Octafluoronaphthalene-diphenylacetylene (1/1)

The structure of the title complex, C₁₀F₈·C₁₄H₁₀, comprises mixed stacks of alternating di­phenyl­acetyl­ene and octa­fluoro­naphthalene mol­ecules, both lying at inversion centres and parallel to within 8.6 (1)°, in contrast with the herring-bone packing observed in crystals of either pure component.

S1. Comment

It has been known for a long time that geometrically matching arenes and perfluoroarenes form stable 1:1 molecular complexes with higher melting points than either of the components (Patrick & Prosser, 1960). The crystal structures of these complexes, e.g. hexafluorobenzene-benzene (Williams et al., 1992) or octafluoronaphthalene-naphthalene (Potenza & Mastropaolo, 1975), comprise mixed stacks of approximately parallel arene and perfluoroarene molecules, in contrast with the herringbone structures of the pure components. Recently, there has been a remarkable increase of interest in arene-perfluoroarene interactions, which have been recognized as an important supramolecular synthon (Dai et al., 1999) with potential applications for solid-state chemistry, molecular electronics, liquid crystals etc. For the most important recent experimental and theoretical work and for references to earlier results, see West et al. (1997), Hernandez-Trejillo et al. (1997), Parks et al. (1998), Beck et al. (1998), Coates et al. (1998), Aspley et al. (1999), Weck et al. (1999), Bunz & Enkelmann (1999), Blanchard et al. (2000), Lorenzo et al. (2000), Ponzini et al. (2000), Bartholomew et al. (2000) and Feast et al. (2001).

In the course of our studies on such systems, we found that a perfect geometrical match between the arene and the perfluoroarene is not a necessary condition of equimolar complexation: complexes of octafluoronaphthalene (OFN) with anthracene, phenanthrene, pyrene and triphenylene have been isolated and all were shown by X-ray crystallography to contain mixed stacks (Collings et al., 2001). In order to examine the limits of stability of this motif, we attempted to co-crystallize OFN with increasingly disparate aromatic hydrocarbons. In the course of this work, we prepared the stable (1:1) title complex, (I), formed between OFN and diphenylacetylene (tolan), and its crystal structure is presented here. \sch

Both molecules in complex (I) are located at crystallographic inversion centres (Fig. 1). Thus, both phenyl rings in the tolan molecule are parallel, albeit not exactly co-planar: their planes are separated by 0.06 Å. The OFN molecule is planar within experimental error. The geometry of both molecules is essentially the same as in the crystals of pure OFN (Batsanov & Collings, 2001) and tolan (Mavridis & Moustakali-Mavridis, 1977; Abramenkov et al., 1988; Zanin et al., 1991). This indicates the absence of intermolecular charge transfer, as is usual for most arene-perfluoroarene systems.

The packing motif in (I) is one of mixed stacks of alternating OFN and tolan molecules (Fig. 2), quite different from the herringbone packing of pure tolan and from the flattened herringbone (γ) motif of pure OFN. Within the stack, mean planes of adjacent molecules form a dihedral angle of 8.6 (1)°, with a uniform interplanar separation of 3.39 (7) Å. The direction of the stack is parallel to the crystallographic z axis. Adjacent stacks are shifted relative to each other by approximately c/2, hence the tolan molecules of one stack lie against the OFN molecules of another. Four out of five symmetry-independent H atoms participate in intrastack H···F contacts of 2.61–2.73 Å (calculated for the idealized C—H bond length of 1.08 Å), while H12 forms a shorter H12···F4 contact of 2.43 Å. Although these contacts are not particularly short compared with the standard van der Waals contact distance, variously estimated as 2.55 (Pauling, 1960), 2.67 (Bondi, 1964) or 2.54 Å (Zefirov & Zorkii, 1995; Rowland & Taylor, 1996), they may play a significant role in stabilizing the structure (Dahl, 1990; Thalladi et al., 1998). Interstack contacts between F1 atoms [2.838 (2) Å] are shorter than the standard distance of 2.90 Å (Rowland & Taylor, 1996). The contacting atoms are related via an inversion centre, an orientation which is characteristic for repulsive contacts (Thalladi et al., 1998).

The molecules, which are symmetrically related by a 2₁ axis (and which belong to adjacent stacks, see Fig. 2), are not parallel: the interplanar angle between the OFN molecules is 28.5 (1)° and that between the tolan molecules is 24.4 (1)°. A similar arrangement was observed in OFN-naphthalene (Potenza & Mastropaolo, 1975), where the OFN/naphthalene dihedral angle within the stack is only 3.7°, but the OFN/OFN and naphthalene/naphthalene angles between adjacent stacks are 34.5 and 31.5°, respectively. Both structures can be described as laminar with a residual herring-bone perturbation. However, in the mixed-stack structures of OFN-anthracene, OFN-phenanthrene, OFN-pyrene and OFN-triphenylene, all molecules are parallel to within 10, 3, 0.4 and 1°, respectively (Collings et al., 2001). Thus, there is no simple correlation between the degree of non-coplanarity of stacks and the geometrical mismatch between the arene and the perfluoroarene molecules.

