Arene-perfluoroarene interactions in crystal engineering. 5. Octafluoronaphthalene-tetrathiafulvalene (1/1)

In the title complex, C₁₀F₈·C₆H₄S₄, planar centrosymmetric mol­ecules of tetra­thia­fulvalene and octa­fluoro­naphthalene, inclined to each other by 9.6 (1)°, form a mixed stack which does not exhibit charge transfer. Adjacent stacks pack in a herring-bone motif.

S1. Comment

Octafluoronaphthalene (OFN) forms stable 1:1 co-crystals with a variety of fused-ring aromatic hydrocarbons (Potenza & Mastropaolo, 1975; Collings, Roscoe et al., 2001) and with diphenylacetylene (Collings, Batsanov et al., 2001; Clyburne et al., 2001). The co-crystals comprise mixed stacks of parallel molecules and can be described as molecular complexes, showing no evidence of charge transfer (CT) either in their crystal structures or in UV-visible spectra (CT band). On the other hand, hexafluorobenzene can form genuine CT complexes, e.g. with aromatic amines (Beaumont & Davis, 1967, 1968) or with bis(benzene)chromium (Aspley et al., 1999), although its complexes with non-functionalized arenes also show no CT. To clarify the CT properties of OFN, we prepared its 1:1 complex, (I), with the facile electron donor tetrathiafulvalene (TTF). \sch

The crystal of (I) has a 1:1 TTF·OFN composition. Both molecules (Fig. 1) possess crystallographic C_i symmetry and are planar to within experimental error. They form an infinite stack, parallel to the a axis of the crystal (Fig. 2). The OFN and TTF molecules within a stack are not entirely parallel, but form a dihedral angle of 9.6 (1)°, with an average interplanar separation of 3.45 Å. This distortion may be due to short interstack contacts [F1···F4(x, y - 1, z) 2.827 (2) and F2···F3(-x, y - 1/2, 1/2 - z) 2.858 (2) Å, and their symmetry-related equivalents], compared with the standard van der Waals distance of 2.90 Å (Rowland & Taylor, 1996). In each case, a more parallel alignment of molecules in a stack would generate even shorter F···F contacts, as illustrated in Fig. 2 for the F2···F3 contacts. Adjacent stacks, symmetrically related by a 2₁ axis, have the same general direction, a, but the orientations of TTF planes within them differ by 33.1 (1)°, and the orientations of OFN planes by 48.8 (1)°. No intermolecular contacts, either within or between the stacks, are significantly shorter than the sums of the relevant van der Waals radii (Rowland & Taylor, 1996).

The bond distances in (I) are essentially the same as in crystals of pure TTF (Cooper et al., 1974) and OFN (Batsanov & Collings, 2001), showing the absence of CT in (I), despite the strong electron-donor ability of TTF. To our knowledge, the reduction potential of OFN has not been reported so far. Therefore, we undertook a cyclic voltammetry study of OFN, but observed no redox behaviour whatsoever in the range of 1.0 to -2.0 V. Thus, OFN behaves as an exceedingly poor electron acceptor, notwithstanding the apparent abundance of electronegative atoms in the molecule.

Related literature

For related literature, see: Aspley et al. (1999); Batsanov & Collings (2001); Beaumont & Davis (1967, 1968); Clyburne et al. (2001); Collings, Batsanov, Howard & Marder (2001); Collings, Roscoe, Thomas, Batsanov, Stimson, Howard & Marder (2001); Cooper et al. (1974); Potenza & Mastropaolo (1975); Rowland & Taylor (1996).

S2. Experimental

Slow evaporation of a solution of OFN (0.027 g, 0.1 mmol) and TTF (0.020 g, 0.1 mmol) in CH₂Cl₂ (1 ml) at room temperature, in a vial capped with a needle-pierced septum, for 2–3 d yielded yellow-brown blocks of (I) (m.p. 383–385 K; m.p. for TTF 393–396 K, m.p. for OFN 360–361 K). Gas chromatography and mass spectroscopy on a single-crystal of (I) dissolved in CH₂Cl₂ showed both compounds to be present. Elemental analysis: found (calculated): C 40.05 (40.34), H 0.80 (0.40)%. Cyclic voltammetry measurements were carried out in Bu₄NPF₆ as the supporting electrolyte at 293 K in MeCN, versus an Ag/AgCl reference electrode.

