Buy article online - an online subscription or single-article purchase is required to access this article.
The title compound, C23H22F6O4S2, a photochromic dithienylethene, is a promising material for optical storage and other optoelectrical devices. The molecule adopts a photoactive antiparallel conformation in the crystalline state. The distance between the two reactive C atoms which are involved in potential ring closure is 3.829 (4) Å. The dihedral angles between the central cyclopentene ring and the adjacent thiophene rings are 55.38 (7) and 54.81 (9)°. The colourless crystals turn magenta when exposed to UV radiation and the process is reversible.
Supporting information
CCDC reference: 285804
The title diarylethene (Ia) was originally derived from 5-ethylthiophene-2-carbaldehyde, (1). First, 4-bromo-5-ethylthiophene-2-carbaldehyde, (2), was afforded in 73.3% yield by brominating compound (1) in acetic acid at room temperature. The dioxolane acetal, (3), was then prepared in 84.0% yield by refluxing under Dean–Stark conditions in the presence of compound (2), glycol and p-toluenesulfonic acid (TsOH) in benzene. Finally, to a stirred solution of compound (3) (2.296 g, 8.73 mmol) in tetrahydrofuran (50 ml) was added dropwise a 2.5 M n-BuLi Solution? In what solvent? (3.5 ml, 8.75 mmol) at 195 K under a nitrogen atmosphere. Stirring was continued for 30 min and then octafluorocyclopentene (0.59 ml, 4.36 mmol) was added slowly to the reaction mixture. The mixture was then stirred for 2.5 h at 195 K. The reaction was quenched by the addition of water. After a series of routine operations, the title compound, (Ia) (1.2 g, 2.2 mmol), was obtained in 50.9% yield by column chromatography on SiO2 using CHCl3 as the eluent. The compound was crystallized from chloroform–hexane (1:2, v/v at room temperature and produced crystals suitable for X-ray analysis. The crystals of (Ia) had the following elementary analysis and NMR data: m.p.: 400.4–400.6 K; analysis calculated for C23H22F6O4S2: C 51.11, H 4.10%; found: C 51.23, H 4.20%; 1H NMR (400 MHz, CDCl3, δ, p.p.m.): 0.924–0.961 (t, 6H, J = 7.8 Hz, –CH3), 2.192–2.248 (q, 4H, J = 7.5 Hz, –CH2), 4.002–4.036 (t, 4H, J = 6.8 Hz, –CH2), 4.101–4.136 (t, 4H, J = 7.0 Hz, –CH2), 6.021 (s, 2H, –CH), 7.094 (s, 2H, thiophene-H).
It was obvious from electron-density maps that the CF2 group at C4 was disordered, corresponding with two orientations of the cyclopent-1-ene ring in a C4-envelope conformation. This disorder was readily modelled with atom C4 disordered over two sites (C4 and C4'), with F atoms F41 and F42, and F41' and F42', respectively. DFIX restraints were used to keep the C4—F, C4'—F and F···F separations to be in agreement with the observed C—F geometry at the C3 and C5 sites. Initially, the two disordered orientations were refined with tied occupancy parameters, but as these refined occupancy values were not significantly different from 1/2, the occupancies were then fixed at 0.5 for the final refinement cycles. All H atoms were clearly defined in difference maps and were allowed for as riding atoms, with C—H distances in the range 0.96–0.98 Å and with Uiso(H) = 1.2 and 1.5Ueq(C).