The molecular volume of crystalline OFN at 100 K is 214 ų (Batsanov & Collings, 2001), and that of tolan (extrapolated for 100 K) is ca 250 ų. The volume per formula unit in (I) is 470 ų at the same temperature, indicating an insignificant (1%) decrease of packing density compared with that of the pure components.

The most electron-rich bond of the tolan, C17—C17', is practically eclipsed by the C4'-C5' bond of the OFN (and by the corresponding bond of its inversion equivalent). These bonds are nearly parallel, diverging by 13.6 (2)°, and the resulting contacts C17···C5' [3.370 (2) Å] and C17'···C4' [3.321 (2) Å] are slightly shorter than twice the van der Waals radius of C (3.40–3.59 Å). However, the acetylene moiety remains linear and there is no evidence of electron transfer. Generally, the mode of overlap between the OFN and tolan molecules permits no obvious interpretation in terms of electrostatic interactions.

S2. Experimental

Crystals of (I) were grown by slow evaporation over 3 d at room temperature of a solution of tolan (0.1 mmol, 0.018 g) and OFN (0.1 mmol, 0.027 g) in previously distilled CH₂Cl₂ (2 ml) (m.p. 389–391 K). Analysis: found: C 63.85, H 2.24%; calculated for C₂₄H₁₀F₈: C 64.01, H 2.24%.

S3. Refinement

The range of refined C—H distances was 0.950 (18) to 0.965 (18) Å.

Computing details

Data collection: SMART (Bruker, 1999); cell refinement: SMART; data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The molecules of OFN and tolan in (I), projected on the OFN mean plane. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Primed atoms are symmetrically dependent via inversion centres.
	Fig. 2. The crystal packing of (I). H atoms have been omitted for clarity.

Octafluoronaphthalene-diphenylacetylene (1:1)

Crystal data

C10F8·C14H10	Dx = 1.590 Mg m^−3
Mr = 450.32	Melting point = 389–391 K
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 6.3867 (5) Å	Cell parameters from 552 reflections
b = 20.9583 (17) Å	θ = 12–26°
c = 7.1413 (6) Å	µ = 0.15 mm^−1
β = 100.272 (5)°	T = 100 K
V = 940.57 (13) Å^3	Plate, colourless
Z = 2	0.55 × 0.34 × 0.03 mm
F(000) = 452

Data collection

Siemens SMART 1K CCD area-detector diffractometer	1790 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.033
Graphite monochromator	θmax = 27.5°, θmin = 1.9°
Detector resolution: 8 pixels mm^-1	h = −8→7
ω scans	k = −27→24
5480 measured reflections	l = −9→9
2153 independent 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)] = 0.038	Hydrogen site location: difference Fourier map
wR(F^2) = 0.089	All H-atom parameters refined
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0294P)^2 + 0.4264P] where P = (Fo^2 + 2Fc^2)/3
2153 reflections	(Δ/σ)max = 0.001
165 parameters	Δρmax = 0.26 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

Special details

Experimental. The data collection nominally covered over a hemisphere of reciprocal space, by a combination of 3 sets of ω scans; each set at different ϕ and/or 2θ angles and each scan (20 sec exposure) covering 0.3° in ω. Crystal to detector distance 4.51 cm.

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.

