Supporting Information Reversible Light-Directed Red, Green and Blue Reflection with Thermal Stability Enabled by a Self-rganized Helical Superstructure Yannian Li, Augustine Urbas, and Quan Li *, Liquid Crystal Institute, Kent State University, Kent, hio 44242, United States Materials and Manufacturing Directorate, Air Force Research Laboratory WPAFB, hio 45433, United States *E-mail: qli1@kent.edu Contents: 1. General Information. 2. Synthesis of Light-driven Dithienylethene Chiral Switches (S,S)-1 and (R,R)-1 3. Conformation Analysis of (S,S)-1 4. Photoisomerization and Spectra Data of (S,S)-1 in rganic Solvent. 5. Microscopic Textures and Pitch Changes Induced by Photoisomerization of (S,S)-1 in Nematic LC. 6. Measurement of Pitch and Helical Twisting Power. 7. References. 8. Copies of 1 H NMR and 13 C NMR SI1
1. General information All chemicals and solvents were purchased from commercial supplies and used without further purification. 1 H and 13 C NMR spectra were recorded on 400 or 200 MHz spectrometer in CDCl 3 or THF-d 8. Chemical shifts are in δ units (ppm) with the residual solvent peak or TMS as the internal standard. The coupling constant (J) is reported in hertz (Hz). NMR splitting patterns are designated as follows: s, singlet; d, doublet; t, triplet; and m, multiplet. Column chromatography was carried out on silica gel (230-400 mesh). Analytical thin layer chromatography (TLC) was performed on commercially coated 60 mesh F 254 glass plates. Spots were rendered visible by exposing the plate to UV light. Melting points are uncorrected. Mass spectral data were measured with ESI ion mode. Textures and disclination line distance changes were observed by optical microscopy with temperature controller. UV-vis and Cicular dichroism (CD) spectra were collected at room temperature. The UV and visible light irradiation was carried out Xenon light source (100W) through a filter at 310 nm or 550 nm. Reflection spectra were measured with a spectrometer in the dark. The achiral nematic liquid crystals E7 and 5CB were commercially available. E7 is a eutectic mixture of LC components commercially designed for display applications and 5CB is 4 -pentyl-4-biphenylcarbonitrile (Figure S1). CN (5CB) 51% CN (7CB) 25% CN (8CB) 16% CN (5CT) 8% Figure S1. Chemical structures and composition of E7. SI2
2. Synthesis of light-driven axially chiral switches (S,S)-1 and (R,R)-1 Intermediate 2 was synthesis by a known procedure 1 and the characterization data were in accordance with the reference. Figure S2. Synthesis of intermediate 2. Intermediates (S)-4 and (R)-4 were synthesized starting from (S) and (R)-1,1 -Binaphthol in two steps, respectively. Figure S3. Synthesis of intermediates (S)-4 and (R)-4. The target compounds (S,S)-1 and (R,R)-1 were synthesized from 2 and (S)-4 or (R)-4 by a Suzuki coupling reaction, respectively. Figure S4. Synthesis of (S,S)-1 and (R,R)-1. SI3
