Photochemical dimerization of a fluorinated di­benzyl­ideneacetone in chloro­form solution

(1E,4E)-1,5-Bis(2,6-di­fluoro­phen­yl)penta-1,4-dien-3-one, C₁₇H₁₀F₄O, (I), dimerizes under sunlight in chloro­form solution to form the corresponding cyclo­butane derivative, (2E,2′E)-1,1′-[2,4-bis­(2,6-di­fluoro­phen­yl)cyclo­butane-1,3-di­yl]bis­[3-(2,6-di­fluoro­phen­yl)prop-2-en-1-one], C₃₄H₂₀F₈O₂, (II). The crystal structure of (I) explains why no topochemical di­merization can occur in the solid state. In the solid, mol­ecules of dimer (II) show the `truxillic acid'-type arrangement of crystallographic centres of inversion, with half a mol­ecule per asymmetric unit and cell dimensions closely related to those of the monomer. Inter­molecular inter­actions in both solids are dominated by C—H...O and C—H...F contacts and also comprise inter­actions with aromatic systems (C—H...π and π–π).

S1. Introduction

Dimerization of olefinic compounds is a common reaction principle in organic synthesis. The photoinduced [2+2] cyclo­addition as the basic mechanism allows the synthesis of natural products (Büchi & Goldman, 1957) and molecules with sophisticated topology otherwise only hardly accessible, e.g. cubanes (Eaton & Cole, 1964) or ladderanes (Hopf, 2003). Photochemical [2+2] cyclo­addition can also occur in the solid state if the double bonds are parallel and separated by less than 4.2 Å (Schmidt, 1971). Therefore, this kind of topochemical control is used rather broadly in the realm of crystal engineering (Biradha & Santra, 2013).

Di­benzyl­ideneacetone, as the parent compound, was investigated several times regarding its photochemical behavior both in solution and in the solid state. It photodimerizes in acetic acid in the presence of uranyl chloride to form a cyclo­butane derived `truxillic'-type dimer (Praetorius & Korn, 1910; Alcock et al., 1975). This kind of dimer is formed due to a head-to-tail orientation of the alkenes during the dimerisation process. In contrast, the 'truxinic' form is based on the head-to-head orientation. In these designations, the head is associated with the phenyl ring and the tail with the moiety containing the carbonyl group. The latter truxinic-type dimer of dibenzalacetone results from the reaction in an iso­propanol/benzene mixture under UV light (Recktenwald et al., 1953). In ethanol solution and using sunlight, a mixture of oligomeric and polymeric compounds and the truxinic form is isolated (Ciamician & Silber, 1909). Furthermore, the reaction in n-hexane solution under N₂ atmosphere with a high pressure Hg lamp as light source leads to the truxinic type dimer (Shoppee et al., 1976).

In the solid state, di­benzyl­ideneacetone is light stable (Green & Schmidt, 1970) with respect to dimerization; rather, it undergoes a photo-induced rearrangement of the double bond (Turowska-Tyrk, 2003). The isomerism of the olefinic moiety with respect to the C═O bond results in two different orientations of the whole molecule. However, adjacent double bonds are not located in a suitably parallel geometry for a [2+2] cyclo­addition in the s olid state.

S2. Experimental

S2.1. Synthesis and crystallization

The synthesis for compound (I) (Scheme 1) was similar to the process described by Williamson (1999) for unsubstituted di­benzyl­ideneacetone. Acetone (0.15 g, 2.5 mmol) and 2,6-di­fluoro­benzaldehyde (0.71 g, 5 mmol) were added to a solution of 0.5 g (12.5 mmol) sodium hydroxide in a mixture of water (5 ml) and ethanol (4 ml). Stirring of the reaction mixture for 30 min at room temperature gave a yellow solid material which was collected via suction filtration. To remove the sodium hydroxide, the raw product was washed with water. Crystallization from ethanol yielded 0.25 g (33%) of yellow crystals [m.p. 409–413 K (ethanol)]. Analysis calculated for C₁₇H₁₀F₄O: C 66.67, H 3.29%; found: C 66.42, H 3.31%. IR (KBr, ν_max, cm^-1): 3053 (w, C_ArH), 1660 (s, C═O), 1624 (s, C═C), 1602 (s, Ph), 1584 (s, Ph). ¹H NMR (400 MHz, CDCl₃): δ 7.83 (2H, d, ²J_HH = 16.4 Hz, C═CHPh), 7.41–7.28 (4H, m, HC═CHPh, Ph), 6.96 (4H, m, Ph). ¹³C NMR (100 MHz, CDCl₃): δ 189.27 (s, C═O), 160.66, 163.21 (d, ¹J_CF = -256.5 Hz, C-2), 131.29 (t, ³J_CF = -11.1 Hz, C═CPh), 130.84 (s, C=CPh), 129.82 (t, ³J_CF = -8.3, C-4), 112.86 (t, ²J_CF = 14.9 Hz, C-1), 111.88 (d, ²J_CF = 26.6 Hz, C-3). ¹⁹F NMR (476 MHz, CDCl₃): δ -110.31 (4F, m). MS (m/e) 306 [M]⁺, 167, 139, 119, 99.

