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1 Electronic Supplementary Material (ESI) for ChemComm. This journal is The Royal Society of Chemistry 24 Supporting Information Chiral BINOL-Bridged Imidazole Dimer Possessing Sub-Millisecond Fast Photochromism Takahiro Iwasaki a, Tetsuya Kato a, Yoichi Kobayashi a and Jiro Abe *ab a Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-- Fuchinobe, Chuo-ku, Sagamihara, Kanagawa , Japan b CREST, Japan Science and Technology Agency (JST), K s Gobancho, 7 Gobancho, Chiyoda-ku, Tokyo 2-7, Japan. jiro_abe@chem.aoyama.ac.jp Table of contents Synthesis...S2. Synthesis of.2 Synthesis of 2 (racemate).3 Synthesis of (S)-2 2. HR-ESI-TOF-MS.... S25 3 HPLC analyses for determination of purity..s2 4 Chiral HPLC analyses for determination of enantiomeric excesses (ee).s27 5 X-ray crystallographic analysis.s28 Laser flash photolysis S3 7 Eyring plot...s3 8 CD spectroscopy...s32 9 UV-vis absorption spectroscopy and investigation for fatigue resistance..s32 DFT calculations S34 References S72 S

2 . Synthesis All reactions were monitored by thin-layer chromatography carried out on.2 mm E. Merck silica gel plates (F-254). Column chromatography was performed on the silica gel (Silica Gel N (spherical, neutral), 4-5 μm, Kanto Chemical Co., Inc.). H-NMR spectra and 3 C-NMR spectra were recorded on a Bruker AVANCE III 4 NanoBay. DMSO-d, CDCl3 and CD2Cl2 were used as deuterated solvent. MASS spectra (ESI-TOF-MS) were measured by using a Bruker microtof II- AGA. All reagents were purchased from Tokyo Chemical Industry Co., Ltd., Wako Pure Chemical Industries, Ltd., and Aldrich Chemical Company, Inc. and were used without further purification. All reaction solvents were distilled on the appropriate drying reagents prior to use.. Synthesis of Scheme S. Synthetic procedure of. S2

3 Compound 3, -Bi-2-naphthol (2. g,.99 mmol), 4-fluorobenzaldehyde (.8 ml, 7. mmol) and potassium carbonate (2.42 g, 7.5 mmol) were stirred at C in DMF (5 ml). After 42 h, the reaction mixture was cooled to room temperature and the target compound was extracted with CH2Cl2. The organic phase was washed with water, dried, and evaporated. The residue was purified by column chromatography over silica gel with CHCl3 as eluent to give a light yellow solid (.28 g, 2.58 mmol, yield; 37 %). H NMR (4 MHz, DMSO-d) : δ 9.79 (s, 2H), 8.3 (d, J = 9. Hz, 2H), 8.4 (d, J = 8.2 Hz, 2H), 7.9 (d, J = 8. Hz, 4H), 7.5 (t, J = 7., 9. Hz, 2H), (m, 4H), 7.7 (d, J = 8.2 Hz, 2H),.92 (d, J = 8. Hz, 4H). HR-MS (ESI+) calculated for C34H23O4 [M+H] , found Figure S. H NMR spectrum of 3 in DMSO-d. S3

4 Compound 4 Compound 3 (5 mg,.33 mmol), benzil (22 mg,.5 mmol), and ammonium acetate (35mg, 4.54 mmol) were stirred at C in CH2Cl2 (. ml) in a sealed tube. After 4 h, the reaction mixture was cooled to room temperature and washed with water, followed by ethanol. The precipitate was filtered and washed with hexane to give a white powder (94 mg,.222 mmol, yield; 73 %). H NMR (4 MHz, DMSO-d) δ: 2.5 (s, 2H), 8. (d, J = 8.7 Hz, 2H), 8.4 (d, J = 7.8, 2H), 7.94 (d, J = 7.8 Hz, 4H), (m, 28H),.93 (d, J = 7.8 Hz, 4H); 3 C NMR ( MHz, DMSO-d) δ: 5.9, 5.59, 45., 3.88, 35.5, 33.48, 3.4, 3.2, 28.47, 28.25, 28.2, 27.8, 27.54, 2.97, 2., 2.34, 25.35, 25., 24.98, 2.5, 9.35, 8.5; HR-MS (ESI+) calculated for C2H43N4O2 [M+H] , found S4