Data collection: XSCANS (Bruker, 1997); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL (Bruker, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
1,2-Bis[5-(1,3-dioxolan-2-yl)-2-ethyl-3-thienyl]-3,3,4,4,5,5- hexafluorocyclopent-1-ene
top
Crystal data top
C23H22F6O4S2 | F(000) = 1112 |
Mr = 540.53 | Dx = 1.489 Mg m−3 |
Monoclinic, P21/n | Melting point: 400 K |
Hall symbol: -P 2yn | Mo Kα radiation, λ = 0.71073 Å |
a = 13.353 (2) Å | Cell parameters from 24 reflections |
b = 13.370 (2) Å | θ = 4.9–12.9° |
c = 13.600 (3) Å | µ = 0.30 mm−1 |
β = 96.796 (11)° | T = 295 K |
V = 2411.0 (7) Å3 | Grain, colourless |
Z = 4 | 0.5 × 0.5 × 0.4 mm |
Data collection top
Bruker P4 diffractometer | Rint = 0.026 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 2.0° |
Graphite monochromator | h = −1→15 |
ω scans | k = −1→15 |
5323 measured reflections | l = −16→16 |
4231 independent reflections | 3 standard reflections every 97 reflections |
3377 reflections with I > 2σ(I) | intensity decay: none |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.049 | H-atom parameters constrained |
wR(F2) = 0.144 | w = 1/[σ2(Fo2) + (0.0639P)2 + 1.2878P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max < 0.001 |
4231 reflections | Δρmax = 0.39 e Å−3 |
340 parameters | Δρmin = −0.29 e Å−3 |
6 restraints | Extinction correction: SHELXTL (Bruker, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0021 (7) |
Crystal data top
C23H22F6O4S2 | V = 2411.0 (7) Å3 |
Mr = 540.53 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 13.353 (2) Å | µ = 0.30 mm−1 |
b = 13.370 (2) Å | T = 295 K |
c = 13.600 (3) Å | 0.5 × 0.5 × 0.4 mm |
β = 96.796 (11)° | |
Data collection top
Bruker P4 diffractometer | Rint = 0.026 |
5323 measured reflections | 3 standard reflections every 97 reflections |
4231 independent reflections | intensity decay: none |
3377 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.049 | 6 restraints |
wR(F2) = 0.144 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.39 e Å−3 |
4231 reflections | Δρmin = −0.29 e Å−3 |
340 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
S11 | 0.61709 (5) | 0.50947 (6) | 0.43250 (7) | 0.0716 (3) | |
S21 | 0.59373 (6) | 0.17217 (6) | 0.73738 (6) | 0.0710 (3) | |
F31 | 0.9032 (2) | 0.0754 (2) | 0.59655 (16) | 0.1218 (9) | |
F32 | 0.81264 (16) | 0.03258 (15) | 0.46600 (19) | 0.1017 (7) | |
F41 | 1.0160 (3) | 0.1798 (4) | 0.5409 (4) | 0.1188 (18) | 0.50 |
F42 | 0.9775 (6) | 0.1094 (5) | 0.4036 (5) | 0.138 (4) | 0.50 |
F41' | 1.0146 (3) | 0.1375 (5) | 0.4464 (6) | 0.100 (2) | 0.50 |
F42' | 0.8857 (4) | 0.1186 (3) | 0.3437 (3) | 0.0966 (13) | 0.50 |
F51 | 0.96866 (15) | 0.32777 (17) | 0.4679 (2) | 0.1165 (9) | |
F52 | 0.87636 (19) | 0.2853 (3) | 0.33976 (16) | 0.1400 (12) | |
O31 | 0.77267 (19) | 0.69553 (15) | 0.39772 (17) | 0.0820 (7) | |