Compound (II) was prepared via irradiation of (I) in chloro­form solution using sunlight. Crystals suitable for X-ray diffraction were grown from ethyl acetate in an optically opaque sample tube. IR (KBr, ν_max, cm^-1): 3100, 3063 (w, C—H), 1690 (s, C═O), 1622 (s, C═C), 1602 (s, Ph), 1585 (s, Ph). ¹H NMR (400 MHz, CDCl₃): δ 7.53 (2H, d, J_HH = 20 Hz, C═CHPh), 7.38–6.77 (14H, m, HC═CHPh, Ph), 5.24 (2H, m, CH), 4.65 (2H, m, CH). ¹³C NMR (100 MHz, CDCl₃): δ 198.0 (s, C═O); 163.1/160.5, 162.8/160.3 (d, ¹J_CF = -256, ¹J_CF = 248 Hz, C1, C5, C13, C17); 131.2–128.6 (m, C═CPh, C═CPh, Ph); 115.3–111.4 (m, Ph); 49.9, 31.6 (s, C10, C11). ¹⁹F NMR (476 MHz, CDCl₃): δ -110.5 (4F, m), -112.6 (4F, m).

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. For compounds (I) and (II), H atoms were positioned geometrically and allowed to ride on their parent atoms, with C—H = 0.95 Å for aryl and olefinic CH groups [U_iso(H) = 1.2U_eq(C)], and C—H = 1.00 Å for aliphatic CH groups [U_iso(H) = 1.5U_eq(C)].

S3. Results and discussion

Although the crystal structure of 1,5-bis­(2,6-di­fluoro­phenyl)­penta-1,4-dien-3-one, (I), has been described previously (Huang et al., 2011), we decided to recollect intensity data at low temperature. We can confirm the previous results in principle, but the higher resolution and lower data collection temperature result in more accurate data; in the following discussion of the photodimerisation process, we therefore refer to our own results. The tetra­fluorinated di­benzyl­ideneacetone crystallizes in the space group P2₁/n with one molecule of C₁ symmetry (Fig. 1a) in general position. The dimer of (I), namely (2E,2'E)-1,1'-[2,4-bis­(2,6-di­fluoro­phenyl)­cyclo­butane-1,3-diyl]bis­[3-(2,6-di­fluoro­phenyl)­prop-2-en-1-one], (II), was found to crystallize in the same space group with similar cell dimensions and the molecule on a centre of inversion (Fig. 2a). The comparison of the cell constants shows the following ratio: a_I ~a_II, b_I \sim c_II and c_I ~b_II. The similarities a_I versus a_II and b_I versus c_II are more pronounced than the relationship between c_I and b_II.

The crystal packing of (I) is dominated by C—H···O and C—H···F inter­actions forming several zigzag chains in the range of 2.3–2.6 Å for the hydrogen-acceptor distance (θ = 145–174°; Table 2). In addition, a π–π stacking inter­action between two adjacent phenyl rings generates molecular dimers. A distance of 3.72 Å and a slippage of 1.47 Å is revealed. These inter­molecular inter­actions have already been observed in the structure reported previously (Huang et al., 2011), but have not been discussed in detail or regarding a photodimerization process. In addition, the bond lengths and therefore the inter­molecular inter­actions are more precise and were found shorter. Furthermore, an additional C—H···F contact is observed existing in the structure (C14—H14···F2; Table 2).

As mentioned above, parallel orientation of the potentially active double bonds and a maximum separation of 4.2 Å have been defined as the basic conditions for a [2+2] cyclo­addition (Schmidt, 1971). The molecular arrangement of di­benzyl­ideneacetone (I) in the solid state does not meet these requirements, and thus this solid is not suitable for a [2+2] cyclo­addition. Instead, the double bonds are located adjacent to an aromatic moiety with a distance of about 3.38 Å and not to a second double bond (Fig. 2a). Therefore, a topochemical transformation of (I) to (II) in the solid state was not expected to be successful. Indeed, crystalline (I) proves to be light stable under sunlight and a UV Hg pressure lamp (100 W). Also, an intended dimerization of compound (I) in CH₂Cl₂ solution using the same conditions under inert atmosphere did not lead to the formation of a dimer but undefined oligo- and polymeric material. A corresponding behavior was found for the irradiation of the parent di­benzyl­ideneacetone in ethanol solution (Ciamician & Silber, 1909). Finally, irradiation of (I) in chloro­form solution using only sunlight gave the dimer. As indicated by the NMR data, two different configurations occur, but only the syn-head–tail orientation could be isolated and proved via single crystal X-ray diffraction (Fig. 2a). Fig. 3 shows the ¹³C NMR spectroscopic data of (I) and (II) in chloro­form for comparison. Signals of the cyclo­butane moiety appear at 49.9 and 31.6 p.p.m., and the chemical shift of the carbonyl group changes from 189.3 to 198.0 p.p.m. in the course of dimerization. In the case of (II), all signals are not distinctly sharp in shape and therefore indicate the formation of at least two different configurations. The crystallographically confirmed configuration of (II) can best be described by the syn-head–tail arrangement of the substituents at the cyclo­butane ring with the aryl group being defined as the head and the carbonyl group containing moiety as the tail (Fig. 2a). All bond lengths and angles are within the range of the expected values both for the cyclo­butane ring and the attached substitutents. The phenyl rings A and B are twisted are twisted with respect to each other with an angle of 63.52 (4)°, whereas the aryl moieties related by an inversion centre (A/A' and B/B') show a parallel orientation for reasons of symmetry.

