doi: 10.1038/nature05669 SUPPLEMENTARY INFORMATION Reversible Shape Changes of Molecular Crystals by Photoirradiation Seiya Kobatake 1, Shizuka Takami, Hiroaki Muto, Tomoyuki Ishikawa 1 & Masahiro Irie 1 Department of Applied Chemistry, Graduate School of Engineering, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Hakozaki 6-10-1, Fukuoka 81-8581, Japan 1 1
Supplementary Methods Sample Preparation. 1,-Bis(-ethyl-5-phenyl-3-thienyl)perfluorocyclopentene (1) and 1,-bis(5-methyl--phenyl-4-thiazolyl)perfluorocyclopentene () were prepared according to the methods reported previously S1,S. The micrometer-size single crystals were prepared by sublimation of the compounds on glass plates or KBr substrates. Photographs were taken with a digital camera (NIKON Coolpix 4500 Microsystem, 4.0 megapixels) connected with a Leica DMLP or Nikon E-600Pol polarizing microscope. Ultraviolet light irradiation was carried out using a Keyence UV-400 UV-LED (maximum power 50 mw/cm at 365 nm). Visible light irradiation was carried out using a xenon-mercury lamp (00 W, Moritex MUV-0U) as a light source. The light longer than 500 nm was obtained by passing the light through a cut-off filter (Asahi Techno glass Y-50). Infrared Absorption Spectral Measurement. To know the conversion ratio from the open- to the closed-ring isomers of the single crystals, the photochromic reaction was followed by an infrared (IR) absorption microspectroscopy. IR absorption spectra of thin single crystal 1 were measured with a JASCO Irtron IRT-30 infrared microspectroscopy connected with FT/IR-430. The spectra were taken under polarized IR light to avoid an overlap of peaks. Figure S1 shows the IR spectral changes of crystal 1 upon irradiation with 365 nm light. The open-ring isomer in the crystal has two characteristic bands at 160 and 1350 cm -1. The band at 1350 cm -1 was split into two peaks upon irradiation with UV light, whereas the band at 160 cm -1 monotonously decreased. The closed-ring isomer has no absorption around 160 cm -1. The conversion ratio from the open- to the closed-ring isomers can be determined from the decrease of the band at 160 cm -1. Almost 70% conversion was observed at the photostationary state under irradiation with 365 nm light.
Visible Absorption Spectral Changes of Single Crystal 1. Figure Sa shows the absorption spectral change of single crystal 1 upon irradiation with 365 nm light. The absorption maximum initially remained constant at 65 nm and then shifted to 585 nm. Figure Sb shows the bleaching process of the visible absorption band. The absorption band around 600 nm decreased upon irradiation with visible light. The absorption maximum also showed a bathochromic shift upon photobleaching. Reversibility of Corner Angle of a Single Crystal 1. Figure S3 shows the reversibility of corner angle changes of a square single crystal 1. A square single crystal 1 (11.0 11.5 0.6 micrometer) was irradiated with UV (365 nm) and visible (> 500 nm) light for 1 and 3 min., respectively. Upon UV light irradiation, the square single crystal 1 with corner angle of 88 o changed to lozenge with corner angle of 8 o. The lozenge crystal 1 again became the original square shape upon irradiation with visible light. It was possible to repeat the cycles more than 0 cycles. Measurement of Response Time of Deformation. A rod-like crystal of compound was used for the response time measurement, because even low power single pulsed laser can induce the bending of the rod-like crystal. As a light source, the pulsed laser of the third harmonics of Nd-YAG laser (355 nm, pulse width = 8 ns, power = 60 mj/pulse, INDI-40-10, Spectra-Physics) was used. The bending behavior