Monitoring photo-induced transformations in crystals of 2,6-di­fluoro­cinnamic acid under ambient conditions

Several conditions need to be fulfilled for a photochemical reaction to proceed in crystals. Some of these conditions, for example, geometrical conditions, depend on the particular type of photochemical reaction, but the rest are common for all reactions. The mutual directionality of two neighbouring mol­ecules determines the kind of product obtained. The influence of temperature on the probability of a photochemical reaction occurring varies for different types of photochemical reaction and different compounds. High pressure imposed on crystals also has a big influence on the free space and the reaction cavity. The wavelength of the applied UV light is another factor which can initiate a reaction and sometimes determine the structure of a product. It is possible, to a certain degree, to control the packing of mol­ecules in stacks by using fluoro substituents on benzene rings. The crystal and mol­ecular structure of 2,6-di­fluoro­cinnamic acid [systematic name: 3-(2,6-di­fluoro­phen­yl)prop-2-enoic acid], C₉H₆F₂O₂, (I), was determined and analysed in terms of a photochemical [2 + 2] dimerization. The mol­ecules are arranged in stacks along the a axis and the values of the inter­molecular geometrical parameters indicate that they may undergo this photochemical reaction. The reaction was carried out in situ and the changes of the unit-cell parameters during crystal irradiation by a UV beam were monitored. The values of the unit-cell parameters change in a different manner, viz. cell length a after an initial increase starts to decrease, b after a decrease starts to increase, c increases and the unit-cell volume V after a certain increase starts to decrease. The structure of a partially reacted crystal, i.e. containing both the reactant and the product, namely 2,6-di­fluoro­cinnamic acid-3,4-bis­(2,6-di­fluoro­phen­yl)cyclo­butane-1,2-di­carb­oxy­lic acid (0.858/0.071), 0.858C₉H₆F₂O₂·0.071C₁₈H₁₂F₄O₄, obtained in situ, is also presented. The powder of compound (I) was irradiated with UV light and afterwards crystallized [as 3,4-bis­(2,6-di­fluoro­phen­yl)cyclo­butane-1,2-di­carb­oxy­lic acid toluene hemisolvate, C₁₈H₁₂F₄O₄·0.5C₇H₈] in a space group different from that of the crystal containing the in-situ dimer.

Computing details

For all compounds, data collection: CrysAlis PRO (Agilent, 2014); cell refinement: CrysAlis PRO (Agilent, 2014); data reduction: CrysAlis PRO (Agilent, 2014); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012), and Mercury (Macrae et al., 2006) and CrystalExplorer (Wolff et al., 2012); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015).

(I) 3-(2,6-Difluorophenyl)prop-2-enoic acid

Crystal data

C9H6F2O2	F(000) = 376
Mr = 184.14	Dx = 1.486 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.8856 (3) Å	Cell parameters from 1694 reflections
b = 19.2920 (11) Å	θ = 1.9–27.8°
c = 10.9859 (6) Å	µ = 0.13 mm^−1
β = 92.221 (6)°	T = 299 K
V = 822.90 (9) Å^3	Block, colourless
Z = 4	0.40 × 0.10 × 0.10 mm

Data collection

KM-4 with an Eos CCD diffractometer	1619 independent reflections
Radiation source: fine-focus sealed tube	1000 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
Detector resolution: 15.9718 pixels mm^-1	θmax = 26.0°, θmin = 2.1°
ω scans	h = −4→4
Absorption correction: multi-scan (Scale3 AbsPack; Agilent, 2014)	k = −23→23
Tmin = 0.941, Tmax = 1.000	l = −11→13
5660 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)] = 0.041	Hydrogen site location: difference Fourier map
wR(F^2) = 0.097	All H-atom parameters refined
S = 1.01	w = 1/[σ^2(Fo^2) + (0.0452P)^2 + 0.0206P] where P = (Fo^2 + 2Fc^2)/3
1619 reflections	(Δ/σ)max < 0.001
142 parameters	Δρmax = 0.12 e Å^−3
0 restraints	Δρmin = −0.16 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