5 Figure S2. H NMR spectrum of 4 in DMSO-d. Figure S3. 3 C NMR spectrum of 4 in DMSO-d. S5

6 Compound All manipulations were carried out with the exclusion of light. Under nitrogen, a solution of potassium ferricyanide (.8 g, 35.8 mmol) and potassium hydroxide (4.5 g, 72.2 mmol) in water (2 ml) was added to a solution of compound 4 (29 mg,.78 mmol) in benzene (2 ml). The reaction mixture was vigorously stirred at room temperature for 2 h. The organic layer was washed with water, dried, and evaporated. The residue was purified by column chromatography over silica gel with AcOEt/hexane = /3 as eluent and followed by recrystallization from CHCl3/hexane to give a slightly green crystal of 3 (29 mg,.48 mmol, yield; 2 %). H NMR (4 MHz, CD2Cl2) δ: 8.3 (d, J = 8.9 Hz, H), (m, 3H), (m, 32H),.93 (d, J = 8.8 Hz, H),.75 (d, J = 8.2 Hz, H),. (d, J = 8.7 Hz, H),.4 (d, J = 8.4 Hz, H),. (d, J = 8.5 Hz, H), 5.94 (d, J = 8.8 Hz, H); 3 C NMR ( MHz, CD2Cl2) δ:.82,.34,.9, 58.9, 5.23, 49.92, 48.39, 38.4, 35.2, 35.23, 35.7, 34.75, 33.5, 33.39, 32.37, 32.34, 32.2, 3.89, 3.85, 3.3, 3.32, 3.27, 3., 3.77, 3.38, 3.24, 29.9, 29.83, 29.74, 28.92, 28.82, 28.7, 28., 28.4, 28.42, 28.27, 28.9, 28.4, 27.45, 27.33, 27.27, 2.53, 2.2, 2.3, 24.93, 24.34, 23.5, 22.47,.59, 5.8, 3.98, 3.7; HR-MS (ESI+) calculated for C2H4N4O2 [M+H] , found S

7 Figure S4. H NMR spectrum of in CD2Cl2. * * * Figure S5. 3 C NMR spectrum of in CD2Cl2 (*Solvent Peaks). S7

8 .2 Synthesis of 2 (racemate) Scheme S2. Synthetic procedure of 2. S8

9 Compound 5 (R)-, -Bi-2-naphthol (2. g,.99 mmol), 2-chloro-4-fluorobenzaldehyde (2. g, 2.85 mmol) and potassium carbonate (2.5 g, 5.85 mmol) were stirred at C in DMF (5 ml). After 5 h, the reaction mixture was cooled to room temperature and the target compound was extracted with CH2Cl2. The organic phase was washed with water. The organic phase was dried over anhydrous sodium sulfate, filtered, and evaporated to give a yellow solid. The yellow solid was purified by column chromatography over silica gel with CH2Cl2 as eluent to give a white amorphous solid (2.8 g, yield; 72 %). H NMR (4 MHz, DMSO-d) δ 8.9 (d, J = 9.2 Hz, 2H), 8.9 (d, J = 8. Hz, 2H), 7. (d, J = 8. Hz, 2H), 7.54 (dd, J = 7.3, 7.9 Hz, 2H), 7.48 (d, J = 9.2 Hz, 2H), 7.4 (dd, J = 8., 9.2 Hz, 2H), 7.2 (d, J = 8. Hz, 2H),.83 (dd, J = 9.2, 2.4 Hz, 2H),.77 (d, J = 2.4 Hz, 2H); HR-MS (ESI+) calculated for C34H2Cl2O4 [M+H] , found * * Figure S. H NMR spectrum of 5 in DMSO-d (*Solvent Peaks). S9

10 Compound Compound 5 (287 mg,.5 mmol), benzil (324 mg,.54 mmol) and ammonium acetate (599 mg, 7.77 mmol) were stirred at C in CH2Cl2 (.7 ml) in a sealed tube. After 2 days, the reaction mixture was cooled to room temperature and washed with water, followed by ethanol. The precipitate was filtered and washed with hexane to give a white powder (374 mg,.27 mmol, yield; 77.8 %). H NMR (4 MHz, DMSO-d) δ 2.5 (s, 2H), 8.8 (d, J = 9.2 Hz, 2H), 8.8 (d, J = 7.9 Hz, 2H), 7.9 (d, J = 8. Hz, 2H), (m, 28H), 7.5 (d, J = 2.4 Hz, 2H),.98 (dd, J = 9.2, 2.4 Hz, 2H); HR-MS (ESI+) calculated for C2H4Cl2N4O2 [M+H] , found * * Figure S7. H NMR spectrum of in DMSO-d (*Solvent Peaks). S

11 Compound 2 All manipulations were carried out with the exclusion of light. Under nitrogen, a solution of potassium ferricyanide (5.9 g, 8. mmol) and potassium hydroxide (2.5 g, 3. mmol) in water (25 ml) was added to a solution of compound (344 mg,.33 mmol) in benzene (25 ml). The reaction mixture was vigorously stirred at room temperature for 3 h. The organic layer was washed with water, dried, and evaporated. The residue was purified by column chromatography over silica gel with AcOEt/hexane = /3 as eluent to give a yellow solid (29 mg, yield; %). The obtained compound was the racemate as was shown in Figure S27 because the refluxes at > C racemize the (R)-, -bi- 2-naphthol moiety. H NMR (4 MHz, DMSO-d) δ 8.3 (d, J = 9.2 Hz, H), 8.8 (m, 3H), (m, 32H),.9 (dd, J = 9.2, 2.4 Hz, 2H), 5.97 (dd, J = 9.2, 2.4 Hz, 2H); HR-MS (ESI+) calculated for C2H39Cl2N4O2 [M+H] , found * * * * Figure S8. H NMR spectrum of 2 in DMSO-d (*Solvent Peaks). S