S3. Refinement

The value of R_int fell from 0.047 to 0.029 upon application of the absorption correction.

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 TTF (solid bonds) and OFN (hollow bonds) in (I), projected onto the mean plane of OFN. Displacement ellipsoids are drawn at the 50% probability level. Primed atoms are related through inversion centres to their unprimed equivalents.
	Fig. 2. The crystal packing of (I). H atoms have been omitted for clarity and dashed lines indicate interstack F2···F3 contacts of 2.858 (2) Å.

Octafluoronaphthalene-tetrathiafulvalene (1/1)

Crystal data

C10F8·C6H4S4	Dx = 1.919 Mg m^−3
Mr = 476.43	Melting point = 383–385 K
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 8.581 (3) Å	Cell parameters from 992 reflections
b = 6.321 (2) Å	θ = 12.0–26.4°
c = 15.355 (2) Å	µ = 0.66 mm^−1
β = 98.16 (1)°	T = 120 K
V = 824.4 (4) Å^3	Plate, light brown
Z = 2	0.45 × 0.40 × 0.08 mm
F(000) = 472

Data collection

SMART 1K CCD area-detector diffractometer	2196 independent reflections
Radiation source: fine-focus sealed tube	1967 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
Detector resolution: 8 pixels mm^-1	θmax = 29.0°, θmin = 2.4°
ω scans	h = −11→11
Absorption correction: integration (XPREP in SHELXTL; Bruker, 1997)	k = −8→8
Tmin = 0.763, Tmax = 0.962	l = −20→20
9843 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)] = 0.023	Hydrogen site location: difference Fourier map
wR(F^2) = 0.060	All H-atom parameters refined
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0293P)^2 + 0.3542P] where P = (Fo^2 + 2Fc^2)/3
2196 reflections	(Δ/σ)max = 0.001
135 parameters	Δρmax = 0.35 e Å^−3
0 restraints	Δρmin = −0.23 e Å^−3

Special details

Experimental. The data collection nominally covered over a hemisphere of reciprocal space, by a combination of 5 sets of exposures; each set had a different ϕ and/or 2θ angles and each exposure (10 s) covered 0.3° in ω. Crystal decay was monitored by repeating 50 initial frames at the end of data collection and comparing 144 duplicate reflections.