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

	x	y	z	Uiso*/Ueq
C1	0.7672 (2)	0.53654 (7)	0.0820 (2)	0.0239 (3)
C2	0.7345 (2)	0.59753 (8)	0.0188 (2)	0.0258 (3)
C3	0.5330 (2)	0.61660 (7)	−0.0772 (2)	0.0247 (3)
C4	0.3702 (2)	0.57402 (7)	−0.1092 (2)	0.0236 (3)
C5	0.3967 (2)	0.50982 (7)	−0.04907 (19)	0.0214 (3)
F1	0.96084 (13)	0.52082 (4)	0.17969 (13)	0.0315 (2)
F2	0.89188 (15)	0.64062 (4)	0.05018 (14)	0.0341 (2)
F3	0.50495 (16)	0.67720 (4)	−0.13588 (14)	0.0334 (2)
F4	0.17956 (14)	0.59451 (4)	−0.20188 (13)	0.0324 (2)
C11	0.5356 (2)	0.59483 (7)	0.4509 (2)	0.0214 (3)
C12	0.7392 (2)	0.62249 (7)	0.4887 (2)	0.0251 (3)
H12	0.858 (3)	0.5953 (8)	0.537 (3)	0.028 (4)*
C13	0.7646 (3)	0.68675 (8)	0.4523 (2)	0.0288 (3)
H13	0.905 (3)	0.7047 (9)	0.482 (3)	0.033 (5)*
C14	0.5890 (3)	0.72411 (8)	0.3793 (2)	0.0294 (3)
H14	0.604 (3)	0.7681 (9)	0.352 (2)	0.031 (5)*
C15	0.3869 (3)	0.69709 (8)	0.3428 (2)	0.0295 (3)
H15	0.269 (3)	0.7235 (8)	0.290 (2)	0.031 (5)*
C16	0.3593 (2)	0.63280 (7)	0.3772 (2)	0.0250 (3)
H16	0.221 (3)	0.6144 (9)	0.354 (3)	0.033 (5)*
C17	0.5097 (2)	0.52796 (7)	0.4854 (2)	0.0237 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0185 (7)	0.0322 (8)	0.0205 (7)	0.0024 (6)	0.0017 (5)	−0.0043 (6)
C2	0.0244 (7)	0.0304 (8)	0.0238 (7)	−0.0050 (6)	0.0076 (6)	−0.0072 (6)
C3	0.0315 (8)	0.0223 (7)	0.0215 (7)	0.0036 (6)	0.0083 (6)	−0.0017 (6)
C4	0.0216 (7)	0.0290 (8)	0.0195 (7)	0.0069 (6)	0.0021 (5)	−0.0026 (6)
C5	0.0204 (7)	0.0271 (7)	0.0170 (6)	0.0024 (5)	0.0043 (5)	−0.0046 (5)
F1	0.0191 (4)	0.0398 (5)	0.0329 (5)	0.0011 (4)	−0.0027 (4)	−0.0039 (4)
F2	0.0313 (5)	0.0335 (5)	0.0383 (5)	−0.0098 (4)	0.0085 (4)	−0.0066 (4)
F3	0.0418 (6)	0.0237 (5)	0.0353 (5)	0.0038 (4)	0.0092 (4)	0.0010 (4)
F4	0.0259 (5)	0.0356 (5)	0.0331 (5)	0.0093 (4)	−0.0021 (4)	0.0022 (4)
C11	0.0280 (7)	0.0194 (7)	0.0167 (6)	0.0000 (5)	0.0042 (5)	−0.0014 (5)
C12	0.0252 (7)	0.0270 (8)	0.0220 (7)	0.0026 (6)	0.0015 (6)	−0.0021 (6)
C13	0.0278 (8)	0.0286 (8)	0.0294 (8)	−0.0066 (6)	0.0038 (6)	−0.0047 (6)
C14	0.0393 (9)	0.0185 (7)	0.0313 (8)	−0.0023 (6)	0.0085 (7)	0.0005 (6)
C15	0.0316 (8)	0.0252 (8)	0.0308 (8)	0.0056 (6)	0.0034 (6)	0.0034 (6)
C16	0.0243 (7)	0.0260 (8)	0.0241 (7)	−0.0015 (6)	0.0028 (6)	0.0001 (6)
C17	0.0273 (7)	0.0248 (7)	0.0192 (7)	0.0010 (6)	0.0048 (5)	−0.0014 (6)

Geometric parameters (Å, º)

C1—F1	1.3480 (16)	C11—C12	1.405 (2)
C1—C2	1.359 (2)	C11—C17	1.438 (2)
C1—C5^i	1.417 (2)	C12—C13	1.387 (2)
C2—F2	1.3399 (17)	C12—H12	0.965 (18)
C2—C3	1.404 (2)	C13—C14	1.391 (2)
C3—F3	1.3392 (17)	C13—H13	0.958 (18)
C3—C4	1.358 (2)	C14—C15	1.391 (2)
C4—F4	1.3483 (16)	C14—H14	0.950 (19)
C4—C5	1.413 (2)	C15—C16	1.386 (2)
C5—C1^i	1.417 (2)	C15—H15	0.959 (18)
C5—C5^i	1.439 (3)	C16—H16	0.950 (18)
C11—C16	1.402 (2)	C17—C17^ii	1.201 (3)
F1—C1—C2	118.28 (13)	C12—C11—C17	120.00 (13)
F1—C1—C5^i	120.07 (13)	C13—C12—C11	119.99 (14)
C2—C1—C5^i	121.65 (13)	C13—C12—H12	122.0 (10)
F2—C2—C1	120.81 (14)	C11—C12—H12	118.0 (10)
F2—C2—C3	118.99 (14)	C12—C13—C14	120.23 (14)
C1—C2—C3	120.18 (14)	C12—C13—H13	118.4 (11)
F3—C3—C4	121.00 (13)	C14—C13—H13	121.4 (11)
F3—C3—C2	118.84 (13)	C15—C14—C13	120.03 (14)
C4—C3—C2	120.16 (14)	C15—C14—H14	118.7 (11)
F4—C4—C3	118.06 (13)	C13—C14—H14	121.3 (11)
F4—C4—C5	120.07 (13)	C16—C15—C14	120.36 (14)
C3—C4—C5	121.86 (13)	C16—C15—H15	121.0 (11)
C4—C5—C1^i	123.88 (13)	C14—C15—H15	118.6 (11)
C4—C5—C5^i	118.04 (16)	C15—C16—C11	119.94 (14)
C1^i—C5—C5^i	118.08 (17)	C15—C16—H16	120.5 (11)
C16—C11—C12	119.45 (13)	C11—C16—H16	119.6 (11)
C16—C11—C17	120.55 (13)	C17^ii—C17—C11	179.4 (2)

Symmetry codes: (i) −x+1, −y+1, −z; (ii) −x+1, −y+1, −z+1.