The crystal packing of (II) is not only dominated by closed-packing and maximum symmetry but also by C—H···O (Desiraju & Steiner, 1999) and C—H···F contacts (Berger et al., 2011). These hydrogen-involved inter­actions are in the range 3.25–3.48 Å for the donor–acceptor distance (θ = 124.6–147.3°) are 2.54–2.65 Å for the hydrogen–acceptor distance. Moreover, there are F···F contacts (Schwarzer & Weber, 2008; Schwarzer et al., 2010) with distances close to the sum of the van der Waals radii [F1···F3(x+1/2, -y-1/2, z+1/2) = 2.9159 (12) Å and F1···F4(-x+3/2, y-1/2, -z+1/2) = 2.9302 (13) Å]. Hence, they might not significantly contribute to a stabilizing effect within the crystal packing. Compound (II) exhibits several aromatic moieties being able to inter­act in inter­molecular inter­actions. In addition to typical C—H···π contacts (Nishio, 2004), π–π stacking inter­actions (Dance, 2004) are localized. They occur between adjacent rings A (atoms C1–C6; symmetry code: -x+1, -y, -z+1), with a distance of 3.65 Å and a slippage of 0.970 Å. The distances of the C—H···π inter­actions are as follows: C7—H7···CgB(-x+1/2, y-1/2, -z+1/2) = 3.662 Å and 141.1°, where CgB as the centroid of the C12–C17 ring (Fig. 1). Relevant C—F···π inter­actions (Berger et al., 2011) are not present in the crystal structure of compound (II).

On the one hand, a comparison of the inter­molecular inter­actions of compounds (I) and (II) reveals minor differences. In both cases, the ortho-substituted H atoms inter­act with either the O atom or the F atom. On the other hand, the aliphatic hydrogen atoms in (II) seem to play a significant role in the packing of (II) as well as the described C–H···π inter­actions which are not present in (I). Moreover, F···F contacts of (II) are not observed in (I).

In conclusion, the light stability of compound (I) in the solid state is in agreement with its crystal structure and (I) readily dimerizes in chloro­form solution under sunlight and reacts under UV light to yield oligo- and polymeric compounds. The cyclo­butane-type dimer is formed with the syn–head–tail orientation, having two olefinic residues thus illustrating that under the given conditions two molecules of (I) have been transformed in a single [2+2] cyclo­addition reaction leaving the second olefinic bond of (I) untouched.

Related literature

For related literature, see: Alcock et al. (1975); Büchi & Goldman (1957); Berger et al. (2011); Biradha & Santra (2013); Ciamician & Silber (1909); Dance (2004); Desiraju & Steiner (1999); Eaton & Cole (1964); Green & Schmidt (1970); Hopf (2003); Huang et al. (2011); Nishio (2004); Praetorius & Korn (1910); Recktenwald et al. (1953); Schmidt (1971); Schwarzer & Weber (2008); Schwarzer et al. (2010); Shoppee et al. (1976); Turowska-Tyrk (2003); Williamson (1999).

Computing details

For both compounds, data collection: SMART (Bruker, 2007); cell refinement: SMART (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXTL (Bruker, 2007); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXL97 (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

(a) Perspective view of (I), showing 50% probability displacement ellipsoids for the non-H atoms. (b) The crystal packing of (I) illustrating the distances between the olefinic double bond and the aromatic unit (right), the bifurcated C—H..O interactions (middle) and the C—H···F interactions (top). [Symmetry codes: (i) -x+5/2, y-1/2, -z+3/2; (ii) -x+3/2, y+1/2, -z+3/2; (iii) -x+3/2, y-1/2, -z+1/2; (iv) -x+3/2, y+1/2, -z+1/2; (v) -x+3/2, y+1/2, -z+3/2; (vi) x+1/2, -y+5/2, z+1/2.]

(a) Perspective view of (II), showing 50% probability displacement ellipsoids for the non-H atoms. The syn-head–tail arrangement of the substituents at the cyclobutane ring is indicated with the aryl group being defined as the head and the carbonyl moiety as the tail. [Symmetry code: (i) -x+1, -y, -z.] (b) Crystal packing of (II) illustrating the intermolecular C—H···O and C—H···F interactions. [Symmetry codes: (iii) x+1/2, -y+1/2, z+1/2; (iv) -x+3/2, y+1/2, -z+1/2; (v) x+1, y+1, z; (vi) x-1/2, -y-1/2, z-1/2].

Comparison of ¹³C NMR data of (I) and (II), indicating the cyclobutane ring formation. R¹ represents 2,6-F₂C₆H₄.