induced by the single pulsed laser was measured using a high-speed camera (Phantom V7., Vision Research Inc.) with an image intensifier (C6653MOD, Hamamatsu Photonics). Figure S4 shows the images of the bending behavior of the rod-like crystal (53 3 3 micrometer). The exposure time of each frame was 5 microseconds (40,000 frames/sec.). After irradiation with the single pulsed laser the straight rod-like crystal bent and the bending process was almost completed in one frame. This means that the bending rate or the response time of the bending shape change is around 5 microseconds. 3
General Procedure of X-ray Crystallographic Analysis. X-ray crystallographic analysis was performed using a Bruker SMART1000 CCD-based diffractometer (50 kv, 40 ma) with MoK α radiation. The crystal was cooled to 13 K with a cryostat (Rigaku GN). The data were collected as a series of ω-scan frames, each with a width of 0.3 /frame. The crystal-to-detector distance was 5.118 cm. Crystal decay was monitored by repeating the 50 initial frames at the end data collection and analyzing the duplicate reflections. Data reduction was performed using SAINT software, which corrects for Lorentz and polarization effects, and decay. The cell constants were determined by the global refinement. The structures were solved by direct methods using SHELXS-86 S3 and refined by full least-squares on F using SHELXL-97 S4. The positions of all hydrogen atoms were calculated geometrically and refined by the riding model. In least-squares refinements disordered structures were refined using geometrical restraints. For each disordered structure, occupancy factors were refined under a constraint such that the sum is 1. X-ray Crystallographic Analysis of Crystal 1. Figure S5 shows the ORTEP drawings of the open- and closed-ring isomers S1. In situ X-ray crystallographic analysis was carried out for a relatively large crystal (0.3 mm 0. mm 0. mm) to confirm the crystalline photochromic reactions. Table S1 shows X-ray crystallographic data for crystal 1o S1, the UV irradiated crystal 1c and 1c S1. Before photoirradiation, the R1 for the reflection with I > σ(i) and wr for all data are 0.038 and 0.100, respectively. The heights of the residual electron peaks are below 0.8 eå -3. The molecular structure of 1 in the crystal is consisting of independent disordered structures for fluorine atoms and ethyl groups. Figure S5b shows ORTEP drawing of 1c. The crystal structure before UV irradiation was used as the initial model for the refinement. After the difference Fourier synthesis, four new peaks appeared around the sulfur atoms and the carbon atoms on the reacting position. These are assigned to those of the photogenerated closed-ring isomer. The R1 for the reflection with I > σ(i) and wr for all data are 0.055 and 0.15, 4
respectively. The heights of the residual electron peaks are below 0.40 eå -3. The occupancy of the sulfur and carbon atoms in the open- and closed-ring isomers converged to 9:8, respectively. This means the conversion of 8%. Although appreciable shape change is not expected at such low conversion according to Figure a, the contraction of c-axis was observed in the cell parameter. The crystal data of UV irradiated crystal 1c are deposited at the Cambridge Crystallographic Data Centre. (CCDC-69166) S5. X-ray Crystallographic Analysis of Crystal. Figure S6 shows the molecular packing diagram of rectangular and rod-like crystal, and Figure S7 shows ORTEP drawings of o, c and c showing 50% probability displacement ellipsoids. Table S shows X-ray crystallographic data for crystal o S6, UV irradiated crystal c and the isolated closed-ring isomer crystal c. In situ X-ray crystallographic analysis was also carried out using a relatively large crystal (0. mm 0.1 mm 0.05 mm). Upon irradiation with 400-nm light for 7 h, the colourless crystal o turned deep red. The crystal structure before photoirradiation was used as the initial model. After the first least-square refinement, two high electron density peaks Q1 (1.34 eå -3 ) and Q (1.07 eå -3 ), which are ascribed to the sulfur atoms of the photogenerated closed-ring isomer c, appeared near sulfur atoms of o. Furthermore, electron density peaks corresponding to two carbon atoms at the reacting position appeared. The occupancy of the sulfur and carbon atoms in the open- and the closed-ring isomers converged to 93:7, respectively. This means the conversion of 7 %. Although appreciable contraction is not expected at such low conversion according to Figure b, the contraction of a-axis was observed in the cell parameter. Figure S6c and d show the molecular packing diagram of rod-like crystal. The crystal data of UV irradiated crystal c and closed-ring isomer crystal c are deposited at the Cambridge Crystallographic Data Centre. (CCDC-6801 for c) S7 and (CCDC-69167 for c ) S7. 5
Schematic Illustration of the Photocontraction of Single Crystal 1. Figure S8 show the schematic illustration of the photocontraction of single crystal 1. Upon irradiation with UV light the open-ring isomers (black line) converted to the closed-ring isomers (blue line). The transformation rate is reported to be less than 10 ps. 17 The closed-ring isomers were stacked one by one in around 5 microseconds. The molecular stacking resulted in the macroscopic contraction of the crystal along the c-axis. References S1. Kobatake, S., Shibata, K., Uchida, K. & Irie, M. J. Am. Chem. Soc., 1, 1135-1141 (000). S. Uchida, K., Ishikawa, T., Takeshita, M. & Irie, M. Tetrahedron, 54, 667-6638 (1998). S3. Sheldrick, G. M. Acta Crystallogr., Sect. A, 46, 467-473 (1990). S4. Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refinement; Universität Göttingen: Göttingen, 1997. S5. UV irradiated crystal 1c : CCDC-69166. S6. Kuroki, L., Takami, S., Shibata, K. & Irie, M. Chem. Commun. 6005-6007 (005). S7. Open-ring isomer crystal o: CCDC 8860, Closed-ring isomer crystal c: CCDC 6801. UV irradiated crystal c : CCDC-69167. 6
Table S1. X-ray crystallographic data of 1o, 1c a), and 1c 1o 1c (Conversion 8%) 1c Empirical formula C 9 H F 6 S C 9 H F 6 S Formula weight 548.61 548.61 Temperature 13() K 13() K Crystal system orthorhombic monoclinic Space group Pbcn C/c Unit cell dimensions a =.33(5) Å a =.98(5)Å a = 9.76(6)Å b = 10.991() Å b = 11.040(3)Å b = 1.47()Å c = 10.601() Å c = 10.59(3)Å c = 13.44(3)Å β = 100.719(3) o Volume 60.0(9) Å 3 607.4(10) Å 3 4878.(16) Å 3 Z 4 4 8 Density(calculated) 1.400 g/cm 3 1.398 g/cm 3 1.494 g/cm 3 Goodness-of-fit on F 1.085 1.035 0.969 Final R indices [I > σ(i)] R1 = 0.038 R1 = 0. 055 R1 = 0. 041 wr = 0.091 wr = 0.15 wr = 0.095 R indices (all data) R1 = 0.059 R1 = 0. 111 R1 = 0. 068 wr = 0.100 wr = 0.15 wr = 0.106 a) 1c indicates the photoirradiated crystal. 7
Table S. X-ray crystallographic data of o, c a), and c o c (Conversion 7%) c Empirical formula C 5 H 16 F 6 N S C 5 H 16 F 6 N S Formula weight 5.53 5.53 Temperature 13() K 13() K Crystal system monoclinic monoclinic Space group P 1 /n P 1 /c Unit cell dimensions a = 7.36() Å a = 7.186(4)Å a = 11.883()Å b = 5.75(8) Å b = 5.888()Å b = 18.383()Å c = 1.611(4)Å c = 1.640(8)Å c = 11.8745()Å β = 10.43(5) o β = 10.355(4) o β = 118.5760(1) o Volume 95.0(1) Å 3 307.0() Å 3 49.61(6) Å 3 Z 4 4 4 Density(calculated) 1.51 g/cm 3 1.504 g/cm 3 1.543 g/cm 3 Goodness-of-fit on F 0.989 0.984 1.604 Final R indices [I > σ(i)] R1 = 0.058 R1 = 0. 069 R1 = 0. 068 wr = 0.16 wr = 0.159 wr = 0.07 R indices (all data) R1 = 0.115 R1 = 0. 148 R1 = 0.080 wr = 0.153 wr = 0.196 wr = 0.19 a) c indicates the photoirradiated crystal. 8
