0126 (9)
C13	0.0689 (12)	0.0566 (11)	0.0384 (9)	−0.0233 (9)	−0.0188 (8)	0.0014 (8)
C14	0.0434 (9)	0.0410 (8)	0.0349 (8)	−0.0148 (7)	−0.0093 (7)	0.0031 (7)

Geometric parameters (Å, º)

N1—N2	1.324 (2)	C1—C7	1.479 (2)
N1—C7	1.347 (2)	C2—C3	1.372 (2)
N2—N3	1.309 (2)	C3—C4	1.380 (3)
N3—N4	1.320 (2)	C4—C5	1.381 (2)
N3—C8	1.467 (2)	C5—C6	1.388 (2)
N4—C7	1.329 (2)	C6—C14	1.472 (2)
N5—N8	1.318 (2)	C8—C9	1.522 (2)
N5—N6	1.329 (2)	C9—C10	1.506 (2)
N5—C13	1.458 (2)	C10—C11	1.512 (2)
N6^i—C14	1.323 (2)	C11—C12	1.524 (3)
N7—N8	1.322 (2)	C12—C13	1.506 (3)
N7^i—C14	1.352 (2)	C14^i—N6	1.323 (2)
C1—C2	1.387 (2)	C14^i—N7	1.352 (2)
C1—C6	1.403 (2)
N2—N1—C7	106.1 (1)	C3—C4—C5	119.0 (2)
N3—N2—N1	106.1 (1)	C4—C5—C6	121.6 (2)
N2—N3—N4	114.2 (1)	C5—C6—C1	118.9 (2)
N2—N3—C8	123.7 (1)	C5—C6—C14	118.5 (1)
N4—N3—C8	122.0 (1)	C1—C6—C14	122.7 (1)
N3—N4—C7	102.0 (1)	N4—C7—N1	111.8 (1)
N8—N5—N6	113.9 (1)	N4—C7—C1	121.3 (1)
N8—N5—C13	123.3 (1)	N1—C7—C1	126.9 (1)
N6—N5—C13	122.8 (1)	N3—C8—C9	110.8 (2)
C14^i—N6—N5	101.9 (1)	C10—C9—C8	114.0 (2)
N8—N7—C14^i	106.1 (1)	C9—C10—C11	111.1 (2)
N5—N8—N7	106.0 (1)	C10—C11—C12	115.7 (2)
C2—C1—C6	118.9 (1)	C13—C12—C11	114.9 (2)
C2—C1—C7	117.9 (1)	N5—C13—C12	112.4 (2)
C6—C1—C7	123.2 (1)	N6^i—C14—N7^i	112.1 (1)
C3—C2—C1	121.3 (2)	N6^i—C14—C6	124.1 (1)
C2—C3—C4	120.4 (2)	N7^i—C14—C6	123.8 (1)

Symmetry code: (i) −x+1, −y+1, −z+1.