(I) 1,5-Bis(2,6-difluorophenyl)penta-1,4-dien-3-one

Crystal data

C17H10F4O	F(000) = 624
Mr = 306.25	Dx = 1.487 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P2yn	Cell parameters from 1695 reflections
a = 7.4793 (6) Å	θ = 2.2–26.9°
b = 15.6410 (13) Å	µ = 0.13 mm^−1
c = 12.0962 (11) Å	T = 93 K
β = 104.831 (5)°	Needle, yellow
V = 1367.9 (2) Å^3	0.51 × 0.36 × 0.32 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	1849 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.056
Graphite monochromator	θmax = 27.0°, θmin = 2.9°
phi and ω scans	h = −9→8
10280 measured reflections	k = −19→19
2964 independent reflections	l = −12→15

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)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.116	H-atom parameters constrained
S = 0.99	w = 1/[σ^2(Fo^2) + (0.059P)^2] where P = (Fo^2 + 2Fc^2)/3
2964 reflections	(Δ/σ)max = 0.001
199 parameters	Δρmax = 0.22 e Å^−3
0 restraints	Δρmin = −0.25 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
O1	0.95990 (19)	0.88009 (9)	0.72219 (12)	0.0311 (4)
F1	1.28188 (17)	0.62221 (8)	0.75771 (10)	0.0408 (3)
F2	0.96248 (16)	0.68269 (8)	0.37687 (10)	0.0375 (3)
F3	0.62824 (16)	1.05282 (7)	0.35881 (10)	0.0320 (3)
F4	0.71941 (17)	1.15006 (8)	0.73743 (10)	0.0416 (4)
C1	1.2344 (3)	0.60131 (13)	0.64476 (17)	0.0279 (5)
C2	1.3041 (3)	0.52711 (14)	0.6123 (2)	0.0326 (5)
H2	1.3821	0.4909	0.6670	0.039*
C3	1.2570 (3)	0.50662 (14)	0.4971 (2)	0.0326 (5)
H3	1.3043	0.4557	0.4724	0.039*
C4	1.1418 (3)	0.55928 (13)	0.41686 (19)	0.0298 (5)
H4	1.1093	0.5451	0.3379	0.036*
C5	1.0764 (3)	0.63254 (13)	0.45580 (18)	0.0262 (5)
C6	1.1190 (2)	0.65834 (13)	0.56930 (16)	0.0226 (4)
C7	1.0584 (2)	0.73719 (12)	0.61288 (17)	0.0237 (4)
H7	1.0936	0.7435	0.6937	0.028*
C8	0.9598 (2)	0.80204 (12)	0.55473 (17)	0.0227 (4)
H8	0.9172	0.7994	0.4738	0.027*
C9	0.9178 (2)	0.87745 (12)	0.61683 (17)	0.0226 (4)
C10	0.8211 (2)	0.94938 (12)	0.54759 (17)	0.0230 (4)
H10	0.7903	0.9465	0.4665	0.028*
C11	0.7772 (2)	1.01847 (12)	0.59975 (17)	0.0226 (4)
H11	0.8147	1.0170	0.6809	0.027*
C12	0.6802 (2)	1.09605 (12)	0.55061 (16)	0.0218 (4)
C13	0.6070 (2)	1.11323 (13)	0.43514 (16)	0.0229 (4)
C14	0.5135 (3)	1.18678 (13)	0.39291 (17)	0.0259 (5)
H14	0.4659	1.1949	0.3129	0.031*
C15	0.4906 (3)	1.24870 (13)	0.46984 (18)	0.0275 (5)
H15	0.4261	1.2999	0.4423	0.033*
C16	0.5603 (3)	1.23702 (13)	0.58599 (18)	0.0297 (5)
H16	0.5456	1.2797	0.6389	0.036*
C17	0.6515 (3)	1.16191 (13)	0.62293 (17)	0.0267 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0375 (9)	0.0309 (8)	0.0231 (8)	−0.0021 (6)	0.0045 (6)	0.0002 (6)
F1	0.0500 (8)	0.0379 (8)	0.0266 (7)	0.0059 (6)	−0.0045 (6)	0.0035 (6)
F2	0.0419 (8)	0.0433 (8)	0.0243 (7)	0.0150 (6)	0.0028 (5)	0.0012 (6)
F3	0.0388 (7)	0.0344 (7)	0.0223 (7)	0.0067 (5)	0.0069 (5)	−0.0022 (5)
F4	0.0522 (8)	0.0454 (8)	0.0236 (7)	0.0103 (6)	0.0034 (6)	−0.0069 (6)
C1	0.0238 (11)	0.0340 (12)	0.0236 (11)	−0.0050 (8)	0.0017 (8)	0.0035 (9)
C2	0.0227 (11)	0.0294 (12)	0.0414 (14)	0.0004 (9)	0.0006 (9)	0.0059 (10)
C3	0.0213 (11)	0.0308 (12)	0.0478 (15)	0.0001 (8)	0.0125 (10)	−0.0026 (10)
C4	0.0264 (11)	0.0346 (12)	0.0307 (12)	−0.0007 (9)	0.0114 (9)	−0.0022 (10)
C5	0.0187 (10)	0.0302 (12)	0.0294 (12)	0.0026 (8)	0.0057 (8)	0.0057 (9)
C6	0.0136 (10)	0.0280 (11)	0.0261 (11)	−0.0033 (7)	0.0052 (8)	0.0025 (8)
C7	0.0165 (10)	0.0310 (11)	0.0236 (11)	−0.0067 (8)	0.0049 (8)	0.0008 (9)
C8	0.0164 (10)	0.0298 (11)	0.0219 (11)	−0.0052 (8)	0.0047 (8)	0.0003 (8)
C9	0.0144 (10)	0.0290 (11)	0.0242 (11)	−0.0082 (8)	0.0048 (8)	0.0012 (9)
C10	0.0188 (10)	0.0288 (11)	0.0214 (10)	−0.0052 (8)	0.0050 (8)	0.0015 (8)
C11	0.0177 (10)	0.0298 (11)	0.0209 (10)	−0.0078 (8)	0.0058 (8)	−0.0007 (8)
C12	0.0132 (9)	0.0269 (11)	0.0261 (11)	−0.0053 (7)	0.0068 (8)	−0.0001 (8)
C13	0.0186 (10)	0.0274 (11)	0.0246 (11)	−0.0069 (8)	0.0087 (8)	−0.0042 (8)
C14	0.0216 (10)	0.0314 (12)	0.0250 (11)	−0.0032 (8)	0.0063 (8)	0.0025 (9)
C15	0.0198 (11)	0.0265 (11)	0.0375 (13)	−0.0020 (8)	0.0098 (9)	0.0020 (9)
C16	0.0287 (12)	0.0294 (12)	0.0328 (13)	−0.0035 (9)	0.0114 (9)	−0.0072 (9)
C17	0.0240 (11)	0.0343 (12)	0.0208 (11)	−0.0039 (8)	0.0039 (8)	−0.0053 (9)