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

	x	y	z	Uiso*/Ueq
C1	0.6089 (5)	0.68850 (11)	0.31454 (17)	0.0548 (5)
C2	0.5472 (6)	0.62027 (13)	0.2868 (2)	0.0684 (6)
C3	0.6458 (6)	0.57058 (13)	0.3707 (2)	0.0734 (6)
C4	0.8057 (6)	0.58904 (12)	0.4791 (2)	0.0662 (6)
C5	0.8668 (5)	0.65801 (10)	0.50136 (18)	0.0542 (5)
C6	0.7719 (4)	0.71153 (9)	0.42229 (16)	0.0476 (4)
C7	0.8488 (5)	0.78374 (10)	0.45376 (18)	0.0519 (5)
C8	0.7703 (5)	0.84073 (10)	0.3921 (2)	0.0595 (5)
C9	0.8729 (5)	0.90905 (10)	0.43898 (19)	0.0585 (5)
F1	0.5022 (3)	0.73662 (6)	0.23180 (10)	0.0817 (4)
F2	1.0335 (3)	0.67519 (6)	0.60770 (10)	0.0760 (4)
O1	0.7799 (4)	0.96057 (9)	0.36678 (15)	0.0892 (5)
O2	1.0322 (4)	0.91805 (7)	0.53550 (13)	0.0760 (5)
H2	0.439 (5)	0.6110 (11)	0.2145 (18)	0.072 (6)*
H3	0.604 (5)	0.5232 (12)	0.3511 (18)	0.077 (6)*
H4	0.871 (6)	0.5584 (12)	0.539 (2)	0.087 (7)*
HO1	0.850 (7)	1.0020 (16)	0.404 (2)	0.132 (11)*
H7	0.971 (4)	0.7885 (10)	0.5286 (16)	0.060 (5)*
H8	0.640 (5)	0.8396 (10)	0.3154 (19)	0.071 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0546 (11)	0.0548 (13)	0.0547 (12)	−0.0012 (9)	−0.0037 (9)	0.0027 (10)
C2	0.0678 (14)	0.0645 (16)	0.0719 (15)	−0.0113 (11)	−0.0088 (12)	−0.0160 (13)
C3	0.0760 (15)	0.0474 (14)	0.0964 (18)	−0.0068 (11)	−0.0017 (13)	−0.0104 (14)
C4	0.0726 (14)	0.0461 (13)	0.0796 (16)	0.0021 (11)	−0.0005 (12)	0.0029 (12)
C5	0.0565 (11)	0.0503 (12)	0.0555 (11)	0.0027 (9)	−0.0012 (9)	−0.0048 (10)
C6	0.0470 (10)	0.0439 (11)	0.0519 (11)	−0.0012 (8)	0.0031 (8)	−0.0011 (9)
C7	0.0580 (11)	0.0469 (12)	0.0502 (11)	0.0000 (9)	−0.0035 (9)	−0.0013 (10)
C8	0.0712 (13)	0.0505 (13)	0.0560 (13)	−0.0003 (10)	−0.0082 (10)	0.0019 (10)
C9	0.0715 (13)	0.0445 (12)	0.0588 (12)	0.0043 (10)	−0.0086 (10)	0.0054 (11)
F1	0.1053 (9)	0.0715 (9)	0.0661 (8)	−0.0070 (7)	−0.0265 (7)	0.0066 (6)
F2	0.1042 (9)	0.0599 (8)	0.0620 (7)	0.0062 (6)	−0.0197 (6)	0.0028 (6)
O1	0.1365 (14)	0.0463 (9)	0.0812 (10)	−0.0014 (9)	−0.0421 (9)	0.0111 (8)
O2	0.1111 (12)	0.0435 (9)	0.0708 (10)	−0.0005 (7)	−0.0305 (9)	0.0054 (7)

Geometric parameters (Å, º)

C1—F1	1.353 (2)	C5—C6	1.390 (2)
C1—C2	1.370 (3)	C6—C7	1.463 (2)
C1—C6	1.393 (2)	C7—C8	1.321 (3)
C2—C3	1.374 (3)	C7—H7	0.938 (18)
C2—H2	0.90 (2)	C8—C9	1.465 (3)
C3—C4	1.370 (3)	C8—H8	0.97 (2)
C3—H3	0.95 (2)	C9—O2	1.219 (2)
C4—C5	1.372 (3)	C9—O1	1.313 (2)
C4—H4	0.91 (2)	O1—HO1	0.93 (3)
C5—F2	1.355 (2)
F1—C1—C2	117.59 (18)	C4—C5—C6	124.71 (19)
F1—C1—C6	117.99 (17)	C5—C6—C1	113.26 (16)
C2—C1—C6	124.4 (2)	C5—C6—C7	120.84 (16)
C1—C2—C3	118.6 (2)	C1—C6—C7	125.89 (17)
C1—C2—H2	117.2 (14)	C8—C7—C6	129.07 (19)
C3—C2—H2	124.2 (14)	C8—C7—H7	117.8 (12)
C4—C3—C2	120.5 (2)	C6—C7—H7	113.1 (12)
C4—C3—H3	121.0 (13)	C7—C8—C9	120.98 (19)
C2—C3—H3	118.5 (13)	C7—C8—H8	122.1 (12)
C3—C4—C5	118.5 (2)	C9—C8—H8	116.9 (12)
C3—C4—H4	124.1 (14)	O2—C9—O1	122.40 (18)
C5—C4—H4	117.4 (14)	O2—C9—C8	123.76 (19)
F2—C5—C4	117.67 (19)	O1—C9—C8	113.83 (19)
F2—C5—C6	117.62 (16)	C9—O1—HO1	108.6 (17)

(II) 2,6-Difluorocinnamic acid–3,4-bis(2,6-difluorophenyl)cyclobutane-1,2-dicarboxylic acid (0.858/0.071)

Crystal data

0.858C9H6F2O2·0.071C18H12F4O4	F(000) = 376
Mr = 184.14	Dx = 1.472 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.8860 (6) Å	Cell parameters from 517 reflections
b = 19.185 (4) Å	θ = 3.6–23.3°
c = 11.1567 (14) Å	µ = 0.13 mm^−1
β = 92.873 (14)°	T = 299 K
V = 830.7 (2) Å^3	Block, colourless
Z = 4	0.62 × 0.25 × 0.12 mm