12 .3 Synthesis of (S)-2 Scheme S3. Synthetic procedure of (S)-2 (the synthesis of (R)-2 was the identical to that of (S)-2 except that (R)-, -bi-2-naphthol was used as the starting material). S2

13 Compound (S)-7 Trityl chloride (3.89 g 3.9 mmol) in CH2Cl2 (45 ml) were added to (S)-,-bi-2-naphthol (4. g, 3.9 mmol), triethylamine (2.32 ml,.7 mmol) and CH2Cl2 (45 ml) at C. The mixture was allowed to warm to room temperature and was stirred for 2 h. The reaction mixture was washed with water. The organic phase was dried over anhydrous sodium sulfate, and the solution was filtered. The evaporation of the solvent afforded a yellow solid and the recrystallization from CH2Cl2/hexane gives a white crystal of compound (S)-7 (5.8 g, yield; 8.7 %). H NMR (4 MHz, DMSO-d) δ 9.5 (s, H), 7.94 (d, J = 8.9 Hz, H), 7.89 (dd, J =.3, 2.4 Hz, H), 7.74 (d, J = 8. Hz, H), 7.49 (d, J = 9.2 Hz, H), 7.43 (d, J = 8.9 Hz, H), (m, 9H), 7. (d, J = 8.3 Hz, H),.8 (dd, J =.3, 2.4 Hz, H),.73 (d, J = 8.9 Hz, H); 3 C NMR ( MHz, CDCl3) δ 52.99, 5., 4.9, 43.99, 34.7, 33.82, 3.49, 29.4, 29.3, 29.23, 28.77, 28.39, 28.7, 27.99, 27.98, 27.73, 27.54, 27.3, 27.2, 2.97, 2.34, 25.32, 25.8, 24.4, 24.2, 24.9, 8.4, 7.82, 7.5, 5.89, 9.; HR-MS (ESI ) calculated for C39H27O2 [M H] 527.2, found S3

14 * Figure S9. H NMR spectrum of (S)-7 in DMSO-d (*Solvent Peak). Figure S. 3 C NMR spectrum of (S)-7 in CDCl3. S4

15 Compound (S)-8 Compound (S)-7 (2. g, 3.78 mmol), 2-chloro-4-fluorobenzaldehyde (78 mg, 4.92 mmol) and potassium carbonate (.3 g, 9.84 mmol) were stirred at C in DMF (5 ml). After 23 h, the reaction mixture was cooled to room temperature and the target compound was extracted with AcOEt. The organic phase was washed with water. The organic phase was dried over anhydrous sodium sulfate, filtered, and evaporated to give a yellow oil solid. The yellow oil solid was purified by column chromatography over silica gel with CH2Cl2/hexane as eluent to give a white amorphous solid (.54 g, yield;. %). H NMR (4 MHz, DMSO-d) δ.8 (s, H), 8.28 (d, J = 9. Hz, H), 8.5 (d, J = 8. Hz, H), 7.7 (dd, J = 7.,.4 Hz, H), (m, 5H), (m, 23H),.94 (d, J = 2.3 Hz, H),.89 (dd, J = 8., 2.2 Hz, H),.7 (d, J = 9.2 Hz, H); 3 C NMR ( MHz, CDCl3) δ 88.47, 3., 5.93, 5.2, 44.7, 39.28, 34.29, 33.5, 3.58, 3.74, 29.79, 28.42, 28., 27.9, 27.88, 27.8, 2.8, 2.77, 2.5, 2., 2.5, 25.8, 24.93, 23., 2.29, 9.7, 9.32, 8.5,., 89.4, 53.4; HR-MS (ESI+) calculated for C4H3ClNaO3 [M+Na] , found S5

16 * Figure S. H NMR spectrum of (S)-8 in DMSO-d (*Solvent Peak). Figure S2. 3 C NMR spectrum of (S)-8 in CDCl3. S

17 Compound (S)-9 TFA (9.7 ml) was added to compound (S)-8 (.8 g,.2 mmol) in CH2Cl2 (2 ml) at C. The mixture was allowed to warm to room temperature and was stirred for 2 h, quenched with NaHCO3 aqueous. The organic phase was washed with water, dried over anhydrous sodium sulfate, filtered, and evaporated to give a brown oil solid. The brown oil solid was purified by column chromatography over silica gel with CH2Cl2/hexane as eluent to give a white amorphous solid (544 mg, yield; 79.2 %). H NMR (4 MHz, DMSO-d) δ.3 (s, H), 9. (s, H), 8.7 (d, J = 8.9 Hz, H), 8.9 (d, J = 8.2 Hz, H), (m, 2H), 7.9 (d, J = 8.7 Hz, H), (m, H), 7.47 (d, J = 8.9 Hz, H), (m, H), (m, 3H), 7.5 (d, J = 8.4 Hz, H),.97.9 (m, 3H); 3 C NMR ( MHz, DMSO-d) δ 88.24, 2.7, 53.4, 5., 37.58, 33., 33.54, 3.24, 3.8, 3.2, 29., 28.27, 27.98, 27.73, 27.49, 2.88, 2., 25.55, 25.4, 23.87, 22.53, 2.7, 8.29, 8.,.54, 2.98; HR-MS (ESI ) calculated for C27HClO3 [M H] , found S7

