General methods. C70 (purchased from SES research Inc.) was purified by Buckyprep column and degassed at room temperature before spectroscopic measurements. See Supplementary Methods for further details.
Synthesis of X70A to X70F. A Schlenk flask was flame-dried under vacuum and filled with argon. To this flask were added dry o-dichlorobenzene (140 mL) and H2O (36 mL) under a stream of argon. After performing three freeze-pump-thaw cycles, [Rh(cod)(MeCN)2]BF4 (45 mg, 0.18 mmol), C70 (500 mg, 0.59 mmol), and 2,7-di-tert- butyl-9,9-dimethylxanthene-4,5-diboronic acid (275 mg, 0.71 mmol) were added to the flask under a stream of argon. After stirring the mixture at 60 °C for 6 h, the mixture was cooled to room temperature. The organic layer was separated and passed through a pad of Celite and silica gel, washing with toluene. The filtrate was concentrated and purified by Buckyprep column (toluene/hexane (v/v) = 1:1 eluent) to afford X70A (140 mg, 20%), X70B (0.8 mg, 0.1%), X70C (12 mg, 1.0%), X70D (13 mg, 1.1%), X70E (0.7 mg, 0.1%) and X70F (3.1 mg, 0.3%) as brown solids. X70A: 1H NMR (500 MHz, CDCl3): δ= 8.03 (d, J = 2.0 Hz, 1H), 7.46 (d, J = 1.5 Hz, 1H), 7.28 (d, J = 1.5 Hz, 1H), 6.76 (d, J = 2.0 Hz, 1H), 5.17 (s, 1H), 3.17 (s, 1H), 1.91 (s, 3H), 1.89 (s, 3H), 1.52 (s, 9H) and 1.20 (s, 9H) ppm; 13C NMR (150 MHz, CDCl3): δ = 159.48, 155.70, 154.92, 152.98, 152.71, 152.68, 152.34, 152.00, 151.15, 151.13, 150.34, 149.93, 149.89, 149.78, 149.65, 149.02, 148.97, 148.70, 148.64, 148.26, 148.17, 147.99, 147.62, 147.31, 147.29, 147.12, 147.09, 147.01, 146.98, 146.86, 146.76, 146.65, 146.41, 146.33, 146.10, 145.98, 145.82, 145.69, 145.64, 145.44, 145.36, 145.29, 145.05, 144.95, 144.92, 144.54, 144.21, 144.17, 144.04, 143.53, 143.36, 143.06, 142.79, 141.99, 141.86, 140.15, 139.90, 139.71, 139.24, 135.71, 135.50, 133.88, 133.79, 132.85, 132.79, 132.59, 132.23, 132.23, 131.46, 131.10, 128.90, 121.29, 120.63, 119.79, 118.94, 68.01, 63.19, 58.15, 50.41, 41.02, 35.63, 35.24, 32.22, 31.89, 29.02 and 22.70 ppm; HR-MS (Spiral MALDI): m/z: calcd for C93H30O, 1162.2291 [M]+; found: 1162.2288; UV-vis (toluene): λmax (ε[103 M–1cm–1]) = 360 (20.3), 401 (22.1), 533 (7.15), 579 (4.93) and 632 (2.92) nm. X70B: 1H NMR (500 MHz, CDCl3): δ= 7.68 (d, J = 2.0 Hz, 2H), 7.29 (d, J = 1.5 Hz, 2H), 5.26 (s, 2H), 1.79 (s, 3H), 1.64 (s, 3H) and 1.28 (s, 18H) ppm; 13C NMR: N.D.; m/z: calcd for C93H30O, 1162.2291 [M]+; found: 1162.2304; UV-vis (toluene): λmax (relative intensity) = 345 (1.00), 375 (0.85), 395 (0.83), 436 (0.94), 472 (0.76), 540 (0.46), 637 (0.12) and 688 (0.10) nm. X70C: 1H NMR (500 MHz, CDCl3): δ= 8.14 (d, J = 1.5 Hz, 1H), 7.50 (d, J = 1.5 Hz, 1H), 7.38 (d, J = 2.0 Hz, 1H), 7.27 (d, J = 2.0 Hz, 1H), 5.61 (d, J = 7.0 Hz, 1H), 5.31 (d, J = 7.0 Hz, 1H), 1.94 (s, 3H), 1.69 (s, 3H), 1.53 (s, 9H) and 1.27 (s, 9H) ppm; 13C NMR: N.D.; HR-MS (Spiral MALDI): m/z: calcd for C93H30O, 1162.2291 [M]+; found: 1162.2292. X70D: 1H NMR (500 MHz, CD2Cl2): d= 8.18 (d, J = 2.5 Hz, 1H), 7.69 (d, J = 2.5 Hz, 1H), 7.39 (d, J = 8.5 Hz, 1H), 7.24 (dd, J = 8.5, 2.5 Hz, 1H), 4.83 (s, 1H), 1.81 (s, 6H), 1.34 (s, 9H), and 1.26 (s, 9H) ppm; 13C NMR: N.D.; HR-MS (Spiral MALDI): m/z: calcd for C93H30O, 1162.2291 [M]+; found: 1162.2308; UV-vis (toluene): λmax (relative intensity) = 341 (1.00), 398 (0.86), 468 (0.61), 536 (0.33) and 662 (0.06) nm. X70E: 1H NMR (500 MHz, CD2Cl2): 8.27 (d, J = 2.0 Hz, 1H), 7.67 (d, J = 2.0 Hz, 1H), 7.29 (d, J = 2.0 Hz, 1H), 7.20 (d, J = 2.0 Hz, 1H), 4.95 (s, 1H), 4.81 (s, 1H), 1.98 (s, 3H), 1.58 (s, 3H), 1.57 (s, 9H), and 1.32 (s, 9H) ppm; 13C NMR: N.D.; HR-MS (Spiral MALDI): m/z: calcd for C93H30O3Na, 1217.2087 [M]+; found: 1217.2073; UV-vis (toluene): λmax (relative intensity) = 358 (1.00), 398 (0.87), 588 (0.18) and 657 (0.07) nm. X70F: 1H NMR (500 MHz, CDCl3): δ = 7.90 (d, J = 2.5 Hz, 1H), 7.65 (d, J = 2.5 Hz, 1H), 7.06 (d, J = 2.5 Hz, 1H), 6.96 (d, J = 2.5 Hz, 1H), 6.44 (s, 1H), 4.86 (s, 1H), 1.83 (s, 6H), 1.49 (s, 9H), and 1.34 (s, 9H) ppm; 13C NMR (150 MHz, CDCl3): δ= 169.03, 168.87, 155.25, 152.36, 152.14, 151.72, 151.33, 151.15, 150.96, 150.77, 150.67, 150.45, 150.14, 150.01, 149.71, 149.68, 149.57, 149.23, 149.13, 149.01, 148.82, 148.65, 148.55, 148.27, 148.09, 148.06, 147.97, 147.73, 147.58, 147.55, 147.51, 147.28, 147.01, 146.68, 146.66, 146.43, 146.41, 146.33, 146.01, 145.88, 145.85, 145.82, 145.65, 145.18, 145.13, 144.73, 144.18, 144.13, 144.06, 144.04, 144.01, 143.88, 143.73, 143.67, 143.64, 143.56, 142.03, 141.33, 139.17, 138.13, 137.79, 134.16, 136.17, 135.84, 135.14, 134.20, 133.99, 133.49, 133.03, 132.53, 132.38, 132.21, 131.76, 131.60, 131.53, 131.44, 131.40, 130.07, 126.36, 124.11, 113.98, 111.51, 81.16, 70.79, 67.25, 59.58, 49.01, 48.98, 35.13, 34.75, 33.39, 33.10, 32.09, 31.79, 31.65, 31.58 and 29.86; HR-MS (Spiral MALDI): m/z: calcd for C93H30O3Na, 1217.2087 [M+Na]+; found: 1217.2089; UV-vis (toluene): λmax (e[103 M–1cm–1]) = 399 (20.0), 455 (15.9) and 623 (2.32) nm.
HPLC purification and CD measurement. Preparative HPLC was performed using a f10 x 250 mm Buckyprep (Nacalai Tesque, Kyoto, Japan) equipped with a JASCO SPD-M10A. Eluent: toluene/hexane = 1/1, v/v. Temperature: at 20 °C. Flow rate: 4.5 mL/min. Injection volume: 5.0 µL. Detection: UV absorption at 326 nm. Chiral resolutions of X70A and X70F were performed at 20 °C using a f10 x 250 mm Cholester (Nacalai Tesque) on recycling preparative HPLC with a photodiode array detector SPD- M10A. Eluent: hexane/i-PrOH = 4/1, v/v. Flow rate: 4.5 mL/min. Injection volume: 5.0 µL. Detection: UV absorption at 326 nm. CD spectra were recorded using a JASCO J- 820 spectropolarimeter.
CPL measurement and analysis. Artefact-free PL and CPL spectra were obtained
using a JASCO CPL-200 spectrofluoropolarimeter, allowing us to avoid second- and third-order stray light due to diffraction grating. The spectrofluoropolarimeter was designed as a prism-based spectrometer with a forward scattering angle of 0° equipped with focusing and collecting lenses, and a movable cuvette holder onto an optical rail enables to adjust the best focal point to maximize PL and CPL signals. A simultaneous CPL and PL measurements allowed to quantitatively evaluate the degree of CPL efficiency relative to PL, known as Kuhn’s dissymmetry factor (glum), that is defined as glum = (IL–IR)/[(IL+IR)/2], where IL and IR refer to the intensity of left- and right-handed CPL, respectively. The glum value was practically evaluated as glum = [ellipticity (in mdeg)/32980/ln10] / PL amplitude (in Volts) at the CPL extremum.
Data availability
The authors declare that the data supporting the findings of this study are available within the paper and its supplementary information file. For full characterization data of new compounds and experimental details, see Supplementary Methods and Figures in Supplementary Information file. The X-ray crystallographic coordinates for structures X70A, X70B and X70F reported in this study have been deposited at the Cambridge Crystallographic Data Centre (CCDC), under deposition numbers 2013940-2013942. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif. All other data are available from the authors upon reasonable request.