O33 | 0.68496 (19) | 0.70907 (15) | 0.52895 (17) | 0.0808 (6) | |
O41 | 0.41057 (15) | 0.02067 (16) | 0.66613 (16) | 0.0730 (6) | |
O43 | 0.53379 (16) | −0.0541 (2) | 0.7667 (2) | 0.0979 (9) | |
C1 | 0.80209 (18) | 0.27763 (18) | 0.48668 (18) | 0.0483 (5) | |
C2 | 0.78153 (18) | 0.19196 (18) | 0.53188 (18) | 0.0489 (6) | |
C3 | 0.8555 (2) | 0.11210 (19) | 0.5132 (2) | 0.0582 (6) | |
C4 | 0.9400 (4) | 0.1674 (9) | 0.4695 (6) | 0.0657 (15) | 0.50 |
C4' | 0.9157 (4) | 0.1531 (9) | 0.4339 (5) | 0.0657 (15) | 0.50 |
C5 | 0.8948 (2) | 0.2655 (2) | 0.4347 (2) | 0.0576 (6) | |
C12 | 0.6496 (2) | 0.3850 (2) | 0.4398 (2) | 0.0591 (7) | |
C13 | 0.74850 (18) | 0.37359 (18) | 0.47795 (18) | 0.0492 (6) | |
C14 | 0.79658 (19) | 0.46707 (18) | 0.50225 (19) | 0.0520 (6) | |
H14 | 0.8636 | 0.4728 | 0.5295 | 0.062* | |
C15 | 0.7354 (2) | 0.5462 (2) | 0.4819 (2) | 0.0569 (6) | |
C16 | 0.5725 (2) | 0.3066 (2) | 0.4062 (3) | 0.0797 (9) | |
H16A | 0.6075 | 0.2447 | 0.3954 | 0.096* | |
H16B | 0.5312 | 0.2948 | 0.4592 | 0.096* | |
C17 | 0.5054 (4) | 0.3308 (3) | 0.3153 (4) | 0.1203 (17) | |
H17A | 0.4569 | 0.2782 | 0.3014 | 0.180* | |
H17B | 0.5446 | 0.3374 | 0.2609 | 0.180* | |
H17C | 0.4710 | 0.3925 | 0.3244 | 0.180* | |
C22 | 0.6855 (2) | 0.2270 (2) | 0.6762 (2) | 0.0572 (6) | |
C23 | 0.70304 (18) | 0.17008 (18) | 0.59622 (18) | 0.0496 (6) | |
C24 | 0.6430 (2) | 0.08147 (19) | 0.5865 (2) | 0.0556 (6) | |
H24 | 0.6466 | 0.0345 | 0.5365 | 0.067* | |
C25 | 0.5804 (2) | 0.0727 (2) | 0.6570 (2) | 0.0593 (7) | |
C26 | 0.7361 (2) | 0.3200 (2) | 0.7176 (2) | 0.0709 (8) | |
H26A | 0.7893 | 0.3375 | 0.6779 | 0.085* | |
H26B | 0.7674 | 0.3063 | 0.7842 | 0.085* | |
C27 | 0.6668 (3) | 0.4083 (3) | 0.7207 (3) | 0.0992 (12) | |
H27A | 0.7057 | 0.4667 | 0.7409 | 0.149* | |
H27B | 0.6195 | 0.3954 | 0.7672 | 0.149* | |
H27C | 0.6309 | 0.4190 | 0.6562 | 0.149* | |
C32 | 0.7620 (2) | 0.6544 (2) | 0.4910 (2) | 0.0631 (7) | |
H32 | 0.8252 | 0.6623 | 0.5348 | 0.076* | |
C34 | 0.6800 (4) | 0.8022 (3) | 0.4808 (3) | 0.1126 (15) | |
H34A | 0.7109 | 0.8536 | 0.5248 | 0.135* | |
H34B | 0.6103 | 0.8205 | 0.4607 | 0.135* | |
C35 | 0.7335 (4) | 0.7920 (3) | 0.3956 (3) | 0.1049 (13) | |
H35A | 0.6881 | 0.8025 | 0.3353 | 0.126* | |
H35B | 0.7874 | 0.8409 | 0.3980 | 0.126* | |
C42 | 0.5107 (2) | −0.0115 (2) | 0.6726 (2) | 0.0672 (8) | |
H42 | 0.5166 | −0.0628 | 0.6222 | 0.081* | |
C44 | 0.4463 (2) | −0.0716 (3) | 0.8079 (3) | 0.0822 (9) | |
H44A | 0.4467 | −0.0352 | 0.8696 | 0.099* | |
H44B | 0.4390 | −0.1424 | 0.8210 | 0.099* | |
C45 | 0.3633 (2) | −0.0366 (3) | 0.7348 (2) | 0.0751 (8) | |
H45A | 0.3273 | −0.0928 | 0.7022 | 0.090* | |
H45B | 0.3162 | 0.0039 | 0.7664 | 0.090* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
S11 | 0.0526 (4) | 0.0525 (4) | 0.1063 (6) | 0.0090 (3) | −0.0049 (4) | 0.0039 (4) |