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
F1	0.19709 (9)	0.14546 (12)	0.43977 (5)	0.02391 (17)
F2	0.21917 (9)	0.39832 (14)	0.30206 (5)	0.02555 (17)
F3	0.08230 (10)	0.78456 (14)	0.28991 (5)	0.02926 (19)
F4	−0.09014 (9)	0.91991 (12)	0.41203 (5)	0.02452 (17)
C1	0.12486 (14)	0.33419 (19)	0.43619 (8)	0.0180 (2)
C2	0.13760 (14)	0.4619 (2)	0.36604 (8)	0.0193 (2)
C3	0.06509 (14)	0.6616 (2)	0.35923 (8)	0.0205 (2)
C4	−0.02138 (14)	0.72853 (19)	0.42206 (8)	0.0185 (2)
C5	−0.03762 (13)	0.60177 (19)	0.49626 (8)	0.0164 (2)
S1	0.45778 (4)	0.33523 (5)	0.621254 (19)	0.01977 (8)
S2	0.39284 (4)	0.77437 (5)	0.55687 (2)	0.02025 (8)
C6	0.46906 (13)	0.52274 (18)	0.53701 (7)	0.0154 (2)
C7	0.37310 (16)	0.5111 (2)	0.68906 (8)	0.0241 (3)
H7	0.351 (2)	0.462 (3)	0.7446 (13)	0.042 (5)*
C8	0.34297 (16)	0.7066 (2)	0.65972 (8)	0.0239 (3)
H8	0.297 (2)	0.817 (3)	0.6906 (12)	0.033 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
F1	0.0229 (4)	0.0186 (4)	0.0312 (4)	0.0040 (3)	0.0071 (3)	−0.0011 (3)
F2	0.0230 (4)	0.0350 (4)	0.0205 (4)	0.0005 (3)	0.0094 (3)	−0.0033 (3)
F3	0.0271 (4)	0.0382 (5)	0.0238 (4)	0.0040 (3)	0.0083 (3)	0.0143 (3)
F4	0.0228 (4)	0.0194 (4)	0.0319 (4)	0.0047 (3)	0.0061 (3)	0.0077 (3)
C1	0.0148 (5)	0.0172 (5)	0.0219 (5)	0.0008 (4)	0.0021 (4)	−0.0017 (4)
C2	0.0148 (5)	0.0263 (6)	0.0173 (5)	−0.0011 (4)	0.0041 (4)	−0.0027 (5)
C3	0.0184 (5)	0.0247 (6)	0.0180 (5)	−0.0015 (5)	0.0019 (4)	0.0059 (5)
C4	0.0151 (5)	0.0179 (5)	0.0223 (6)	0.0005 (4)	0.0013 (4)	0.0032 (4)
C5	0.0139 (5)	0.0173 (5)	0.0177 (5)	−0.0012 (4)	0.0013 (4)	0.0002 (4)
S1	0.02621 (16)	0.01667 (14)	0.01697 (14)	0.00035 (11)	0.00496 (11)	0.00083 (10)
S2	0.02543 (16)	0.01624 (14)	0.02024 (15)	0.00486 (11)	0.00720 (11)	−0.00063 (11)
C6	0.0160 (5)	0.0142 (5)	0.0157 (5)	0.0012 (4)	0.0016 (4)	−0.0001 (4)
C7	0.0291 (7)	0.0274 (7)	0.0177 (6)	−0.0012 (5)	0.0097 (5)	−0.0021 (5)
C8	0.0273 (6)	0.0259 (6)	0.0204 (6)	0.0017 (5)	0.0101 (5)	−0.0052 (5)

Geometric parameters (Å, º)

F1—C1	1.3419 (14)	C5—C5^i	1.437 (2)
F2—C2	1.3459 (13)	S1—C7	1.7501 (13)
F3—C3	1.3431 (14)	S1—C6	1.7672 (12)
F4—C4	1.3452 (14)	S2—C8	1.7472 (13)
C1—C2	1.3628 (17)	S2—C6	1.7628 (13)
C1—C5^i	1.4213 (16)	C6—C6^ii	1.352 (2)
C2—C3	1.4047 (18)	C7—C8	1.328 (2)
C3—C4	1.3652 (17)	C7—H7	0.95 (2)
C4—C5	1.4159 (16)	C8—H8	0.96 (2)
C5—C1^i	1.4213 (16)
F1—C1—C2	118.06 (11)	C4—C5—C5^i	118.46 (13)
F1—C1—C5^i	120.75 (11)	C1^i—C5—C5^i	118.30 (13)
C2—C1—C5^i	121.19 (11)	C7—S1—C6	94.59 (6)
F2—C2—C1	120.58 (12)	C8—S2—C6	94.57 (6)
F2—C2—C3	118.99 (11)	C6^ii—C6—S2	122.48 (12)
C1—C2—C3	120.44 (11)	C6^ii—C6—S1	122.79 (12)
F3—C3—C4	120.83 (12)	S2—C6—S1	114.73 (6)
F3—C3—C2	118.80 (11)	C8—C7—S1	117.81 (10)
C4—C3—C2	120.37 (11)	C8—C7—H7	123.5 (12)
F4—C4—C3	118.13 (11)	S1—C7—H7	118.7 (12)
F4—C4—C5	120.62 (11)	C7—C8—S2	118.28 (10)
C3—C4—C5	121.24 (11)	C7—C8—H8	125.7 (11)
C4—C5—C1^i	123.24 (11)	S2—C8—H8	116.0 (11)

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