Geometric parameters (Å, º)

O1—C9	1.233 (2)	C8—C9	1.475 (3)
F1—C1	1.361 (2)	C8—H8	0.9500
F2—C5	1.355 (2)	C9—C10	1.477 (3)
F3—C13	1.359 (2)	C10—C11	1.334 (3)
F4—C17	1.360 (2)	C10—H10	0.9500
C1—C2	1.370 (3)	C11—C12	1.460 (3)
C1—C6	1.404 (3)	C11—H11	0.9500
C2—C3	1.385 (3)	C12—C13	1.390 (3)
C2—H2	0.9500	C12—C17	1.403 (3)
C3—C4	1.391 (3)	C13—C14	1.375 (3)
C3—H3	0.9500	C14—C15	1.384 (3)
C4—C5	1.375 (3)	C14—H14	0.9500
C4—H4	0.9500	C15—C16	1.380 (3)
C5—C6	1.388 (3)	C15—H15	0.9500
C6—C7	1.458 (3)	C16—C17	1.374 (3)
C7—C8	1.342 (3)	C16—H16	0.9500
C7—H7	0.9500
F1—C1—C2	118.09 (18)	C8—C9—C10	117.24 (17)
F1—C1—C6	117.34 (18)	C11—C10—C9	119.53 (18)
C2—C1—C6	124.6 (2)	C11—C10—H10	120.2
C1—C2—C3	117.9 (2)	C9—C10—H10	120.2
C1—C2—H2	121.1	C10—C11—C12	129.61 (19)
C3—C2—H2	121.1	C10—C11—H11	115.2
C2—C3—C4	121.2 (2)	C12—C11—H11	115.2
C2—C3—H3	119.4	C13—C12—C17	113.64 (17)
C4—C3—H3	119.4	C13—C12—C11	126.63 (18)
C5—C4—C3	117.7 (2)	C17—C12—C11	119.72 (18)
C5—C4—H4	121.1	F3—C13—C14	117.79 (17)
C3—C4—H4	121.1	F3—C13—C12	117.66 (17)
F2—C5—C4	117.09 (18)	C14—C13—C12	124.55 (18)
F2—C5—C6	118.20 (17)	C13—C14—C15	118.33 (19)
C4—C5—C6	124.71 (19)	C13—C14—H14	120.8
C5—C6—C1	113.95 (18)	C15—C14—H14	120.8
C5—C6—C7	126.13 (18)	C16—C15—C14	120.82 (19)
C1—C6—C7	119.91 (18)	C16—C15—H15	119.6
C8—C7—C6	129.02 (19)	C14—C15—H15	119.6
C8—C7—H7	115.5	C17—C16—C15	118.10 (19)
C6—C7—H7	115.5	C17—C16—H16	121.0
C7—C8—C9	119.84 (18)	C15—C16—H16	121.0
C7—C8—H8	120.1	F4—C17—C16	118.19 (18)
C9—C8—H8	120.1	F4—C17—C12	117.25 (18)
O1—C9—C8	121.46 (18)	C16—C17—C12	124.56 (19)
O1—C9—C10	121.30 (18)
F1—C1—C2—C3	−179.28 (18)	O1—C9—C10—C11	−0.4 (3)
C6—C1—C2—C3	−0.3 (3)	C8—C9—C10—C11	178.90 (16)
C1—C2—C3—C4	−0.4 (3)	C9—C10—C11—C12	−178.86 (17)
C2—C3—C4—C5	0.2 (3)	C10—C11—C12—C13	1.9 (3)
C3—C4—C5—F2	−179.23 (17)	C10—C11—C12—C17	−179.01 (18)
C3—C4—C5—C6	0.9 (3)	C17—C12—C13—F3	−179.93 (15)
F2—C5—C6—C1	178.63 (17)	C11—C12—C13—F3	−0.7 (3)
C4—C5—C6—C1	−1.5 (3)	C17—C12—C13—C14	−0.5 (3)
F2—C5—C6—C7	−2.6 (3)	C11—C12—C13—C14	178.73 (18)
C4—C5—C6—C7	177.34 (18)	F3—C13—C14—C15	179.83 (16)
F1—C1—C6—C5	−179.83 (17)	C12—C13—C14—C15	0.4 (3)
C2—C1—C6—C5	1.1 (3)	C13—C14—C15—C16	0.2 (3)
F1—C1—C6—C7	1.3 (3)	C14—C15—C16—C17	−0.6 (3)
C2—C1—C6—C7	−177.72 (18)	C15—C16—C17—F4	−179.64 (17)
C5—C6—C7—C8	−3.8 (3)	C15—C16—C17—C12	0.4 (3)
C1—C6—C7—C8	174.96 (19)	C13—C12—C17—F4	−179.88 (16)
C6—C7—C8—C9	−178.40 (17)	C11—C12—C17—F4	0.9 (3)
C7—C8—C9—O1	−5.2 (3)	C13—C12—C17—C16	0.0 (3)
C7—C8—C9—C10	175.51 (17)	C11—C12—C17—C16	−179.20 (18)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···O1^i	0.95	2.32	3.256 (3)	168
C16—H16···O1^ii	0.95	2.31	3.255 (3)	174
C4—H4···F3^iii	0.95	2.58	3.429 (2)	149
C14—H14···F2^iv	0.95	2.49	3.314 (2)	145