S21 | 0.0753 (5) | 0.0754 (5) | 0.0676 (5) | −0.0160 (4) | 0.0308 (4) | −0.0079 (4) |
F31 | 0.1335 (19) | 0.143 (2) | 0.0867 (13) | 0.0869 (17) | 0.0042 (13) | 0.0186 (13) |
F32 | 0.0857 (13) | 0.0736 (12) | 0.151 (2) | −0.0037 (10) | 0.0377 (13) | −0.0458 (12) |
F41 | 0.056 (2) | 0.120 (4) | 0.175 (5) | −0.003 (2) | −0.007 (3) | 0.054 (4) |
F42 | 0.167 (8) | 0.075 (4) | 0.197 (10) | 0.023 (5) | 0.132 (8) | 0.005 (5) |
F41' | 0.056 (3) | 0.080 (5) | 0.169 (7) | 0.024 (3) | 0.040 (3) | 0.007 (4) |
F42' | 0.132 (4) | 0.090 (3) | 0.075 (3) | −0.015 (3) | 0.042 (2) | −0.029 (2) |
F51 | 0.0604 (11) | 0.0989 (15) | 0.199 (3) | −0.0187 (11) | 0.0508 (13) | −0.0499 (16) |
F52 | 0.1163 (18) | 0.239 (3) | 0.0733 (13) | 0.071 (2) | 0.0452 (12) | 0.0389 (16) |
O31 | 0.1070 (17) | 0.0510 (11) | 0.0954 (16) | 0.0094 (11) | 0.0425 (13) | 0.0095 (10) |
O33 | 0.1079 (17) | 0.0520 (11) | 0.0884 (15) | 0.0146 (11) | 0.0371 (13) | 0.0010 (10) |
O41 | 0.0530 (11) | 0.0783 (13) | 0.0878 (14) | −0.0024 (10) | 0.0091 (10) | 0.0252 (11) |
O43 | 0.0567 (12) | 0.1094 (19) | 0.128 (2) | 0.0024 (12) | 0.0135 (12) | 0.0673 (16) |
C1 | 0.0455 (12) | 0.0471 (13) | 0.0533 (13) | 0.0047 (10) | 0.0100 (10) | 0.0023 (10) |
C2 | 0.0478 (13) | 0.0462 (13) | 0.0536 (13) | 0.0036 (10) | 0.0093 (10) | 0.0031 (11) |
C3 | 0.0595 (15) | 0.0474 (14) | 0.0682 (16) | 0.0083 (12) | 0.0099 (13) | 0.0034 (12) |
C4 | 0.045 (3) | 0.058 (3) | 0.096 (6) | 0.002 (3) | 0.018 (3) | −0.017 (4) |
C4' | 0.045 (3) | 0.058 (3) | 0.096 (6) | 0.002 (3) | 0.018 (3) | −0.017 (4) |
C5 | 0.0522 (14) | 0.0603 (16) | 0.0627 (15) | 0.0017 (12) | 0.0173 (12) | 0.0054 (13) |
C12 | 0.0519 (14) | 0.0515 (15) | 0.0728 (17) | 0.0025 (12) | 0.0026 (12) | 0.0028 (13) |
C13 | 0.0474 (13) | 0.0448 (13) | 0.0564 (13) | 0.0029 (10) | 0.0105 (10) | 0.0055 (11) |
C14 | 0.0459 (13) | 0.0486 (13) | 0.0614 (15) | 0.0026 (11) | 0.0067 (11) | 0.0061 (11) |
C15 | 0.0533 (14) | 0.0508 (14) | 0.0664 (16) | 0.0036 (11) | 0.0062 (12) | 0.0011 (12) |
C16 | 0.0618 (17) | 0.0591 (17) | 0.114 (3) | −0.0041 (14) | −0.0057 (17) | −0.0008 (17) |
C17 | 0.111 (3) | 0.094 (3) | 0.141 (4) | −0.017 (2) | −0.048 (3) | −0.002 (3) |
C22 | 0.0549 (14) | 0.0580 (15) | 0.0604 (15) | −0.0047 (12) | 0.0136 (12) | 0.0007 (12) |
C23 | 0.0495 (13) | 0.0486 (13) | 0.0525 (13) | 0.0029 (10) | 0.0128 (10) | 0.0046 (11) |
C24 | 0.0602 (15) | 0.0453 (13) | 0.0637 (15) | 0.0021 (11) | 0.0177 (12) | 0.0029 (11) |
C25 | 0.0579 (15) | 0.0547 (15) | 0.0674 (16) | −0.0026 (12) | 0.0159 (13) | 0.0044 (12) |
C26 | 0.078 (2) | 0.075 (2) | 0.0614 (16) | −0.0200 (16) | 0.0156 (14) | −0.0108 (14) |
C27 | 0.106 (3) | 0.077 (2) | 0.121 (3) | −0.011 (2) | 0.037 (2) | −0.033 (2) |
C32 | 0.0621 (16) | 0.0486 (14) | 0.0775 (18) | 0.0070 (12) | 0.0034 (14) | 0.0009 (13) |
C34 | 0.163 (4) | 0.064 (2) | 0.120 (3) | 0.039 (2) | 0.057 (3) | 0.018 (2) |