18 * * Figure S3. H NMR spectrum of (S)-9 in DMSO-d (*Solvent Peaks). Figure S4. 3 C NMR spectrum of (S)-9 in DMSO-d. S8

19 Compound (S)-5 Compound (S)-9 (87 mg,.9 mmol), 2-chloro-4-fluorobenzaldehyde (45 mg, 2.85 mmol) and potassium carbonate (88 mg, 5.85 mmol) were stirred at C in DMF (5 ml). After 8 h, the reaction mixture was cooled to room temperature and the target compound was extracted with AcOEt. The organic phase was washed with water. The organic phase was dried over anhydrous sodium sulfate, filtered, and evaporated to give a yellow solid. The yellow solid was purified by column chromatography over silica gel with CH2Cl2/hexane as eluent to give a white amorphous solid (855 mg, yield; 79.9 %). H NMR (4 MHz, DMSO-d) δ 8.9 (d, J = 9.2 Hz, 2H), 8.9 (d, J = 8. Hz, 2H), 7. (d, J = 8. Hz, 2H), 7.54 (dd, J = 7.3, 7.9 Hz, 2H), 7.48 (d, J = 9.2 Hz, 2H), 7.4 (dd, J = 8., 9.2 Hz, 2H), 7.2 (d, J = 8. Hz, 2H),.83 (dd, J = 9.2, 2.4 Hz, 2H),.77 (d, J = 2.4 Hz, 2H); 3 C NMR ( MHz, DMSO-d) δ 88.23, 2.7, 53.3, 5., 47.73, 37.58, 33., 33.54, 3.24, 3.8, 3.2, 29.59, 28.27, 27.97, 27.7, 27.48, 2.88, 2., 2.47, 2.32, 25.59, 25.55, 25.4, 23.87, 22.53, 2.7, 8.29, 8.,.54, 2.98; HR-MS (ESI+) calculated for C34H2Cl2O4 [M+H] , found S9

20 * * Figure S5. H NMR spectrum of (S)-5 in DMSO-d (*Solvent Peaks). Figure S. 3 C NMR spectrum of (S)-5 in DMSO-d. S2

21 Compound (S)- Compound (S)-5 (287 mg,.5 mmol), benzil (324 mg,.54 mmol) and ammonium acetate (599 mg, 7.77 mmol) were stirred at C in CH2Cl2 (.7 ml) in a sealed tube. After 2 days, the reaction mixture was cooled to room temperature and washed with water, followed by ethanol. The precipitate was filtered and washed with hexane to give a white powder (374 mg,.27 mmol, yield; 77.8 %). H NMR (4 MHz, DMSO-d) δ 2.5 (s, 2H), 8.8 (d, J = 9.2 Hz, 2H), 8.8 (d, J = 7.9 Hz, 2H), 7.9 (d, J = 8. Hz, 2H), (m, 28H), 7.5 (d, J = 2.4 Hz, 2H),.98 (dd, J = 9.2, 2.4 Hz, 2H); 3 C NMR ( MHz, CDCl3) δ 58.3, 5.8, 42.92, 37.5, 34.5, 34.2, 3.2, 3.9, 3.7, 3.37, 29.97, 28.9, 28.28, 28.24, 27.8, 27.72, 27.55, 27.2, 27.5, 2.95, 25.79, 25.42, 22.73, 22.28, 9.9, 8.83, 7.4; HR-MS (ESI+) calculated for C2H4Cl2N4O2 [M+H] , found S2

22 * * * * Figure S7. H NMR spectrum of (S)- in DMSO-d (*Solvent Peaks). Figure S8. 3 C NMR spectrum of (S)- in CDCl3. S22

23 Compound (S)-2 All manipulations were carried out with the exclusion of light. Under nitrogen, a solution of potassium ferricyanide (3.78 g,.5 mmol) and potassium hydroxide (.3 g, 24.2 mmol) in water ( ml) was added to a solution of compound (S)- (22 mg,.24 mmol) in benzene ( ml). The reaction mixture was vigorously stirred at room temperature for 3 h. The organic layer was washed with water, dried, and evaporated. The residue was purified by column chromatography over silica gel with AcOEt/hexane = /3 as eluent to give a yellow solid (. mg, yield; 3 %). H NMR (4 MHz, DMSO-d) δ 8.3 (d, J = 9.2 Hz, H), 8.8 (m, 3H), (m, 32H),.9 (dd, J = 9.2, 2.4 Hz, 2H), 5.97 (dd, J = 9.2, 2.4 Hz, 2H); 3 C NMR ( MHz, CDCl3) δ 7.35, 5.,.3,.5, 49.42, 49.42, 49.5, 44.95, 37.44, 3.34, 35., 34.87, 34.8, 34.28, 33.2, 33.5, 32.9, 3.78, 3.2, 3.5, 3.38, 3.3, 3.84, 3.4, 3.5, 3.27, 3., 29.94, 29.35, 28.97, 28.48, 28.3, 28.2, 28., 28.7, 27.7, 27.3, 27.2, 27., 2.88, 2.28, 2.3, 25.99, 25.85, 25.8, 23.82, 22.48, 2.84, 2.2,.9, 2.52, 2.9,.8; HR-MS (ESI+) calculated for C2H39Cl2N4O2 [M+H] , found S23