Data collection

KM-4 with an Eos CCD diffractometer	1413 independent reflections
Radiation source: fine-focus sealed tube	772 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
Detector resolution: 15.9718 pixels mm^-1	θmax = 25.0°, θmin = 2.1°
ω scans	h = −4→4
Absorption correction: multi-scan (Scale3 AbsPack; Agilent, 2014)	k = −22→21
Tmin = 0.493, Tmax = 1.000	l = −13→12
2470 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)] = 0.074	Hydrogen site location: mixed
wR(F^2) = 0.233	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.1209P)^2 + 0.0466P] where P = (Fo^2 + 2Fc^2)/3
1413 reflections	(Δ/σ)max = 0.001
182 parameters	Δρmax = 0.18 e Å^−3
199 restraints	Δρmin = −0.16 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1R	0.8933 (14)	0.6885 (4)	1.1851 (5)	0.0834 (19)	0.858 (6)
F1R	0.9970 (12)	0.7368 (2)	1.2676 (3)	0.1150 (17)	0.858 (6)
C2R	0.9568 (14)	0.6202 (4)	1.2141 (5)	0.0933 (17)	0.858 (6)
H2R	1.0638	0.6083	1.2877	0.112*	0.858 (6)
C3R	0.8591 (15)	0.5698 (3)	1.1322 (6)	0.1034 (19)	0.858 (6)
H3R	0.8976	0.5231	1.1507	0.124*	0.858 (6)
C4R	0.704 (2)	0.5878 (4)	1.0225 (7)	0.103 (2)	0.858 (6)
H4R	0.6430	0.5539	0.9657	0.124*	0.858 (6)
C5R	0.6412 (16)	0.6574 (3)	0.9994 (5)	0.0818 (19)	0.858 (6)
F2R	0.4783 (13)	0.67466 (19)	0.8954 (3)	0.0999 (15)	0.858 (6)
C6R	0.7329 (13)	0.7109 (3)	1.0796 (4)	0.0710 (13)	0.858 (6)
C7R	0.6549 (11)	0.7832 (3)	1.0466 (4)	0.0770 (14)	0.858 (6)
H7R	0.5404	0.7894	0.9722	0.092*	0.858 (6)
C8R	0.7247 (12)	0.8410 (3)	1.1080 (4)	0.0881 (15)	0.858 (6)
H8R	0.8429	0.8381	1.1825	0.106*	0.858 (6)
C9R	0.6193 (15)	0.9093 (3)	1.0609 (4)	0.0825 (15)	0.858 (6)
O1R	0.7174 (18)	0.9610 (3)	1.1324 (5)	0.1173 (19)	0.858 (6)
H2R1	0.6798	0.9982	1.0980	0.176*	0.858 (6)
O2R	0.471 (2)	0.9177 (3)	0.9656 (3)	0.1047 (18)	0.858 (6)
C6P1	0.871 (7)	0.7041 (14)	1.077 (3)	0.069 (16)*	0.071 (3)
C1P1	0.928 (11)	0.681 (2)	1.194 (3)	0.09 (2)*	0.071 (3)
F1P1	1.075 (14)	0.726 (3)	1.275 (3)	0.123 (18)*	0.071 (3)
C2P1	0.844 (15)	0.616 (2)	1.233 (3)	0.11 (2)*	0.071 (3)
H2P1	0.9056	0.6073	1.3154	0.130*	0.071 (3)
C3P1	0.690 (16)	0.570 (2)	1.153 (4)	0.119 (18)*	0.071 (3)
H3P1	0.6334	0.5229	1.1818	0.143*	0.071 (3)
C4P1	0.625 (13)	0.5892 (16)	1.035 (4)	0.093 (19)*	0.071 (3)
H4P1	0.5231	0.5603	0.9785	0.112*	0.071 (3)
C5P1	0.718 (7)	0.6548 (14)	1.000 (3)	0.10 (2)*	0.071 (3)
F2P1	0.659 (9)	0.673 (2)	0.884 (3)	0.089 (13)*	0.071 (3)