(S)-2,2'- Methylenedioxy-1,1'-binaphthyl (S)-3 2 A mixture of (S)-1,1 -bi(2-naphthol) (1.43 g, 5 mmol), diiodomethane (4.01 g, 15 mmol) and anhydrous K 2 C 3 (4.14 g, 30 mmol) in acetone (50 ml) was stirred magnetically and refluxed until the reaction was complete as monitored by TLC. After cooling to room temperature, the reaction mixture was poured into water and extracted with ether (3 50 ml). The combined organic layer was washed with water, dried over Na 2 S 4 and concentrated. The crude product was purified by flash column chromatography over silica gel to give the product as white solid (1.37 g, 92%). Mp: 186-188 o C. 1 H NMR (CDCl 3, 200 MHz) δ = 8.01-7.92 (m, 4H), 7.54-7.41 (m, 6H), 7.35-7.30 (m, 2H), 5.70 (s, 2H). 13 C NMR (CDCl 3, 50 MHz) δ = 151.2, 132.2, 131.8, 130.3, 128.4, 126.9, 126.08, 126.05, 125.0, 120.9, 103.1. HRMS (ESI) calcd for C 21 H 14 2 Na + : 321.0891, found: 321.0898. (R)-2,2'-Methylenedioxy-1,1'-binaphthyl (R)-3 3 This intermediate was prepared by the same procedure as that used for (S)-3 from (R)-1,1 -bi(2-naphthol). The spectral data are the same as those for (S)-3. Mp: 187-189 o C. HRMS (ESI) calcd for C 21 H 14 2 Na + : 321.0891, found: 321.0891. SI4
I (S)-3-Iodo-2,2'-methylenedioxy-1,1'-binaphthyl (S)-4 To a THF solution (40 ml) of (S)-3 (596 mg, 2 mmol) at -78 o C under nitrogen was added t-buli (1.5 ml, 1.7 M in pentane, 2.5 mmol). The solution was stirred at this temperature for 1h. To the resulting solution was added a solution of I 2 (660 mg, 2.6 mmol) in THF (10 ml). The reaction mixture was allowed to warm to room temperature and stirred for an additional 10 h. The excess iodine was reduced with 1M Na 2 S 2 3. The reaction mixture was allowed to warm to room temperature, poured into water, and extracted with ethyl acetate (2 20 ml). The combined organic layers were dried over Na 2 S 4 and concentrated. The residue was purified by flash column chromatography to give the product as white solid (382 mg, 45%). Mp: 208-210 o C. 1 H NMR (CDCl 3, 400 MHz) δ = 8.50 (s, 1H), 8.00 (d, J = 9.2 Hz, 1H), 7.94 (dd, J = 8.8, 1.2 Hz, 1H), 7.83 (d, J = 8.4 Hz, 1H), 7.50-7.43 (m, 5H), 7.33-7.28 (m, 2H), 5.71 (d, J = 3.6 Hz, 1H), 5.67 (d, J = 3.6 Hz, 1H). 13 C NMR (CDCl 3, 50 MHz) δ = 151.5, 149.3, 139.2, 133.1, 132.0, 131.7, 130.7, 128.4, 127.3, 127.0, 126.9, 126.7, 126.5, 126.2, 125.8, 125.1, 120.8, 102.6, 90.2. Anal Calcd for C 21 H 13 I 2 : C, 59.45, H, 3.09; found: C, 59.22, H, 2.94. HRMS (ESI) calcd for C 21 H 13 I 2 Na + : 446.9858, found: 446.9840. I SI5
(R)-3-Iodo-2,2'-methylenedioxy-1,1'-binaphthyl (R)-4 This intermediate was prepared by the same procedure as that used for (S)-4 from (R)-3. The spectral data are the same as those for (S)-4. Mp: 210-212 o C. Anal Calcd for C 21 H 13 I 2 : C, 59.45, H, 3.09; found: C, 59.19, H, 2.93. HRMS (ESI) calcd for C 21 H 13 I 2 Na + : 446.9858, found: 446.9857. Figure S5. Left: CD spectra of intermediates (S)-3 and (R)-3 (8 µm in hexane); Right: CD spectra of intermediates (S)-4 and (R)-4 (8 µm in hexane). S S (S,S)-1,2-Bis[2-methyl-5-(2,2'-methylenedioxy-1,1'-binaphthyl-3-yl)-3-thienyl] cyclopentene (S,S)-1 To a solution of 2 (164 mg, 0.5 mmol) in anhydrous THF (10 ml) was added n-buli (0.65 ml, 1.6 M in hexane, 1 mmol) dropwise, and the mixture was stirred at room temperature for 1h. Then B(Bu) 3 (345 mg, 1.5 mmol) was added and stirred at room temperature for another 1h followed by addition of (S)-4 (425 mg, 1 mmol), 20% Na 2 C 3 (8 ml) aqueous solution and Pd(PPh 3 ) 4 (35 mg, 0.03 mmol). The reaction SI6