C35 | 0.152 (4) | 0.068 (2) | 0.100 (3) | 0.033 (2) | 0.036 (3) | 0.0158 (19) |
C42 | 0.0640 (17) | 0.0569 (16) | 0.084 (2) | −0.0032 (13) | 0.0240 (15) | 0.0066 (14) |
C44 | 0.073 (2) | 0.096 (2) | 0.080 (2) | 0.0002 (18) | 0.0198 (17) | 0.0152 (18) |
C45 | 0.0589 (17) | 0.084 (2) | 0.084 (2) | −0.0083 (15) | 0.0157 (15) | 0.0130 (17) |
Geometric parameters (Å, º) top
S11—C15 | 1.713 (3) | C14—H14 | 0.93 |
S11—C12 | 1.719 (3) | C15—C32 | 1.491 (4) |
S21—C25 | 1.717 (3) | C16—C17 | 1.475 (5) |
S21—C22 | 1.724 (3) | C16—H16A | 0.97 |
F31—C3 | 1.327 (3) | C16—H16B | 0.97 |
F32—C3 | 1.335 (3) | C17—H17A | 0.96 |
F41—C4 | 1.328 (2) | C17—H17B | 0.96 |
F42—C4 | 1.327 (2) | C17—H17C | 0.96 |
F41'—C4' | 1.327 (2) | C22—C23 | 1.370 (4) |
F42'—C4' | 1.327 (2) | C22—C26 | 1.494 (4) |
F51—C5 | 1.329 (3) | C23—C24 | 1.428 (4) |
F52—C5 | 1.312 (3) | C24—C25 | 1.349 (4) |
O31—C35 | 1.392 (4) | C24—H24 | 0.93 |
O31—C32 | 1.405 (4) | C25—C42 | 1.492 (4) |
O33—C34 | 1.404 (4) | C26—C27 | 1.503 (5) |
O33—C32 | 1.409 (4) | C26—H26A | 0.97 |
O41—C42 | 1.397 (4) | C26—H26B | 0.97 |
O41—C45 | 1.413 (4) | C27—H27A | 0.96 |
O43—C44 | 1.373 (4) | C27—H27B | 0.96 |
O43—C42 | 1.402 (4) | C27—H27C | 0.96 |
C1—C2 | 1.344 (3) | C32—H32 | 0.98 |
C1—C13 | 1.467 (3) | C34—C35 | 1.438 (5) |
C1—C5 | 1.505 (3) | C34—H34A | 0.97 |
C2—C23 | 1.472 (3) | C34—H34B | 0.97 |
C2—C3 | 1.496 (3) | C35—H35A | 0.97 |
C3—C4' | 1.523 (11) | C35—H35B | 0.97 |
C3—C4 | 1.528 (12) | C42—H42 | 0.98 |
C4—C5 | 1.498 (11) | C44—C45 | 1.475 (5) |
C4'—C5 | 1.529 (12) | C44—H44A | 0.97 |
C12—C13 | 1.369 (4) | C44—H44B | 0.97 |
C12—C16 | 1.503 (4) | C45—H45A | 0.97 |
C13—C14 | 1.426 (3) | C45—H45B | 0.97 |
C14—C15 | 1.346 (4) | | |
| | | |
C15—S11—C12 | 92.29 (13) | C16—C17—H17C | 109.5 |
C25—S21—C22 | 92.73 (13) | H17A—C17—H17C | 109.5 |
C35—O31—C32 | 107.7 (2) | H17B—C17—H17C | 109.5 |
C34—O33—C32 | 106.6 (3) | C23—C22—C26 | 130.5 (2) |
C42—O41—C45 | 106.9 (2) | C23—C22—S21 | 110.2 (2) |
C44—O43—C42 | 109.6 (2) | C26—C22—S21 | 119.2 (2) |
C2—C1—C13 | 131.2 (2) | C22—C23—C24 | 112.8 (2) |
C2—C1—C5 | 110.3 (2) | C22—C23—C2 | 124.2 (2) |
C13—C1—C5 | 118.4 (2) | C24—C23—C2 | 122.8 (2) |
C1—C2—C23 | 129.8 (2) | C25—C24—C23 | 113.2 (2) |
C1—C2—C3 | 110.9 (2) | C25—C24—H24 | 123.4 |
C23—C2—C3 | 119.3 (2) | C23—C24—H24 | 123.4 |
F31—C3—F32 | 104.5 (3) | C24—C25—C42 | 128.0 (3) |
F31—C3—C2 | 112.3 (2) | C24—C25—S21 | 111.1 (2) |
F32—C3—C2 | 113.3 (2) | C42—C25—S21 | 120.9 (2) |
F31—C3—C4' | 119.9 (3) | C22—C26—C27 | 114.3 (3) |
F32—C3—C4' | 100.2 (3) | C22—C26—H26A | 108.7 |
C2—C3—C4' | 106.1 (4) | C27—C26—H26A | 108.7 |
F31—C3—C4 | 102.1 (3) | C22—C26—H26B | 108.7 |
F32—C3—C4 | 119.5 (3) | C27—C26—H26B | 108.7 |
C2—C3—C4 | 104.7 (4) | H26A—C26—H26B | 107.6 |
F42—C4—F41 | 104.46 (11) | C26—C27—H27A | 109.5 |
F42—C4—C5 | 117.9 (8) | C26—C27—H27B | 109.5 |