24 * * * * Figure S9. H NMR spectrum of (S)-2 in DMSO-d (*Solvent Peaks). Figure S2. 3 C NMR spectrum of (S)-2 in CDCl3. S24

25 2. HR-ESI-TOF-MS-spectra Error.5 ppm Figure S2. HR-ESI-TOF-MS of. Error 3. ppm Figure S22. HR-ESI-TOF-MS of 2. S25

26 Error. ppm Figure S23. HR-ESI-TOF-MS of (S) HPLC analyses for determination of purity HPLC analyses using THF/CH3CN = /5 as an eluent was performed with system composed of a Mightysil RP8 (4. mm 25 cm) column and JASCO PU-28 Plus pump equipped with a UV-275 Plus UV/VIS detector. The mobile phase was THF/CH3CN = /5 with a flow rate of. ml/min, inject volume; 2. μl. Figure S24. HPLC chromatogram of the racemate of (left) and 2 (right), detection wavelength; 254 nm, purity 99%, respectively. S2

27 Figure S25. HPLC chromatograms of (R)-2, detection wavelength; 254 (left) and 34 nm (right), purity 99%. Figure S2. HPLC chromatograms of (S)-2, detection wavelength; 254 (left) and 34 nm (right), purity 99%. 4. Chiral HPLC analyses for determination of enantiomeric excesses (ee) HPLC analyses using CH2Cl2/hexane = / as an eluent was performed with a system composed of a DAICEL CHIRALPAK IC column (4. mm 25 cm) and JASCO PU-28 Plus pump equipped with a UV-275 Plus UV/VIS detector. Figure S27. HPLC charts of 2, (R)-2 and (S)-2. S27

28 5. X-ray crystallographic analysis The diffraction data of the single crystal of are collected on the Bruker APEX II CCD area detector (MoKα, λ =.773 nm). During the data collection, the lead glass doors of the diffractometer were covered to exclude the room light. The data refinement was carried out by the Bruker APEX II software package with SHELXT program. S) All non-hydrogen atoms were anisotropically refined. Figure S28. ORTEP representation of the molecular structure of with thermal ellipsoid at 5% probability. The hydrogen atoms and solvent molecules are omitted. Oxygen and nitrogen atoms are highlighted in red and blue, respectively. S28

29 Table S. X-ray crystallographic data of. Identification code Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions C2 H4 N4 O K.773 Å Triclinic P- a =.8574(5) Å α= 9.(2). b = 4.598(2) Å β= 5.5(2). c = 5.54(2) Å γ =.4(2). Volume Z Density (calculated) Absorption coefficient F() (5) Å3 2.3 Mg/m3.79 mm- 92 Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Completeness to theta = 2.4 Absorption correction Refinement method Data / restraints / parameters Goodness-of-fit on F2 Final R indices [I>2sigma(I)].4 x.35 x. mm3.5 to <=h<=, -8<=k<=2, -<=l<= [R(int) =.37] 9.4 % Empirical Full-matrix least-squares on F2 883 / / 3 Goodness-of-fit on F2.23 R =.55, wr2 =.5 R indices (all data) R indices (all data) R =.79, wr2 =.23 Largest diff. peak and hole.59 and -.27 e.å-3 S29

30 . Laser flash photolysis The laser flash photolysis experiments were performed with a Unisoku TSP- time-resolved spectrophotometer. A Hz Q-switch Nd:YAG laser (Continuum Minilite II) with the third harmonic at 355 nm (ca. 4 mj per 5 ns pulse) was employed for the excitation light. A halogen lamp (OSRAM HLX423) was used for a probe light and the transmitted light through the sample was guided into the monochrometer and a detector (Unisoku MD2 and Hamamatsu R2949 photomultiplier tube, respectively) with an optical fiber scope. 7. Eyring plots To obtain the activation parameters of the thermal back reactions of R and 2R, we conducted the temperature dependence of the decay profiles of the thermal back reactions of R and 2R. The rate constants for the thermal back reaction for R and 2R are tabulated in Table S2 and S3, respectively. These temperature dependences were analyzed by Eyring plots and these plots are shown in Figure S28 for R and Figure S29 for 2R, respectively. Table S2. First-order rate constants for the thermal back-reaction of in degassed benzene (2. 5 M ) at different temperature. T / k / s S3

31 Figure S29. The Eyring plot for the thermal back-reaction of colored species of in degassed benzene (2. 5 M ). Table S3. First-order rate constants for the thermal back-reaction of 2 in degassed benzene (2.3 5 M) at different temperature. T / C k / s S3