mixture was heated and stirred for 10 h. After the mixture was cooled to room temperature, the organic layer was separated and the water layer was extracted with ethyl acetate (2 10 ml). The combined organic layers were washed dried over Na 2 S 4 and concentrated. The crude product was purified by flash column chromatography over silica gel to give the product as off-white solid (344 mg, 81%). Mp: 202-204 o C. 1 H NMR (CDCl 3, 400 MHz) δ = 8.16 (s, 2H), 7.94 (d, J = 8.8 Hz, 2H), 7.93 (d, J = 8.0 Hz, 2H), 7.50 (d, J = 8.8 Hz, 2H), 7.47-7.43 (m, 2H), 7.41-7.35 (m, 8H), 7.32-7.28 (m, 2H), 7.24-7.20 (m, 2H), 5.59 (d, J = 3.6 Hz, 2H), 5.56 (d, J = 3.2 Hz, 2H), 2.92-2.90 (m, 4H), 2.15-2.11 (m, 2H), 2.13 (s, 6H). 13 C NMR (CDCl 3, 50 MHz) δ = 151.2, 147.6, 136.3, 136.0, 134.9, 134.1, 132.2, 131.7, 131.6, 131.1, 130.3, 128.4, 127.8, 127.4, 127.2, 126.9, 126.7, 126.2, 126.1, 125.8, 125.5, 125.0, 120.8, 102.4, 38.4, 23.1, 14.3. Anal Calcd for C 57 H 40 4 S 2 : C, 80.25, H, 4.73; found: C, 80.27, H, 5.01. HRMS (ESI) calcd for C 57 H 40 4 S 2 Na + : 875.2266, found: 875.2241. S S (R,R)-1,2-Bis[2-methyl-5-(2,2'-methylenedioxy-1,1'-binaphthyl-3-yl)-3-thienyl] cyclopentene (R,R)-1 This compound was prepared by the same procedure as that used for (S,S)-1 from (R)-4. The spectral data are the same as those for (S,S)-1. Mp: 201-203 o C. Anal Calcd SI7
for C 57 H 40 4 S 2 : C, 80.25, H, 4.73; found: C, 79.99, H, 5.01.. HRMS (ESI) calcd for C 57 H 40 4 S 2 Na + : 875.2266, found: 875.2251. 3. Conformation analysis of (S,S)-1 pen form θ~49 o Closed form θ~55 o Figure S6. ptimized structures and dihedral angels (θ) of (S,S)-1 at open form and closed form (Chem 3D, MM2 minimize energy, ball-stick model). 4. Photoisomerization and spectra data of (S,S)-1 in organic solvent SI8
Figure S7. 1 H NMR changes of light-driven chiral switch (S,S)-1 in THF-d 8 upon UV irradiation at 310 nm for different time. Absorbance 1.2 1 0.8 0.6 0.4 0.2 Initial 5 s 15 s 25 s 40 s 60 s, PSS-UV A 0 250 450 650 Wavelength (nm) PSS-UV 2 min B 5 min 7 min 10 min 15 min, PSS-Vis 250 450 650 Wavelength (nm) Figure S8. UV-vis spectra changes of light-driven chiral switch (S,S)-1 (10 µm in hexane) upon UV irradiation at 310 nm (left) and upon visible light irradiation at 550 nm from PSS 310nm (right). Figure S9. Plot of absorbance at 550 nm of light-driven chiral switch (S,S)-1 in THF (20 µm) at room temperature: upon irradiation at 310 nm (left), then upon irradiation at 550 nm (right). 0.3 Absorbance 0.2 0.1 Absorbance 0.2 0.1 0 0 1 2 3 4 5 6 7 Cycles 0 0 1 2 3 4 5 6 7 8 Time (days) Figure S10. Left: Cyclical absorbance of light-driven chiral switch (S,S)-1 (10 µm in hexane) at 553 nm as the solution was repeatedly irradiated with UV light (310 nm) SI9
for 1 min and then with visible light (550 nm) for 15 min. Right: Thermal stability of (S,S)-1 in dark at room temperature monitored by UV absorbance of 553 nm at PSS 310nm. 5. Microscopic textures and pitch changes induced by photoisomerization of (S,S)-1 in nematic liquid crystals Figure S11. Crossed polarized optical texture of 0.5 wt% (A and B) and 1.5 wt% (C and D) (S,S)-1 in E7 before (A and C) and after (B and D) UV irradiation at 310 nm. Figure S12. Change of distance (R) between Cano s lines of 1.0 wt% (S,S)-1 in E7 upon irradiation at 310 nm and visible light irradiation at 550 nm. 6. Measurement of pitch and helical twisting power A conventional technique for pitch measurement is Grandjean-Cano wedge method 4. Such wedge cell with an opening angle θ is made by applying two differently sized SI10