C7P1	0.976 (7)	0.7760 (14)	1.036 (3)	0.075 (5)*	0.071 (3)
H7P1	0.8718	0.7869	0.9559	0.090*	0.071 (3)
C8P1	0.938 (8)	0.8381 (15)	1.124 (3)	0.085 (5)*	0.071 (3)
H8P1	0.8661	0.8239	1.2033	0.102*	0.071 (3)
C9P1	0.731 (9)	0.8981 (18)	1.071 (4)	0.084 (10)*	0.071 (3)
O1P1	0.625 (15)	0.942 (2)	1.150 (5)	0.093 (16)*	0.071 (3)
H1P1	0.4740	0.9720	1.1100	0.111*	0.071 (3)
O2P1	0.662 (15)	0.903 (3)	0.964 (4)	0.126 (16)*	0.071 (3)
C6P2	1.600 (7)	0.7241 (15)	1.074 (3)	0.081 (17)*	0.071 (3)
C1P2	1.829 (8)	0.7184 (19)	1.173 (3)	0.095 (17)*	0.071 (3)
F1P2	1.885 (10)	0.777 (2)	1.238 (3)	0.146 (14)*	0.071 (3)
C2P2	2.006 (12)	0.659 (2)	1.205 (4)	0.110 (19)*	0.071 (3)
H2P2	2.1531	0.6584	1.2702	0.131*	0.071 (3)
C3P2	1.957 (15)	0.601 (2)	1.135 (6)	0.127 (19)*	0.071 (3)
H3P2	2.0769	0.5565	1.1524	0.152*	0.071 (3)
C4P2	1.741 (14)	0.6030 (16)	1.035 (5)	0.094 (19)*	0.071 (3)
H4P2	1.6908	0.5652	0.9809	0.112*	0.071 (3)
C5P2	1.567 (10)	0.6640 (17)	1.006 (3)	0.09 (2)*	0.071 (3)
F2P2	1.355 (12)	0.665 (3)	0.906 (4)	0.103 (16)*	0.071 (3)
C7P2	1.382 (7)	0.7866 (14)	1.040 (3)	0.077 (5)*	0.071 (3)
H7P2	1.4465	0.8026	0.9607	0.092*	0.071 (3)
C8P2	1.340 (8)	0.8506 (15)	1.119 (3)	0.085 (5)*	0.071 (3)
H8P2	1.4579	0.8449	1.1985	0.101*	0.071 (3)
C9P2	1.423 (11)	0.9188 (17)	1.063 (3)	0.088 (10)*	0.071 (3)
O1P2	1.470 (13)	0.9677 (19)	1.144 (4)	0.099 (12)*	0.071 (3)
H1P2	1.5598	1.0008	1.1122	0.119*	0.071 (3)
O2P2	1.45 (3)	0.928 (3)	0.956 (3)	0.120 (19)*	0.071 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1R	0.068 (3)	0.087 (4)	0.094 (4)	0.007 (3)	−0.006 (2)	0.001 (3)
F1R	0.147 (4)	0.100 (3)	0.094 (2)	0.005 (3)	−0.0340 (19)	−0.0062 (17)
C2R	0.086 (4)	0.091 (5)	0.101 (3)	0.014 (3)	−0.010 (3)	0.013 (3)
C3R	0.087 (4)	0.084 (4)	0.138 (5)	0.010 (3)	−0.001 (3)	0.016 (4)
C4R	0.105 (5)	0.069 (4)	0.135 (5)	−0.003 (3)	−0.003 (4)	−0.007 (3)
C5R	0.078 (3)	0.081 (4)	0.086 (3)	−0.002 (3)	0.003 (2)	0.005 (3)
F2R	0.122 (4)	0.084 (3)	0.091 (2)	−0.008 (2)	−0.018 (2)	−0.0044 (15)
C6R	0.060 (3)	0.072 (4)	0.081 (3)	0.007 (2)	0.004 (2)	0.002 (2)
C7R	0.078 (3)	0.079 (3)	0.074 (2)	−0.003 (2)	−0.0049 (19)	0.003 (2)
C8R	0.096 (3)	0.087 (4)	0.079 (2)	0.002 (3)	−0.014 (2)	−0.004 (2)
C9R	0.097 (4)	0.071 (3)	0.078 (3)	0.005 (3)	−0.011 (3)	−0.002 (2)
O1R	0.166 (5)	0.074 (3)	0.107 (3)	−0.009 (3)	−0.043 (3)	−0.016 (2)
O2R	0.144 (4)	0.070 (3)	0.096 (3)	−0.001 (3)	−0.036 (2)	−0.0070 (17)