Symmetry codes: (i) −x+5/2, y−1/2, −z+3/2; (ii) −x+3/2, y+1/2, −z+3/2; (iii) −x+3/2, y−1/2, −z+1/2; (iv) −x+3/2, y+1/2, −z+1/2.

(II) (2E,2'E)-1,1'-[2,4-Bis(2,6-difluorophenyl)cyclobutane-1,3-diyl]bis[3-(2,6-difluorophenyl)prop-2-en-1-one]

Crystal data

C34H20F8O2	F(000) = 624
Mr = 612.50	Dx = 1.531 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P2yn	Cell parameters from 3206 reflections
a = 7.6508 (2) Å	θ = 2.3–33.3°
b = 11.1075 (3) Å	µ = 0.13 mm^−1
c = 15.6428 (3) Å	T = 93 K
β = 91.572 (1)°	Splitter, colourless
V = 1328.84 (6) Å^3	0.52 × 0.31 × 0.28 mm
Z = 2

Data collection

Bruker SMART CCD area-detector diffractometer	2162 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.019
Graphite monochromator	θmax = 26.0°, θmin = 2.3°
phi and ω scans	h = −9→9
6327 measured reflections	k = −13→11
2576 independent reflections	l = −19→19

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)] = 0.032	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.090	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0464P)^2 + 0.3848P] where P = (Fo^2 + 2Fc^2)/3
2576 reflections	(Δ/σ)max = 0.002
199 parameters	Δρmax = 0.25 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
O1	0.55467 (13)	−0.20126 (9)	0.12309 (6)	0.0260 (2)
F1	0.72649 (12)	−0.25262 (8)	0.41178 (5)	0.0314 (2)
F2	0.61684 (12)	0.15238 (8)	0.33952 (5)	0.0317 (2)
F3	0.18707 (11)	−0.11219 (8)	0.06987 (5)	0.0300 (2)
F4	0.42048 (12)	0.26301 (8)	0.15542 (5)	0.0294 (2)
C1	0.72379 (18)	−0.13448 (13)	0.43378 (9)	0.0240 (3)
C2	0.7663 (2)	−0.10367 (15)	0.51686 (9)	0.0291 (3)
H2	0.8004	−0.1631	0.5577	0.035*
C3	0.7578 (2)	0.01675 (15)	0.53920 (9)	0.0297 (3)
H3	0.7868	0.0405	0.5962	0.036*
C4	0.7074 (2)	0.10325 (14)	0.47938 (9)	0.0287 (3)
H4	0.6997	0.1857	0.4951	0.034*
C5	0.66876 (18)	0.06713 (13)	0.39694 (9)	0.0241 (3)
C6	0.67639 (17)	−0.05240 (13)	0.36965 (8)	0.0212 (3)
C7	0.63852 (17)	−0.09570 (13)	0.28284 (8)	0.0210 (3)
H7	0.6228	−0.1802	0.2771	0.025*
C8	0.62313 (17)	−0.03201 (13)	0.21054 (8)	0.0211 (3)
H8	0.6335	0.0532	0.2120	0.025*
C9	0.58980 (17)	−0.09461 (13)	0.12804 (8)	0.0201 (3)
C10	0.60172 (18)	−0.01498 (12)	0.05015 (8)	0.0196 (3)