F41—C4—C5 | 111.5 (7) | H27A—C27—H27B | 109.5 |
F42—C4—C3 | 109.5 (8) | C26—C27—H27C | 109.5 |
F41—C4—C3 | 108.2 (7) | H27A—C27—H27C | 109.5 |
C5—C4—C3 | 105.0 (3) | H27B—C27—H27C | 109.5 |
F42'—C4'—F41' | 104.52 (11) | O31—C32—O33 | 106.5 (2) |
F42'—C4'—C3 | 113.7 (7) | O31—C32—C15 | 110.7 (2) |
F41'—C4'—C3 | 117.0 (8) | O33—C32—C15 | 110.9 (2) |
F42'—C4'—C5 | 108.2 (7) | O31—C32—H32 | 109.6 |
F41'—C4'—C5 | 109.5 (8) | O33—C32—H32 | 109.6 |
C3—C4'—C5 | 103.7 (3) | C15—C32—H32 | 109.6 |
F52—C5—F51 | 104.7 (3) | O33—C34—C35 | 106.9 (3) |
F52—C5—C4 | 120.6 (3) | O33—C34—H34A | 110.3 |
F51—C5—C4 | 100.7 (3) | C35—C34—H34A | 110.3 |
F52—C5—C1 | 111.8 (2) | O33—C34—H34B | 110.3 |
F51—C5—C1 | 113.1 (2) | C35—C34—H34B | 110.3 |
C4—C5—C1 | 105.6 (4) | H34A—C34—H34B | 108.6 |
F52—C5—C4' | 101.8 (3) | O31—C35—C34 | 107.0 (3) |
F51—C5—C4' | 119.3 (3) | O31—C35—H35A | 110.3 |
C1—C5—C4' | 105.7 (4) | C34—C35—H35A | 110.3 |
C13—C12—C16 | 129.2 (2) | O31—C35—H35B | 110.3 |
C13—C12—S11 | 110.8 (2) | C34—C35—H35B | 110.3 |
C16—C12—S11 | 119.9 (2) | H35A—C35—H35B | 108.6 |
C12—C13—C14 | 112.2 (2) | O41—C42—O43 | 106.7 (2) |
C12—C13—C1 | 124.6 (2) | O41—C42—C25 | 111.6 (2) |
C14—C13—C1 | 123.1 (2) | O43—C42—C25 | 111.3 (3) |
C15—C14—C13 | 113.3 (2) | O41—C42—H42 | 109.1 |
C15—C14—H14 | 123.4 | O43—C42—H42 | 109.1 |
C13—C14—H14 | 123.4 | C25—C42—H42 | 109.1 |
C14—C15—C32 | 127.8 (3) | O43—C44—C45 | 106.2 (3) |
C14—C15—S11 | 111.4 (2) | O43—C44—H44A | 110.5 |
C32—C15—S11 | 120.7 (2) | C45—C44—H44A | 110.5 |
C17—C16—C12 | 115.3 (3) | O43—C44—H44B | 110.5 |
C17—C16—H16A | 108.4 | C45—C44—H44B | 110.5 |
C12—C16—H16A | 108.4 | H44A—C44—H44B | 108.7 |
C17—C16—H16B | 108.4 | O41—C45—C44 | 105.0 (2) |
C12—C16—H16B | 108.4 | O41—C45—H45A | 110.7 |
H16A—C16—H16B | 107.5 | C44—C45—H45A | 110.7 |
C16—C17—H17A | 109.5 | O41—C45—H45B | 110.7 |
C16—C17—H17B | 109.5 | C44—C45—H45B | 110.7 |
H17A—C17—H17B | 109.5 | H45A—C45—H45B | 108.8 |
| | | |
C13—C1—C2—C23 | −6.9 (5) | S21—C22—C23—C24 | −1.0 (3) |
C5—C1—C2—C23 | 175.8 (2) | C26—C22—C23—C2 | 0.3 (5) |
C13—C1—C2—C3 | 175.7 (2) | S21—C22—C23—C2 | −175.78 (19) |
C5—C1—C2—C3 | −1.7 (3) | C1—C2—C23—C22 | −50.2 (4) |
C1—C2—C3—C4' | −10.0 (3) | C3—C2—C23—C22 | 127.0 (3) |
C23—C2—C3—C4' | 172.3 (3) | C1—C2—C23—C24 | 135.5 (3) |
C1—C2—C3—C4 | 12.8 (3) | C3—C2—C23—C24 | −47.2 (3) |
C23—C2—C3—C4 | −164.9 (3) | C22—C23—C24—C25 | 0.9 (3) |
C2—C3—C4—C5 | −18.5 (4) | C2—C23—C24—C25 | 175.7 (2) |
C2—C3—C4'—C5 | 16.8 (3) | C23—C24—C25—C42 | −177.0 (3) |
C3—C4—C5—C1 | 17.6 (4) | C23—C24—C25—S21 | −0.3 (3) |
C2—C1—C5—C4 | −10.4 (3) | C22—S21—C25—C24 | −0.3 (2) |
C13—C1—C5—C4 | 171.8 (3) | C22—S21—C25—C42 | 176.7 (2) |
C2—C1—C5—C4' | 12.6 (3) | C23—C22—C26—C27 | 120.8 (4) |
C13—C1—C5—C4' | −165.1 (3) | S21—C22—C26—C27 | −63.4 (3) |
C3—C4'—C5—C1 | −17.7 (3) | C35—O31—C32—O33 | 21.7 (4) |