Geometric parameters (Å, º)

C1R—F1R	1.354 (6)	C5P1—F2P1	1.3553
C1R—C2R	1.369 (9)	C7P1—C8P1	1.559 (19)
C1R—C6R	1.373 (7)	C7P1—C7P2	1.590 (19)
C2R—C3R	1.371 (8)	C7P1—H7P1	0.9800
C2R—H2R	0.9300	C8P1—C9P1	1.510 (17)
C3R—C4R	1.381 (8)	C8P1—C8P2	1.582 (19)
C3R—H3R	0.9300	C8P1—H8P1	0.9800
C4R—C5R	1.379 (8)	C9P1—O2P1	1.2133
C4R—H4R	0.9300	C9P1—O1P1	1.3057
C5R—F2R	1.335 (5)	O1P1—H1P1	0.9135
C5R—C6R	1.396 (7)	C6P2—C5P2	1.3794
C6R—C7R	1.463 (7)	C6P2—C1P2	1.3863
C7R—C8R	1.324 (6)	C6P2—C7P2	1.504 (17)
C7R—H7R	0.9300	C1P2—F1P2	1.3550
C8R—C9R	1.463 (7)	C1P2—C2P2	1.3757
C8R—H8R	0.9300	C2P2—C3P2	1.3675
C9R—O2R	1.195 (7)	C2P2—H2P2	0.9029
C9R—O1R	1.318 (6)	C3P2—C4P2	1.3665
O1R—H2R1	0.8200	C3P2—H3P2	0.9808
C6P1—C5P1	1.3863	C4P2—C5P2	1.3804
C6P1—C1P1	1.3878	C4P2—H4P2	0.9538
C6P1—C7P1	1.517 (17)	C5P2—F2P2	1.3562
C1P1—F1P1	1.3510	C7P2—C8P2	1.530 (19)
C1P1—C2P1	1.3768	C7P2—H7P2	0.9800
C2P1—C3P1	1.3720 (11)	C8P2—C9P2	1.492 (17)
C2P1—H2P1	0.9480	C8P2—H8P2	0.9800
C3P1—C4P1	1.3731	C9P2—O2P2	1.2184
C3P1—H3P1	0.9851	C9P2—O1P2	1.3039
C4P1—C5P1	1.3711	O1P2—H1P2	0.8117
C4P1—H4P1	0.9182
F1R—C1R—C2R	116.8 (5)	C8P1—C7P1—C7P2	90.5 (15)
F1R—C1R—C6R	118.4 (6)	C6P1—C7P1—H7P1	111.3
C2R—C1R—C6R	124.8 (5)	C8P1—C7P1—H7P1	111.3
C1R—C2R—C3R	118.5 (5)	C7P2—C7P1—H7P1	111.3
C1R—C2R—H2R	120.8	C9P1—C8P1—C7P1	113 (2)
C3R—C2R—H2R	120.8	C9P1—C8P1—C8P2	112 (2)
C2R—C3R—C4R	120.6 (6)	C7P1—C8P1—C8P2	88.4 (15)
C2R—C3R—H3R	119.7	C9P1—C8P1—H8P1	113.5
C4R—C3R—H3R	119.7	C7P1—C8P1—H8P1	113.5
C5R—C4R—C3R	118.2 (6)	C8P2—C8P1—H8P1	113.5
C5R—C4R—H4R	120.9	O2P1—C9P1—O1P1	123.5
C3R—C4R—H4R	120.9	O2P1—C9P1—C8P1	122 (2)
F2R—C5R—C4R	118.3 (5)	O1P1—C9P1—C8P1	114 (2)
F2R—C5R—C6R	118.0 (5)	C9P1—O1P1—H1P1	107.2
C4R—C5R—C6R	123.7 (5)	C5P2—C6P2—C1P2	113.9
C1R—C6R—C5R	114.2 (5)	C5P2—C6P2—C7P2	119.5 (17)
C1R—C6R—C7R	126.3 (5)	C1P2—C6P2—C7P2	126.4 (17)
C5R—C6R—C7R	119.5 (4)	F1P2—C1P2—C2P2	119.19 (6)
C8R—C7R—C6R	129.0 (4)	F1P2—C1P2—C6P2	116.2
C8R—C7R—H7R	115.5	C2P2—C1P2—C6P2	124.6
C6R—C7R—H7R	115.5	C3P2—C2P2—C1P2	118.36 (6)
C7R—C8R—C9R	121.1 (4)	C3P2—C2P2—H2P2	121.4
C7R—C8R—H8R	119.4	C1P2—C2P2—H2P2	120.3
C9R—C8R—H8R	119.4	C4P2—C3P2—C2P2	120.2
O2R—C9R—O1R	123.2 (5)	C4P2—C3P2—H3P2	117.3
O2R—C9R—C8R	123.8 (5)	C2P2—C3P2—H3P2	122.5
O1R—C9R—C8R	112.9 (5)	C3P2—C4P2—C5P2	119.2
C9R—O1R—H2R1	109.5	C3P2—C4P2—H4P2	125.9
C5P1—C6P1—C1P1	114.0	C5P2—C4P2—H4P2	114.8
C5P1—C6P1—C7P1	123.2 (16)	F2P2—C5P2—C6P2	118.5
C1P1—C6P1—C7P1	122.7 (16)	F2P2—C5P2—C4P2	117.8
F1P1—C1P1—C2P1	117.8	C6P2—C5P2—C4P2	123.66 (6)
F1P1—C1P1—C6P1	118.06 (6)	C6P2—C7P2—C8P2	125 (2)
C2P1—C1P1—C6P1	124.11 (6)	C6P2—C7P2—C7P1	116.9 (19)
C3P1—C2P1—C1P1	118.6	C8P2—C7P2—C7P1	89.1 (15)
C3P1—C2P1—H2P1	127.2	C6P2—C7P2—H7P2	108.1
C1P1—C2P1—H2P1	114.2	C8P2—C7P2—H7P2	108.1
C2P1—C3P1—C4P1	120.32 (8)	C7P1—C7P2—H7P2	108.1
C2P1—C3P1—H3P1	117.8	C9P2—C8P2—C7P2	115 (2)
C4P1—C3P1—H3P1	121.9	C9P2—C8P2—C8P1	113 (2)
C5P1—C4P1—C3P1	118.82 (8)	C7P2—C8P2—C8P1	91.8 (15)
C5P1—C4P1—H4P1	118.0	C9P2—C8P2—H8P2	111.9
C3P1—C4P1—H4P1	123.2	C7P2—C8P2—H8P2	111.9
F2P1—C5P1—C4P1	118.17 (7)	C8P1—C8P2—H8P2	111.9
F2P1—C5P1—C6P1	117.7	O2P2—C9P2—O1P2	123.35 (9)
C4P1—C5P1—C6P1	124.2	O2P2—C9P2—C8P2	125 (2)
C6P1—C7P1—C8P1	118 (2)	O1P2—C9P2—C8P2	112 (2)
C6P1—C7P1—C7P2	112.8 (18)	C9P2—O1P2—H1P2	108.4

(III) 3,4-Bis(2,6-difluorophenyl)cyclobutane-1,2-dicarboxylic acid toluene hemisolvate

Crystal data

C18H12F4O4·0.5C7H8	Z = 2
Mr = 414.34	F(000) = 426
Triclinic, P1	Dx = 1.473 Mg m^−3
a = 7.6212 (5) Å	Mo Kα radiation, λ = 0.71073 Å
b = 10.3137 (10) Å	Cell parameters from 2280 reflections
c = 13.1849 (10) Å	θ = 2.2–26.8°
α = 112.145 (8)°	µ = 0.13 mm^−1
β = 96.843 (6)°	T = 299 K
γ = 97.960 (7)°	Block, colourless
V = 933.94 (14) Å^3	0.42 × 0.38 × 0.25 mm