Absorbance 0.4 0.3 0. Time (s) 0 5 10 15 0 5 30 40 50 60 Conversion (%) 0 33 50 57 61 63 66 70 71 7 0 s 5 10 15 0 5 30 40 50 60 0.1 0 1800 1600 1400 100 Wavelength / nm 1000 800 Figure S1. IR spectral changes of single crystal 1 upon irradiation with 365 nm light. 9
Absorbance 1.0 0.8 0.6 0.4 a before UV UV s UV 4s UV 7s UV 10s UV 15s UV 5s UV 45s UV 80s UV 10s UV 160s UV 00s 0. 0.0 500 600 700 800 Wavelength / nm Absorbance 1.0 0.8 0.6 0.4 b UV 00s vis.30s vis.60s vis.90s vis.10s vis.150s vis.180s vis.5s vis.70s vis.315s vis.360s vis.40s vis.480s vis.50s 0. 0.0 500 600 700 800 Wavelength / nm Figure S. Visible absorption spectral changes of 1 upon irradiation with a UV light (365 nm, Power: ca. 60 mw/cm ) and b visible light (λ > 500 nm). 10
90 88 θ / degree 86 84 8 80 0 5 10 15 0 Cycle number Figure S3. Reversibility of corner angle changes of single crystal 1 upon alternate irradiation with UV (365 nm) and visible (> 500 nm) light. UV (365 nm) and visible (> 500 nm) light was irradiated for 1 and 3 min., respectively. 11
Figure S4. Images of bending behavior of the rod-like crystal (53 3 3 micrometer) taken with a high-speed camera (Phantom V7., Vision Research Inc.) with an image intensifier (C6653MOD, Hamamatsu Photonics). The exposure time of each frame was 5 microseconds (40,000 frames/sec). The numbers above the images are frame numbers. The crystal was irradiated with a single pulsed laser (355 nm, pulse width = 8 nsec, power = 60 mj/pulse, INDI-40-10, Spectra-Physics) at the second frame. The bright spot was an anthracene crystal, which gave fluorescence upon the pulsed laser irradiation. Before the pulse irradiation the rod-like crystal was straight, while it bent after the irradiation and the bending was almost completed in one frame (in the third frame). The rod-like crystal slightly further bent in the fourth frame. This means the bending rate is around 5 microseconds. 0 µm 1
Figure S5. ORTEP drawings of 1 oriented as in the top row of Figure 4b showing 50% probability displacement ellipsoids. The fluorine atoms and ethyl groups were disordered. Only a major conformation was illustrated for clarity. a, open-ring isomer 1o, b, closed-ring isomer in the photoirradiated crystal 1c, c, closed-ring isomer 1c. 13
a Viewed from (010) face b Viewed from (00-1) face 0 a c b a 0 c 70 110 c Viewed from (01) face a 0 c d Viewed from (0-11) face a 0 c b b (01) (0-11) Figure S6. The molecular-packing diagrams of rectangular crystal (a, b) and rod-like crystal (c, d). Below a and b are outlines of the crystal morphology in the same orientation. The red arrows show the direction of contraction of the crystal (a-axis). a: viewed from (010) face. b: viewed from (00-1) face. c: viewed from (01) face. d: viewed from (0-11) face. 14
Figure S7. ORTEP drawings of oriented as in the top row of Figure S6b showing 50% probability displacement ellipsoids. Only a major conformation was illustrated for clarity. a, open-ring isomer o, b, closed-ring isomer in the photoirradiated crystal c, c, closed-ring isomer c. 15
Figure S8. Schematic illustration of photocontraction of the crystal 1 viewed from (010) face. Upon irradiation with UV light the open-ring isomers (black line) converted to the closed-ring isomers (blue line). The transformation rate was faster than nanosecond. The closed-ring isomers were stacked one by one in around 5 microseconds. The molecular stacking resulted in the macroscopic contraction of the crystal along the c-axis. 16