C15—S11—C12—C13 | −0.6 (2) | C35—O31—C32—C15 | 142.3 (3) |
C15—S11—C12—C16 | 179.3 (3) | C34—O33—C32—O31 | −23.2 (4) |
C16—C12—C13—C14 | −179.2 (3) | C34—O33—C32—C15 | −143.7 (3) |
S11—C12—C13—C14 | 0.8 (3) | C14—C15—C32—O31 | 102.0 (3) |
C16—C12—C13—C1 | 5.0 (5) | S11—C15—C32—O31 | −73.1 (3) |
S11—C12—C13—C1 | −175.0 (2) | C14—C15—C32—O33 | −140.0 (3) |
C2—C1—C13—C12 | −56.1 (4) | S11—C15—C32—O33 | 44.9 (3) |
C5—C1—C13—C12 | 121.0 (3) | C32—O33—C34—C35 | 16.0 (5) |
C2—C1—C13—C14 | 128.5 (3) | C32—O31—C35—C34 | −11.6 (5) |
C5—C1—C13—C14 | −54.3 (3) | O33—C34—C35—O31 | −2.7 (6) |
C12—C13—C14—C15 | −0.6 (3) | C45—O41—C42—O43 | −23.5 (3) |
C1—C13—C14—C15 | 175.3 (2) | C45—O41—C42—C25 | −145.3 (3) |
C13—C14—C15—C32 | −175.3 (3) | C44—O43—C42—O41 | 14.8 (4) |
C13—C14—C15—S11 | 0.1 (3) | C44—O43—C42—C25 | 136.8 (3) |
C12—S11—C15—C14 | 0.3 (2) | C24—C25—C42—O41 | −120.4 (3) |
C12—S11—C15—C32 | 176.1 (2) | S21—C25—C42—O41 | 63.2 (3) |
C13—C12—C16—C17 | −139.8 (4) | C24—C25—C42—O43 | 120.5 (3) |
S11—C12—C16—C17 | 40.2 (5) | S21—C25—C42—O43 | −55.9 (3) |
C25—S21—C22—C23 | 0.8 (2) | C42—O43—C44—C45 | −0.5 (4) |
C25—S21—C22—C26 | −175.8 (2) | C42—O41—C45—C44 | 22.7 (4) |
C26—C22—C23—C24 | 175.1 (3) | O43—C44—C45—O41 | −13.6 (4) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C35—H35A···F52i | 0.97 | 2.45 | 3.361 (5) | 157 |
Symmetry code: (i) −x+3/2, y+1/2, −z+1/2. |
Experimental details
Crystal data |
Chemical formula | C23H22F6O4S2 |
Mr | 540.53 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 295 |
a, b, c (Å) | 13.353 (2), 13.370 (2), 13.600 (3) |
β (°) | 96.796 (11) |
V (Å3) | 2411.0 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.30 |
Crystal size (mm) | 0.5 × 0.5 × 0.4 |
|
Data collection |
Diffractometer | Bruker P4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5323, 4231, 3377 |
Rint | 0.026 |
(sin θ/λ)max (Å−1) | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.049, 0.144, 1.05 |
No. of reflections | 4231 |
No. of parameters | 340 |
No. of restraints | 6 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.39, −0.29 |
Selected bond lengths (Å) topS11—C15 | 1.713 (3) | C2—C23 | 1.472 (3) |
S11—C12 | 1.719 (3) | C2—C3 | 1.496 (3) |
S21—C25 | 1.717 (3) | C3—C4' | 1.523 (11) |
S21—C22 | 1.724 (3) | C3—C4 | 1.528 (12) |
C1—C2 | 1.344 (3) | C4—C5 | 1.498 (11) |
C1—C13 | 1.467 (3) | C4'—C5 | 1.529 (12) |
C1—C5 | 1.505 (3) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C35—H35A···F52i | 0.97 | 2.45 | 3.361 (5) | 157 |
Symmetry code: (i) −x+3/2, y+1/2, −z+1/2. |
Subscribe to Acta Crystallographica Section C: Structural Chemistry
The full text of this article is available to subscribers to the journal.
If you have already registered and are using a computer listed in your registration details, please email
support@iucr.org for assistance.