Data collection

KM-4 with an Eos CCD diffractometer	3661 independent reflections
Radiation source: fine-focus sealed tube	2747 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
Detector resolution: 15.9718 pixels mm^-1	θmax = 26.0°, θmin = 2.2°
ω scans	h = −9→9
Absorption correction: multi-scan (Scale3 AbsPack; Agilent, 2014)	k = −12→12
Tmin = 0.999, Tmax = 1.000	l = −16→15
6370 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)] = 0.048	Hydrogen site location: mixed
wR(F^2) = 0.127	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ^2(Fo^2) + (0.059P)^2 + 0.2977P] where P = (Fo^2 + 2Fc^2)/3
3661 reflections	(Δ/σ)max < 0.001
347 parameters	Δρmax = 0.36 e Å^−3
49 restraints	Δρmin = −0.18 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1	0.4304 (3)	0.4154 (2)	0.16562 (17)	0.0410 (5)
C2	0.3003 (3)	0.4967 (3)	0.1772 (2)	0.0547 (6)
C3	0.3394 (4)	0.6275 (3)	0.1716 (2)	0.0605 (7)
C4	0.5055 (4)	0.6752 (3)	0.1541 (2)	0.0566 (6)
C5	0.6305 (3)	0.5885 (2)	0.14126 (18)	0.0435 (5)
C6	0.6003 (3)	0.4554 (2)	0.14628 (15)	0.0355 (4)
C7	0.7432 (3)	0.3663 (2)	0.13256 (16)	0.0352 (4)
C8	0.6845 (3)	0.2040 (2)	0.05624 (17)	0.0365 (4)
C9	0.8035 (3)	0.1506 (2)	−0.02623 (17)	0.0391 (5)
C10	0.6987 (3)	0.3518 (3)	0.41310 (19)	0.0507 (5)
C11	0.6834 (3)	0.4328 (4)	0.5210 (2)	0.0623 (7)
C12	0.7511 (3)	0.5765 (3)	0.5657 (2)	0.0632 (7)
C13	0.8365 (4)	0.6384 (3)	0.5049 (2)	0.0612 (7)
C14	0.8496 (3)	0.5530 (2)	0.39804 (18)	0.0478 (5)
C15	0.7809 (3)	0.4073 (2)	0.34653 (16)	0.0393 (5)
C16	0.8157 (3)	0.3271 (2)	0.23208 (16)	0.0355 (4)
C17	0.7307 (3)	0.1690 (2)	0.16231 (16)	0.0358 (4)
C18	0.8528 (3)	0.0648 (2)	0.15314 (17)	0.0387 (4)
F1	0.39116 (16)	0.28763 (13)	0.17349 (12)	0.0568 (4)
F2	0.79258 (19)	0.63608 (14)	0.12238 (13)	0.0638 (4)
F3	0.6311 (2)	0.20932 (17)	0.37129 (13)	0.0812 (5)
F4	0.9399 (2)	0.61154 (14)	0.33808 (12)	0.0654 (4)
O1	0.7241 (2)	0.03875 (19)	−0.11596 (14)	0.0642 (5)
O2	0.9622 (2)	0.20440 (17)	−0.00828 (15)	0.0607 (5)
O3	0.7766 (2)	−0.06603 (16)	0.08604 (15)	0.0565 (5)
O4	1.0097 (2)	0.09963 (17)	0.20065 (14)	0.0575 (4)
H2	0.191 (4)	0.461 (3)	0.189 (2)	0.063 (7)*
H3	0.252 (4)	0.691 (3)	0.181 (2)	0.083 (9)*
H4	0.547 (4)	0.764 (3)	0.151 (2)	0.073 (8)*
H7	0.838 (3)	0.413 (2)	0.1097 (16)	0.030 (5)*
H8	0.560 (3)	0.167 (2)	0.0193 (17)	0.038 (5)*
HO1	0.812 (5)	0.005 (4)	−0.154 (3)	0.097 (11)*
H11	0.622 (4)	0.381 (3)	0.557 (2)	0.073 (8)*
H12	0.738 (4)	0.631 (3)	0.642 (3)	0.078 (8)*
H13	0.885 (4)	0.733 (4)	0.534 (3)	0.083 (10)*
H16	0.943 (3)	0.333 (2)	0.2351 (16)	0.031 (5)*
H17	0.629 (3)	0.136 (2)	0.1828 (17)	0.040 (5)*
HO2	0.855 (5)	−0.112 (4)	0.071 (3)	0.119 (14)*
C19	0.901 (2)	0.9424 (15)	0.4049 (12)	0.129 (4)	0.5
H19	0.8878	0.9004	0.3277	0.155*	0.5
C20	0.7509 (15)	0.9655 (12)	0.4532 (11)	0.146 (4)	0.5
H20	0.6364	0.9403	0.4095	0.175*	0.5
C21	0.7744 (19)	1.0250 (14)	0.5644 (12)	0.162 (4)	0.5
H21	0.6734	1.0372	0.5976	0.195*	0.5
C22	0.9382 (19)	1.0678 (9)	0.6301 (8)	0.125 (3)	0.5
H22	0.9481	1.1154	0.7067	0.150*	0.5
C23	1.094 (2)	1.0423 (17)	0.5860 (11)	0.125 (4)	0.5
H23	1.2062	1.0652	0.6318	0.150*	0.5
C24	1.0733 (17)	0.9811 (10)	0.4705 (11)	0.146 (3)	0.5
C25	1.232 (2)	0.953 (2)	0.4169 (16)	0.210 (7)	0.5
H25A	1.2655	0.8680	0.4202	0.315*	0.5
H25B	1.3311	1.0324	0.4552	0.315*	0.5
H25C	1.2028	0.9400	0.3404	0.315*	0.5