32 Figure S3. The Eyring plot for the thermal back-reaction of colored species of 2 in degassed benzene (2.3 5 M). 8. CD spectroscopy Circular dichroism (CD) spectra were recorded on a JASCO J-82 spectropolarimeter. The CD spectra of (R)-2 and (S)-2 in acetonitrile (3.3 5 M) were measured with a -mm quartz cell at room temperature. Photoracemization processes of (R)-2 and (S)-2 were analyzed using a Q-switch Nd:YAG laser (Continuum Minilite II) with the third harmonic at 355 nm (ca. 4 mj per 5 ns pulse) as the excitation beam. 9. UV-vis absorption spectroscopy and investigation for fatigue resistance UV-vis absorption spectra were recorded on a Shimadzu UV-35 spectrometer. The UV-vis absorption spectra of (2. 5 M) and 2 (2.3 5 M) in benzene were measured with a -mm quartz cell at 25 C. The fatigue resistances of and 2 were measured using a Q-switch Nd:YAG laser (Continuum Minilite II) with the third harmonic at 355 nm (ca. 4 mj per 5 ns pulse) as the excitation beam. S32

33 Figure S3. UV-vis absorption spectra of (2. 5 M) (left) and 2 (2.3 5 M) (right) in benzene before and after laser shots at 25 C.. DFT calculations All calculations were carried out using the Gaussian 9 program (Revision D.) S2). The molecular structures were fully optimized at the M2X/-3G(d) level of the theory for 2 and the UM2X/- 3G(d) level of the theory for 2R. The analytical second derivatives were computed using the vibrational analysis to confirm each stationary point to be a minimum. The TDDFT calculations were performed at the MPWPW9/-3+G(d) level of the theory for 2 and UMPWPW9/-3+G(d) level of the theory for 2R for the optimized structures. Center Number Table S4. Standard orientation of the optimized geometry for 2. Atomic Atomic Coordinates (Angstroms) Number Type X Y Z S33

34 S34

35 S35

36 S3

37 Figure S32. Optimized structure of 2. SCF Done: E(RM2X) = A.U. Zero-point correction =.8473 (Hartree/Particle) Thermal correction to Energy = Thermal correction to Enthalpy = Thermal correction to Gibbs Free Energy =.75 Sum of electronic and zero-point Energies = Sum of electronic and thermal Energies = Sum of electronic and thermal Enthalpies = Sum of electronic and thermal Free Energies = Low frequencies Low frequencies The Result for the TDDFT calculation for 2 Excitation energies and oscillator strengths: Excited State : Singlet-A ev nm f=.48 <S**2>= > This state for optimization and/or second-order correction. Total Energy, E(TD-HF/TD-KS) = Copying the excited state density for this state as the -particle RhoCI density. Excited State 2: Singlet-A 3.33 ev nm f=.48 <S**2>= > S37

38 243 -> Excited State 3: Singlet-A 3.5 ev nm f=.44 <S**2>= > > > Excited State 4: Singlet-A ev nm f=.24 <S**2>= > > > Excited State 5: Singlet-A ev nm f=.5 <S**2>= > > > > > > > > Excited State : Singlet-A ev nm f=.25 <S**2>= > > Excited State 7: Singlet-A ev 32.9 nm f=.4 <S**2>=. 24 -> > Excited State 8: Singlet-A 3.88 ev 39.5 nm f=.5 <S**2>= > > > S38

39 Excited State 9: Singlet-A ev nm f=.23 <S**2>= > > > > > > Excited State : Singlet-A ev nm f=. <S**2>= > > > Excited State : Singlet-A ev 3.7 nm f=.2 <S**2>= > > > > > > > > > Excited State 2: Singlet-A ev 3.7 nm f=.225 <S**2>= > > > > > Excited State 3: Singlet-A 4.24 ev 3.4 nm f=.3 <S**2>= > S39

40 242 -> > Excited State 4: Singlet-A 4.38 ev 3.5 nm f=.94 <S**2>= > > > > > > > > > Excited State 5: Singlet-A ev nm f=.8 <S**2>= > > Excited State : Singlet-A 4.93 ev nm f=.99 <S**2>=. 24 -> > > > > Excited State 7: Singlet-A ev 294. nm f=.54 <S**2>= > > > Excited State 8: Singlet-A ev nm f=.9 <S**2>= > > > S4

41 232 -> > > > Excited State 9: Singlet-A ev nm f=. <S**2>=. 23 -> > > > > > Excited State 2: Singlet-A ev nm f=.7 <S**2>= > > > > > > Excited State 2: Singlet-A ev nm f=.5 <S**2>= > > > > > > > Excited State 22: Singlet-A 4.37 ev nm f=.93 <S**2>=. 23 -> > > S4

42 233 -> Excited State 23: Singlet-A 4.43 ev 28.7 nm f=.93 <S**2>= > > > > > > > Excited State 24: Singlet-A ev 28.2 nm f=.593 <S**2>= > > > > Excited State 25: Singlet-A ev nm f=.285 <S**2>=. 24 -> > > > > > Excited State 2: Singlet-A ev nm f=.548 <S**2>=. 24 -> > > Excited State 27: Singlet-A ev 27.5 nm f=.285 <S**2>= > > > S42

43 234 -> > > Excited State 28: Singlet-A ev nm f=.83 <S**2>=. 23 -> > > > > > > > Excited State 29: Singlet-A ev nm f=.8 <S**2>= > > > > > > > > > > > > > Excited State 3: Singlet-A ev nm f=.8 <S**2>= > > > > S43