H10	0.7163	0.0282	0.0492	0.023*
C11	0.44253 (17)	0.07528 (12)	0.03691 (8)	0.0197 (3)
H11	0.4877	0.1585	0.0273	0.024*
C12	0.30823 (17)	0.07749 (13)	0.10586 (8)	0.0209 (3)
C13	0.30348 (18)	0.17197 (13)	0.16430 (9)	0.0232 (3)
C14	0.1914 (2)	0.17843 (15)	0.23155 (9)	0.0288 (3)
H14	0.1939	0.2456	0.2692	0.035*
C15	0.07498 (19)	0.08464 (15)	0.24295 (9)	0.0291 (3)
H15	−0.0042	0.0874	0.2887	0.035*
C16	0.07356 (19)	−0.01313 (14)	0.18789 (9)	0.0270 (3)
H16	−0.0050	−0.0782	0.1956	0.032*
C17	0.18906 (18)	−0.01376 (13)	0.12149 (9)	0.0234 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0352 (6)	0.0227 (5)	0.0202 (5)	−0.0017 (4)	0.0020 (4)	0.0007 (4)
F1	0.0456 (5)	0.0243 (5)	0.0242 (4)	0.0058 (4)	−0.0025 (4)	0.0020 (4)
F2	0.0485 (5)	0.0240 (5)	0.0224 (4)	0.0019 (4)	−0.0051 (4)	0.0015 (3)
F3	0.0363 (5)	0.0256 (4)	0.0286 (4)	−0.0060 (4)	0.0112 (4)	−0.0044 (4)
F4	0.0388 (5)	0.0242 (4)	0.0253 (4)	−0.0022 (4)	0.0051 (4)	−0.0054 (4)
C1	0.0248 (7)	0.0247 (7)	0.0226 (7)	−0.0001 (6)	0.0012 (5)	0.0015 (6)
C2	0.0321 (8)	0.0337 (8)	0.0212 (7)	−0.0007 (7)	−0.0028 (6)	0.0049 (6)
C3	0.0353 (8)	0.0357 (9)	0.0179 (6)	−0.0060 (7)	−0.0026 (6)	−0.0002 (6)
C4	0.0358 (8)	0.0276 (8)	0.0227 (7)	−0.0042 (6)	0.0006 (6)	−0.0039 (6)
C5	0.0270 (7)	0.0251 (7)	0.0202 (7)	−0.0005 (6)	−0.0002 (5)	0.0043 (6)
C6	0.0199 (6)	0.0258 (7)	0.0179 (6)	−0.0012 (5)	0.0022 (5)	0.0011 (6)
C7	0.0201 (6)	0.0233 (7)	0.0199 (6)	0.0006 (5)	0.0026 (5)	−0.0004 (6)
C8	0.0214 (7)	0.0222 (7)	0.0196 (6)	0.0013 (5)	0.0012 (5)	0.0001 (6)
C9	0.0181 (6)	0.0237 (7)	0.0186 (6)	0.0012 (5)	0.0033 (5)	0.0004 (6)
C10	0.0218 (6)	0.0211 (7)	0.0160 (6)	−0.0001 (5)	0.0027 (5)	−0.0003 (5)
C11	0.0240 (7)	0.0191 (6)	0.0161 (6)	0.0000 (5)	0.0022 (5)	0.0007 (5)
C12	0.0238 (7)	0.0235 (7)	0.0153 (6)	0.0049 (5)	0.0010 (5)	0.0019 (5)
C13	0.0274 (7)	0.0232 (7)	0.0190 (6)	0.0036 (6)	−0.0002 (5)	0.0004 (6)
C14	0.0329 (8)	0.0339 (8)	0.0196 (7)	0.0089 (7)	0.0012 (6)	−0.0052 (6)
C15	0.0263 (7)	0.0419 (9)	0.0194 (7)	0.0085 (7)	0.0066 (6)	0.0028 (6)
C16	0.0238 (7)	0.0333 (8)	0.0241 (7)	0.0024 (6)	0.0046 (5)	0.0038 (6)
C17	0.0263 (7)	0.0237 (7)	0.0205 (6)	0.0041 (6)	0.0021 (5)	−0.0007 (6)

Geometric parameters (Å, º)