Photochromic compounds have been extensively investigated for their possible application in optoelectronics, such as optical memories, photoswitches and waveguides (Crano & Guglielmetti, 1999). Among all photochromic systems, diarylethene derivatives are the most promising candidates for optical memories and other optoelectronic devices because of the good thermal stability of the two isomers and their high sensitivity, fast response and high fatigue resistance (Irie, 2000; Tian & Yang, 2004). Generally, diarylethenes with thiophene heterocyclic rings have two interconverting conformations in almost equal amounts in solution, i.e. anti-parallel and parallel conformations (Irie & Mohri, 1988; Uchida et al., 1990); only anti-parallel conformations can undergo effective photocyclization reactions by a conrotatory mechanism, while the parallel conformations are photochemically inactive (Yamada et al., 2000). However, there is no interconversion between the two conformers in the crystalline phase of diarylethenes and the molecules are regularly oriented in a fixed conformation (Pu et al., 2003, 2004, 2005), except for one example (Kobatake et al., 2005) where there are two independent molecules with different conformations in the asymmetric unit. In addition, photochromic diarylethene crystals with an anti-parallel conformation can reversibly turn various colours (yellow, red, blue or green) from colourless, depending on their molecular structure, upon irradiation with UV and appropriate wavelength visible light (Kobatake & Irie, 2004). These crystals also exhibit good thermal stability of the two isomers and remarkable fatigue resistance. Crystals of diarylethenes in the anti-parallel conformation are thus very promising for practical applications.
In the present work, the title photochromic diarylethene, (Ia), was synthesized. We have previously reported (Pu et al., 2002) the structure of the 2-methyl analogue, (II), of this compound. In order to investigate systematically the substituent effect at the 2-position of the thiophene of diarylethenes on their photochemical properties, we have now determined the structure of the title compound, (Ia). The 2-methyl and 2-ethyl compounds differ from each other, not only in their crystal structures but also in various photochemical properties, such as their absorption maxima, ease of cyclization, cycloreversion quantum yield and oxidation–reduction potentials.
The molecular structure of (Ia) is shown in Fig. 1, a packing diagram is shown in Fig. 2 and selected geometric parameters are given in Table 1. As shown in Fig. 1(a), the molecule has approximate twofold symmetry, with the two thiophene rings in a photoactive anti-parallel conformation in the crystal. The hexafluorocyclopentene ring adopts a C4-envelope conformation with the flap atom (C4) equally disordered over two sites (C4 and C4'), with concomitant disorder of the attached F atoms (see Fig. 1b, with details in the Experimental section). In the cyclopent-1-ene ring, the C1—C2 bond is clearly a double bond, and the other bonds from C1 and C2 (Table 1) are clearly single bonds.
The two independent planar thiophene ring systems have essentially identical geometries and the dihedral angles between the central cyclopent-1-ene ring and the adjacent thiophene rings are 55.38 (7) and 54.81 (9)°. The corresponding values in the methyl analogue, (II), are both 49°. This conformation leads to a C12···C22 separation of 3.829 (4) Å [compared with 3.67 Å in (II)], which is short enough, theoretically, for a ring-closure reaction to take place in the crystalline phase (Ramamurthy & Venkatesan, 1987) to generate compound (Ib). The orientations of the ethyl groups at C12 and C22 are defined by the torsion angles C13—C12—C16—C17 [−139.8 (4)°] and C23—C22—C26—C27 [120.8 (4)°].
The two terminal 1,3-dioxolane rings both have envelope conformations; the O31/C32/O33/C34/C35 ring has a C32-envelope conformation, while the O41/C42/O43/C44/C45 ring adopts an O41-envelope form. Their orientations relative to the thiophene rings are presumably largely determined by crystal-packing considerations and lead to torsion angles H32—C32—C15—S11 166° and H42—C42—C25—S21 − 176°.
In the crystal, molecules related by a 21 screw axis are linked by weak C—H···F intermolecular interactions from one of the dioxolane C—H groups to generate chains extending along the b direction, as shown in Fig. 2; details are given in Table 2.
Crystals of (Ia) showed photochromic reaction in accordance with the expected ring closure, to form (Ib). Upon irradiation with light of wavelength 254 nm, the colourless crystals of (Ia) quickly became magenta-coloured, as shown in Fig. 3. When observed under polarized light, the intensity of the magenta colour changed on rotation of the crystalline sample. This phenomenon suggests that the closed-ring molecules of (Ib) are packed regularly in the crystal, but we have not been able to establish the crystal structure of (Ib). When the magenta crystal was dissolved in hexane, the solution was magenta-coloured and the absorption maximum was observed at 542 nm, consistent with the presence of the closed-ring isomer, (Ib). The magenta colour disappeared upon irradiation with light of wavelength 510 nm or daylight, and the absorption spectrum of the solution containing the colourless material was the same as that of solutions of the open-ring isomer, (Ia).