44 23 -> > > > Excited State 3: Singlet-A ev nm f=.8 <S**2>= > > > > > Excited State 32: Singlet-A ev 272. nm f=.92 <S**2>= > > > > > > > > > Excited State 33: Singlet-A ev nm f=.3 <S**2>= > > > > > > > > > > S44

45 243 -> Excited State 34: Singlet-A ev nm f=.8 <S**2>= > > > Excited State 35: Singlet-A ev nm f=.25 <S**2>= > > > > > > > > > > Excited State 3: Singlet-A 4.78 ev 29.7 nm f=.94 <S**2>= > > > > Excited State 37: Singlet-A 4.79 ev 25. nm f=.52 <S**2>= > > > > > > > > S45

46 Excited State 38: Singlet-A ev 2.95 nm f=.3 <S**2>= > > > > > > > > > > Excited State 39: Singlet-A ev 2.4 nm f=.7 <S**2>= > > > > > > > > Excited State 4: Singlet-A ev nm f=.7 <S**2>= > > > > > > > S4

47 MO245 MO244 MO243 MO242 MO237 Figure S33. The relevant molecular orbitals of 2 calculated at the MPWPW9/-3+G(d)//M2X/-3G(d) level. S47

48 Center Number Table S5. Standard orientation of the optimized geometry for 2R. Atomic Atomic Coordinates (Angstroms) Number Type X Y Z S48

49 S49

50 S5

51 Figure S34. Optimized structure of 2R. SCF Done: E(UM2X) = A.U. S**2 before annihilation.837, after.535 Zero-point correction = (Hartree/Particle) Thermal correction to Energy =.892 Thermal correction to Enthalpy = Thermal correction to Gibbs Free Energy =.7524 Sum of electronic and zero-point Energies = Sum of electronic and thermal Energies = Sum of electronic and thermal Enthalpies = Sum of electronic and thermal Free Energies = Low frequencies Low frequencies The Result for the TDDFT calculation for 2R Excitation energies and oscillator strengths: S5

52 Excited State :.732-A.29 ev nm f=.24 <S**2>=.5 244A -> 245A B -> 245B.7424 This state for optimization and/or second-order correction. Total Energy, E(TD-HF/TD-KS) = Copying the excited state density for this state as the -particle RhoCI density. Excited State 2:.983-A 244A -> 245A B -> 245B ev nm f=.534 <S**2>=-.9 Excited State 3: 2.59-A 239A -> 245A A -> 245A B -> 245B B -> 245B ev 55.4 nm f=. <S**2>=.434 Excited State 4: 2.42-A 24A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B ev 27.4 nm f=.5 <S**2>=.495 Excited State 5: 2.27-A 234A -> 245A. 238A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B ev 3.99 nm f=.447 <S**2>=.978 S52

53 Excited State : 2.28-A 23A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B.88 23B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B ev nm f=.2472 <S**2>=.883 Excited State 7: A 2.3 ev nm f=.4 <S**2>= A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A -. S53

54 243A -> 245A B -> 245B.7 229B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B.242 Excited State 8: 2.42-A 228A -> 245A.39 23A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A.2 243A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B.24 24B -> 245B B -> 245B ev nm f=.59 <S**2>=.24 Excited State 9: A ev 59.5 nm f=.82 <S**2>=.38 S54

55 234A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 24A.9 234B -> 245B B -> 245B.28 24B -> 245B B -> 245B B -> 245B B -> 24B.2 Excited State : 2.75-A 239A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B ev 5.8 nm f=.4 <S**2>=.82 Excited State : 2.3-A 238A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B ev nm f=.9 <S**2>=.89 S55

56 242B -> 245B B -> 245B Excited State 2: 2.79-A 233A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B ev 49.9 nm f=.3 <S**2>=.83 Excited State 3: 2.99-A 24A -> 245A.49 24A -> 24A A -> 245A A -> 24A A -> 247A A -> 247A B -> 245B B -> 24B B -> 245B B -> 24B B -> 247B B -> 247B ev nm f=.8 <S**2>=.954 Excited State 4: 2.-A 235A -> 245A A -> 245A ev nm f=.52 <S**2>=.42 S5

57 239A -> 245A A -> 245A A -> 247A A -> 245A A -> 24A A -> 247A A -> 24A B -> 245B B -> 245B B -> 245B B -> 245B B -> 247B B -> 245B B -> 24B B -> 247B B -> 24B Excited State 5: 2.5-A 232A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B ev nm f=.23 <S**2>=.389 Excited State : 3.3-A 235A -> 245A A -> 245A A -> 245A A -> 245A A -> 247A ev nm f=.53 <S**2>=2.4 S57

58 242A -> 24A A -> 247A A -> 245A A -> 24A B -> 245B B -> 245B B -> 245B B -> 247B B -> 24B B -> 247B B -> 245B.5 243B -> 24B Excited State 7: 2.4-A 235A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 24A B -> 245B B -> 245B B -> 245B.23 24B -> 245B B -> 245B B -> 24B ev nm f=. <S**2>=.9 Excited State 8: A 23A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A ev 4.4 nm f=.32 <S**2>=. S58