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0443 (11)	0.0377 (11)	0.0433 (11)	0.0122 (9)	0.0117 (9)	0.0162 (9)
C2	0.0457 (13)	0.0631 (16)	0.0611 (15)	0.0222 (11)	0.0168 (11)	0.0255 (12)
C3	0.0665 (16)	0.0615 (16)	0.0642 (16)	0.0364 (13)	0.0150 (12)	0.0279 (13)
C4	0.0754 (17)	0.0468 (14)	0.0572 (15)	0.0244 (12)	0.0116 (12)	0.0274 (12)
C5	0.0507 (12)	0.0407 (11)	0.0424 (11)	0.0098 (9)	0.0106 (9)	0.0193 (9)
C6	0.0407 (10)	0.0340 (10)	0.0314 (10)	0.0108 (8)	0.0074 (8)	0.0114 (8)
C7	0.0346 (10)	0.0323 (10)	0.0400 (11)	0.0075 (8)	0.0114 (8)	0.0143 (8)
C8	0.0332 (10)	0.0339 (10)	0.0384 (11)	0.0077 (8)	0.0064 (8)	0.0100 (8)
C9	0.0444 (11)	0.0339 (10)	0.0403 (11)	0.0130 (9)	0.0087 (9)	0.0144 (9)
C10	0.0487 (12)	0.0538 (14)	0.0486 (13)	0.0109 (10)	0.0098 (10)	0.0189 (11)
C11	0.0514 (14)	0.094 (2)	0.0441 (14)	0.0211 (14)	0.0121 (11)	0.0269 (14)
C12	0.0554 (14)	0.084 (2)	0.0386 (13)	0.0301 (14)	0.0047 (11)	0.0071 (13)
C13	0.0649 (16)	0.0531 (16)	0.0489 (14)	0.0229 (13)	−0.0040 (12)	0.0026 (12)
C14	0.0471 (12)	0.0462 (13)	0.0457 (12)	0.0127 (10)	0.0009 (9)	0.0148 (10)
C15	0.0352 (10)	0.0421 (11)	0.0387 (11)	0.0152 (8)	0.0036 (8)	0.0123 (9)
C16	0.0319 (10)	0.0334 (10)	0.0415 (11)	0.0093 (8)	0.0088 (8)	0.0138 (8)
C17	0.0327 (10)	0.0327 (10)	0.0418 (11)	0.0070 (8)	0.0121 (8)	0.0129 (8)
C18	0.0427 (11)	0.0358 (11)	0.0412 (11)	0.0103 (8)	0.0134 (9)	0.0168 (9)
F1	0.0497 (7)	0.0468 (7)	0.0838 (10)	0.0123 (6)	0.0285 (7)	0.0315 (7)
F2	0.0669 (9)	0.0516 (8)	0.0859 (10)	0.0077 (7)	0.0276 (7)	0.0391 (8)
F3	0.1139 (13)	0.0659 (10)	0.0621 (9)	−0.0049 (9)	0.0268 (9)	0.0287 (8)
F4	0.0823 (10)	0.0421 (7)	0.0600 (9)	−0.0027 (7)	0.0064 (7)	0.0148 (6)
O1	0.0585 (10)	0.0611 (11)	0.0503 (10)	0.0219 (8)	0.0065 (8)	−0.0049 (8)
O2	0.0507 (9)	0.0484 (9)	0.0733 (11)	0.0083 (7)	0.0292 (8)	0.0091 (8)
O3	0.0478 (9)	0.0323 (8)	0.0811 (12)	0.0110 (7)	0.0139 (8)	0.0121 (8)
O4	0.0492 (9)	0.0521 (9)	0.0594 (10)	0.0216 (7)	−0.0003 (7)	0.0086 (8)
C19	0.200 (8)	0.074 (6)	0.098 (6)	0.024 (6)	−0.004 (7)	0.028 (5)
C20	0.151 (9)	0.125 (8)	0.161 (11)	0.049 (7)	0.008 (8)	0.056 (8)
C21	0.206 (10)	0.093 (6)	0.226 (11)	0.070 (7)	0.107 (8)	0.073 (7)
C22	0.190 (10)	0.075 (5)	0.122 (8)	0.027 (7)	0.031 (8)	0.051 (5)
C23	0.201 (8)	0.068 (5)	0.095 (6)	0.017 (6)	−0.003 (7)	0.032 (5)
C24	0.217 (11)	0.078 (5)	0.195 (10)	0.057 (6)	0.107 (7)	0.083 (6)
C25	0.235 (12)	0.134 (10)	0.266 (13)	0.041 (10)	0.093 (11)	0.071 (10)

Geometric parameters (Å, º)