O1—C9	1.2168 (17)	C8—H8	0.9500
F1—C1	1.3569 (17)	C9—C10	1.5103 (18)
F2—C5	1.3571 (16)	C10—C11^i	1.5468 (17)
F3—C17	1.3590 (16)	C10—C11	1.5867 (19)
F4—C13	1.3601 (17)	C10—H10	1.0000
C1—C2	1.374 (2)	C11—C12	1.5102 (18)
C1—C6	1.396 (2)	C11—C10^i	1.5468 (17)
C2—C3	1.384 (2)	C11—H11	1.0000
C2—H2	0.9500	C12—C17	1.389 (2)
C3—C4	1.388 (2)	C12—C13	1.3929 (19)
C3—H3	0.9500	C13—C14	1.377 (2)
C4—C5	1.3749 (19)	C14—C15	1.385 (2)
C4—H4	0.9500	C14—H14	0.9500
C5—C6	1.396 (2)	C15—C16	1.386 (2)
C6—C7	1.4620 (18)	C15—H15	0.9500
C7—C8	1.3365 (19)	C16—C17	1.382 (2)
C7—H7	0.9500	C16—H16	0.9500
C8—C9	1.4819 (18)
F1—C1—C2	118.41 (13)	C11^i—C10—C11	90.57 (10)
F1—C1—C6	117.05 (12)	C9—C10—H10	111.4
C2—C1—C6	124.54 (14)	C11^i—C10—H10	111.4
C1—C2—C3	117.88 (14)	C11—C10—H10	111.4
C1—C2—H2	121.1	C12—C11—C10^i	119.94 (11)
C3—C2—H2	121.1	C12—C11—C10	116.87 (11)
C2—C3—C4	120.84 (13)	C10^i—C11—C10	89.43 (10)
C2—C3—H3	119.6	C12—C11—H11	109.7
C4—C3—H3	119.6	C10^i—C11—H11	109.7
C5—C4—C3	118.61 (14)	C10—C11—H11	109.7
C5—C4—H4	120.7	C17—C12—C13	113.90 (12)
C3—C4—H4	120.7	C17—C12—C11	125.20 (12)
F2—C5—C4	117.95 (13)	C13—C12—C11	120.77 (13)
F2—C5—C6	118.36 (12)	F4—C13—C14	117.68 (13)
C4—C5—C6	123.68 (13)	F4—C13—C12	117.65 (12)
C5—C6—C1	114.42 (12)	C14—C13—C12	124.66 (14)
C5—C6—C7	126.00 (13)	C13—C14—C15	118.37 (14)
C1—C6—C7	119.57 (13)	C13—C14—H14	120.8
C8—C7—C6	128.50 (13)	C15—C14—H14	120.8
C8—C7—H7	115.8	C14—C15—C16	120.22 (13)
C6—C7—H7	115.8	C14—C15—H15	119.9
C7—C8—C9	119.85 (13)	C16—C15—H15	119.9
C7—C8—H8	120.1	C17—C16—C15	118.47 (14)
C9—C8—H8	120.1	C17—C16—H16	120.8
O1—C9—C8	123.00 (12)	C15—C16—H16	120.8
O1—C9—C10	122.48 (12)	F3—C17—C16	116.98 (13)
C8—C9—C10	114.52 (12)	F3—C17—C12	118.62 (12)
C9—C10—C11^i	116.11 (11)	C16—C17—C12	124.38 (13)
C9—C10—C11	114.34 (11)
F1—C1—C2—C3	−178.02 (13)	C9—C10—C11—C12	4.49 (17)
C6—C1—C2—C3	1.5 (2)	C11^i—C10—C11—C12	123.67 (14)
C1—C2—C3—C4	0.2 (2)	C9—C10—C11—C10^i	−119.18 (13)
C2—C3—C4—C5	−1.1 (2)	C11^i—C10—C11—C10^i	0.0
C3—C4—C5—F2	178.92 (13)	C10^i—C11—C12—C17	35.36 (19)
C3—C4—C5—C6	0.4 (2)	C10—C11—C12—C17	−70.83 (17)
F2—C5—C6—C1	−177.38 (12)	C10^i—C11—C12—C13	−149.23 (13)
C4—C5—C6—C1	1.2 (2)	C10—C11—C12—C13	104.58 (15)
F2—C5—C6—C7	2.1 (2)	C17—C12—C13—F4	177.66 (11)
C4—C5—C6—C7	−179.36 (14)	C11—C12—C13—F4	1.76 (19)
F1—C1—C6—C5	177.41 (12)	C17—C12—C13—C14	−0.8 (2)
C2—C1—C6—C5	−2.2 (2)	C11—C12—C13—C14	−176.71 (13)
F1—C1—C6—C7	−2.09 (19)	F4—C13—C14—C15	−178.12 (12)
C2—C1—C6—C7	178.33 (13)	C12—C13—C14—C15	0.4 (2)
C5—C6—C7—C8	14.1 (2)	C13—C14—C15—C16	0.4 (2)
C1—C6—C7—C8	−166.42 (14)	C14—C15—C16—C17	−0.7 (2)
C6—C7—C8—C9	177.94 (13)	C15—C16—C17—F3	178.53 (12)
C7—C8—C9—O1	9.0 (2)	C15—C16—C17—C12	0.2 (2)
C7—C8—C9—C10	−171.38 (12)	C13—C12—C17—F3	−177.80 (11)
O1—C9—C10—C11^i	2.97 (19)	C11—C12—C17—F3	−2.1 (2)
C8—C9—C10—C11^i	−176.65 (11)	C13—C12—C17—C16	0.5 (2)
O1—C9—C10—C11	106.49 (15)	C11—C12—C17—C16	176.24 (13)
C8—C9—C10—C11	−73.12 (14)

Symmetry code: (i) −x+1, −y, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···O1^ii	0.95	2.64	3.4817 (18)	147
C14—H14···O1^iii	0.95	2.64	3.2766 (17)	125
C2—H2···F3^ii	0.95	2.65	3.3232 (18)	128
C3—H3···F4^iv	0.95	2.57	3.2733 (18)	131
C11—H11···F1^v	1.00	2.56	3.2557 (16)	127
C10—H10···F1^v	1.00	2.54	3.2452 (16)	127

Symmetry codes: (ii) x+1/2, −y−1/2, z+1/2; (iii) −x+1/2, y+1/2, −z+1/2; (iv) x+1/2, −y+1/2, z+1/2; (v) −x+3/2, y+1/2, −z+1/2.