59 24A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B.2552 Excited State 9: 3.4-A 23A -> 245A -. 24A -> 245A A -> 24A A -> 245A A -> 24A A -> 247A A -> 247A B -> 245B B -> 24B B -> 245B B -> 24B B -> 247B B -> 245B B -> 247B ev 45.9 nm f=. <S**2>=2.24 Excited State 2: 2.4-A 23A -> 245A A -> 245A A -> 245A A -> 245A -. 23A -> 245A A -> 245A A -> 245A A -> 245A ev nm f=.22 <S**2>=.89 S59

60 24A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B.7 23B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B -.4 Excited State 2: 2.39-A 23A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B.99 23B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B ev nm f=.7 <S**2>=.8 Excited State 22: 2.58-A 232A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A ev nm f=.2 <S**2>=.89 S

61 229B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B Excited State 23: 2.52-A 228A -> 245A.7 232A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B ev 449. nm f=.47 <S**2>=.337 Excited State 24: 2.25-A 227A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A ev nm f=. <S**2>=.33 S

62 243A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B Excited State 25: 2.47-A 22A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B ev nm f=.2 <S**2>=.27 Excited State 2: 2.5-A ev nm f=.25 <S**2>=.325 S2

63 227A -> 245A A -> 245A.28 23A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B.735 Excited State 27: 2.83-A 225A -> 245A A -> 245A A -> 245A A -> 245A.53 23A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A.3 225B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B ev 42.7 nm f=.49 <S**2>=.942 S3

64 235B -> 245B B -> 245B B -> 245B B -> 245B Excited State 28: 2.37-A 225A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B.2 23B -> 245B B -> 245B B -> 245B B -> 245B ev nm f=.4 <S**2>=.54 Excited State 29: 2.7-A 225A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B ev nm f=. <S**2>=.929 S4

65 228B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B.77 Excited State 3: A 225A -> 245A A -> 245A A -> 245A A -> 245A.3 23A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B ev 4.8 nm f=.2 <S**2>=.83 Excited State 3: 2.43-A 225A -> 245A.93 22A -> 245A ev 4.7 nm f=.5 <S**2>=.228 S5

66 229A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B.24 23B -> 245B.59 23B -> 245B -.75 Excited State 32: 2.2-A 225A -> 245A A -> 245A A -> 245A.5 228A -> 245A.32 23A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B.9 228B -> 245B.5 23B -> 245B B -> 245B B -> 245B.5 234B -> 245B B -> 245B ev nm f=.5 <S**2>=.97 Excited State 33: 2.47-A 225A -> 245A A -> 245A A -> 245A A -> 245A ev nm f=. <S**2>=.27 S

67 23A -> 245A A -> 245A A -> 245A A -> 245A.7 234A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B Excited State 34: 2.5-A 22A -> 245A A -> 245A A -> 245A.82 23A -> 245A A -> 245A A -> 245A A -> 245A A -> 248A.53 22B -> 245B B -> 245B B -> 245B B -> 245B.35 23B -> 245B B -> 245B B -> 245B B -> 248B ev nm f=. <S**2>=.97 S7

68 Excited State 35: 2.8-A 224A -> 245A -. 23A -> 245A A -> 248A B -> 245B B -> 245B B -> 248B ev 38. nm f=.8 <S**2>=.724 Excited State 3: 2.5-A 227A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A.3 244A -> 24A A -> 249A A -> 252A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 24B B -> 249B B -> 252B ev nm f=.24 <S**2>=.57 Excited State 37: 2.32-A 227A -> 245A A -> 245A A -> 245A ev nm f=. <S**2>=.45 S8

69 23A -> 245A. 23A -> 245A A -> 245A A -> 245A A -> 249A B -> 245B B -> 245B B -> 245B B -> 245B.23 23B -> 245B B -> 245B B -> 245B B -> 249B.452 Excited State 38: 2.92-A 22A -> 245A A -> 245A A -> 245A A -> 245A B -> 245B B -> 245B B -> 245B B -> 245B ev nm f=.79 <S**2>=.844 Excited State 39: 2.47-A 227A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A.8 242A -> 249A A -> 24A A -> 249A ev 37.8 nm f=.839 <S**2>=.5 S9

70 244A -> 252A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B B -> 249B B -> 24B B -> 249B B -> 252B.397 Excited State 4: A 22A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 245A A -> 255A A -> 248A A -> 248A A -> 25A B -> 245B B -> 245B B -> 245B B -> 245B B -> 245B.37 23B -> 245B B -> 255B B -> 248B B -> 248B B -> 25B ev 37.4 nm f=.354 <S**2>=.3 S7

71 MO245α MO245β MO244α MO244β MO243α MO243β MO242α MO242β Figure S35. The relevant molecular orbitals of 2R calculated at the UMPWPW9/-3+G(d)//UM2X/-3G(d) level. S7

72 . References S. () Sheldrick GM. SHELXS-97 and SHELXL ; University of Gottingen, Germany. (2) Sheldrick GM. SADABS 99; University of Gottingen, Germany. S2. Gaussian 9, Revision D., Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian, Inc., Wallingford CT, 29. S72