C1—F1	1.355 (2)	C15—C16	1.499 (3)
C1—C2	1.371 (3)	C16—C17	1.536 (3)
C1—C6	1.386 (3)	C16—H16	0.96 (2)
C2—C3	1.373 (4)	C17—C18	1.497 (3)
C2—H2	0.92 (3)	C17—H17	0.91 (2)
C3—C4	1.372 (4)	C18—O4	1.218 (2)
C3—H3	0.99 (3)	C18—O3	1.304 (3)
C4—C5	1.377 (3)	O1—HO1	0.91 (4)
C4—H4	0.95 (3)	O3—HO2	0.81 (4)
C5—F2	1.351 (2)	C19—C20	1.383 (9)
C5—C6	1.388 (3)	C19—C24	1.396 (9)
C6—C7	1.504 (3)	C19—H19	0.9300
C7—C8	1.559 (3)	C20—C21	1.336 (9)
C7—C16	1.574 (3)	C20—H20	0.9300
C7—H7	0.95 (2)	C21—C22	1.343 (9)
C8—C9	1.493 (3)	C21—H21	0.9300
C8—C17	1.584 (3)	C22—C23	1.398 (9)
C8—H8	0.96 (2)	C22—H22	0.9300
C9—O2	1.213 (2)	C23—C24	1.391 (9)
C9—O1	1.306 (3)	C23—H23	0.9300
C10—F3	1.356 (3)	C24—C22^i	1.215 (16)
C10—C15	1.379 (3)	C24—C21^i	1.30 (2)
C10—C11	1.380 (3)	C24—C23^i	1.34 (3)
C11—C12	1.367 (4)	C24—C24^i	1.45 (2)
C11—H11	0.95 (3)	C24—C20^i	1.47 (2)
C12—C13	1.367 (4)	C24—C25	1.482 (9)
C12—H12	0.98 (3)	C24—C19^i	1.50 (2)
C13—C14	1.376 (3)	C25—H25A	0.9600
C13—H13	0.90 (3)	C25—H25B	0.9600
C14—F4	1.355 (3)	C25—H25C	0.9600
C14—C15	1.386 (3)
F1—C1—C2	118.18 (19)	O4—C18—O3	123.34 (19)
F1—C1—C6	117.67 (17)	O4—C18—C17	123.23 (18)
C2—C1—C6	124.2 (2)	O3—C18—C17	113.37 (18)
C1—C2—C3	118.8 (2)	C9—O1—HO1	107 (2)
C1—C2—H2	118.0 (17)	C18—O3—HO2	108 (3)
C3—C2—H2	123.2 (17)	C20—C19—C24	120.9 (10)
C4—C3—C2	120.3 (2)	C20—C19—H19	119.5
C4—C3—H3	117.8 (17)	C24—C19—H19	119.5
C2—C3—H3	121.9 (18)	C21—C20—C19	118.2 (11)
C3—C4—C5	118.6 (2)	C21—C20—H20	120.9
C3—C4—H4	127.2 (17)	C19—C20—H20	120.9
C5—C4—H4	114.2 (17)	C20—C21—C22	122.6 (10)
F2—C5—C4	117.8 (2)	C20—C21—H21	118.7
F2—C5—C6	118.06 (18)	C22—C21—H21	118.7
C4—C5—C6	124.1 (2)	C21—C22—C23	121.5 (10)
C1—C6—C5	114.00 (18)	C21—C22—H22	119.2
C1—C6—C7	124.46 (17)	C23—C22—H22	119.2
C5—C6—C7	121.53 (18)	C24—C23—C22	116.9 (10)
C6—C7—C8	117.61 (16)	C24—C23—H23	121.6
C6—C7—C16	118.65 (16)	C22—C23—H23	121.6
C8—C7—C16	89.48 (14)	C22^i—C24—C21^i	64.5 (9)
C6—C7—H7	106.0 (12)	C22^i—C24—C23^i	66.2 (11)
C8—C7—H7	112.5 (11)	C21^i—C24—C23^i	130.1 (15)
C16—C7—H7	112.2 (11)	C22^i—C24—C23	177.0 (11)
C9—C8—C7	113.86 (16)	C21^i—C24—C23	113.3 (11)
C9—C8—C17	112.19 (16)	C23^i—C24—C23	115.8 (10)
C7—C8—C17	89.10 (14)	C22^i—C24—C19	62.4 (10)
C9—C8—H8	109.0 (12)	C21^i—C24—C19	126.8 (10)
C7—C8—H8	118.7 (12)	C23^i—C24—C19	6.0 (11)
C17—C8—H8	112.7 (12)	C23—C24—C19	119.7 (8)
O2—C9—O1	123.52 (19)	C22^i—C24—C24^i	125.8 (18)
O2—C9—C8	122.14 (18)	C21^i—C24—C24^i	166.6 (16)
O1—C9—C8	114.28 (18)	C23^i—C24—C24^i	59.7 (9)
F3—C10—C15	118.5 (2)	C23—C24—C24^i	56.1 (11)
F3—C10—C11	117.8 (2)	C19—C24—C24^i	63.8 (12)
C15—C10—C11	123.7 (2)	C22^i—C24—C20^i	121.7 (13)
C12—C11—C10	119.2 (3)	C21^i—C24—C20^i	57.2 (9)
C12—C11—H11	126.0 (18)	C23^i—C24—C20^i	168.4 (13)
C10—C11—H11	114.8 (18)	C23—C24—C20^i	56.0 (8)
C11—C12—C13	120.3 (2)	C19—C24—C20^i	174.4 (8)
C11—C12—H12	117.2 (17)	C24^i—C24—C20^i	111.6 (14)
C13—C12—H12	122.5 (17)	C22^i—C24—C25	57.6 (11)
C12—C13—C14	118.4 (3)	C21^i—C24—C25	8.9 (11)
C12—C13—H13	121 (2)	C23^i—C24—C25	123.8 (13)
C14—C13—H13	120 (2)	C23—C24—C25	120.3 (11)
F4—C14—C13	119.2 (2)	C19—C24—C25	119.9 (10)
F4—C14—C15	116.22 (19)	C24^i—C24—C25	175.5 (15)
C13—C14—C15	124.6 (2)	C20^i—C24—C25	64.6 (10)
C10—C15—C14	113.9 (2)	C22^i—C24—C19^i	173.3 (12)
C10—C15—C16	127.55 (19)	C21^i—C24—C19^i	112.4 (15)
C14—C15—C16	118.30 (19)	C23^i—C24—C19^i	115.8 (12)
C15—C16—C17	122.86 (17)	C23—C24—C19^i	4.1 (12)
C15—C16—C7	120.12 (16)	C19—C24—C19^i	120.1 (10)
C17—C16—C7	90.26 (14)	C24^i—C24—C19^i	56.3 (7)
C15—C16—H16	109.3 (12)	C20^i—C24—C19^i	55.4 (8)
C17—C16—H16	105.3 (11)	C25—C24—C19^i	119.9 (14)
C7—C16—H16	106.6 (12)	C24—C25—H25A	109.5
C18—C17—C16	116.38 (16)	C24—C25—H25B	109.5
C18—C17—C8	116.18 (16)	H25A—C25—H25B	109.5
C16—C17—C8	89.94 (15)	C24—C25—H25C	109.5
C18—C17—H17	107.1 (13)	H25A—C25—H25C	109.5
C16—C17—H17	114.8 (13)	H25B—C25—H25C	109.5
C8—C17—H17	112.0 (13)

Symmetry code: (i) −x+2, −y+2, −z+1.