spacers at each end of the cell (Figure S13). If the alignment of the substrates is planar (the director lies parallel to the surface) and the rubbing directions of the substrates are parallel to one another, the cholesteric LC becones discrete. Because the value of the pitch is fixed, and the alignment is also fixed, the cholesteric LC arranges itself as in Figure S11. This arrangement produces disclination lines between areas that contain a different number of layers. The difference in thickness between each domain must be p/2 in order to satisfy the alignment boundary condition. The disclination lines of the cholesteric liquid crystal in the wedge cell can be seen through a polarizing optical microscope. The pitch was determined according to the equaton p=2r tanθ, where R represents the distance between the Grandjean lines and θ is the wedge angle of wedge cells (EHC, KCRK-07, tanθ = 0.0196). The inverse of pitch proportionally increases with increase in the concentration of a chiral dopant and HTP values is β = 1/(pc), where β is the helical twisting power, i.e, the ability of the chiral dopant to twist a nematic LC, and is the concentration of the chiral dopant. Figure S13. Schematic illustation of a Grandjean-Cano wedge cell for the pitch measurement of cholesteric LC. Disclination lines are pointed out with arrows and the thickness change between two domains is marked as p/2. The chiral nematic liquid crystal was prepared by weighing appropriate amount of host liquid crystal and the dopant into a vial followed by mixing them with the SI11
addition of a few drops of dichloromethane. After evaporation of the solvent under reduced pressure, the mixture was loaded into the wedge cell by capillary action at room temperature. The pitch was then determined by measuring the intervals of Cano s lines appearing on the surfaces of wedge-type liquid crystalline cells. Three different concentrations were used by this method for each sample, and the HTP were determined by plotting 1/p (µm -1 ) against concentration of the dopant c (mol%) according to the equation β = 1/(pc). Figure S14. Reciprocal helical pitch as a function of concentration of (S,S)-1 in nematic LC E7. 7. Reference: 1. (a) Lucas, L. N.; de Jong, J. J. D.; van Esch, J. H.; Kellogg, R. M.; Feringa, B. L. Eur. J. rg. Chem. 2003, 155-166. (b) Akazawa, M.; Uchida, K.; de Jong, J. J. D.; Areephong, J.; Stuart, M.; Carili, G.; Browne, W. R.; Feringa, B. L. rg. Biomol. Chem. 2008, 6, 1544-1547. 2. van Es, J. J. G. S.; Biemans, H. A. M.; Meijer, E. W. Tetrahedron: Asymmetry 1997, 8, 1825-1831. 3. Simpson, J. E.; Daub, G. H.; Hayes, F. N. J. rg. Chem. 1973, 38, 1771. SI12
4. (a) Grandjean, F. C. R. Hebd. Seances Acad. Sci. 1921, 172, 71-74. (b) Cano, R. Bull. Soc. Fr. Mineral. 1968, 91, 20-27. (c) Heppke, G.; estreicher, F. Mol. Cryst. Liq. Cryst. 1978, 41, 245-249. SI13
8. Copies of 1 H NMR and 13 C NMR 1 H NMR of intermediate 3: SI14
13 C NMR of intermediate 3: SI15
1 H NMR of intermediate 4: SI16
13 C NMR of intermediate 4: SI17
1 H NMR of (S, S)-1: SI18
13 C NMR of (S,S)-1: SI19