Electron Transfer Rate Maxima at Large Donor-Acceptor Distances

Transcription

1 Supporting Information to: Electron Transfer Rate Maxima at Large Donor-Acceptor Distances Martin Kuss-Petermann and Oliver S. Wenger* Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland Table of contents Synthesis and product characterization data Equipment and methods Cyclic voltammetry Energy level scheme for photoinduced charge-separation reactions Spectro-electrochemical data Transient absorption data for compound ref Temperature-dependence studies and activation free energies Absorption of AQ - in 1:1 (v:v) CH3CN / H2O vs. neat CH3CN Determination of electronic coupling matrix elements (HDA) Reactant and product potential energy wells References S2 S12 S13 S15 S16 S19 S20 S23 S24 S25 S27 S1

2 Synthesis and product characterization data The syntheses of compounds 1 4 as well as the syntheses of compounds Ia, IIa, and IIIa have been reported in our recent communication. 1 Syntheses and characterization data for all other new compounds are given below. Scheme S1. Synthesis of the key ligands for compounds Ic, IIc, IIIc (left) and for compounds Ib, IIb, IIIb (right). (a) Pd(PPh3)4, Na2CO3, THF/H2O; (b) Pd(dba)2, [HP t Bu3]BF4, t BuOK, toluene; (c) bis(pinacol)diboron, Pd(dba)2, PCy3, KOAc, 1,4-dioxane; (d) ICl, CH2Cl2; (e) bis(pinacol)diboron, PdCl2(PPh3)2, KOAc, DMSO. Compound 5. Compound 1 (1.10 g, 2.50 mmol) and 5,5 -dibromo-2,2 -bipyridine (2) 2 (1.18 g, 3.75 mmol), were dissolved in a mixture of THF (40 ml) and water (10 ml) along with Na2CO3 (795 mg, 7.50 mmol) and Pd(PPh3)4 (144 mg, mmol). The mixture was deaerated and reacted at reflux under N2 overnight. After cooling to room temperature, the product was extracted with CH2Cl2. The combined organic phases were dried over Na2SO4 prior to evaporating the solvents. Recrystallization from toluene (150 ml) was followed by washing with diethyl ether. Compound 5 was obtained as a yellow solid (1.16 g, 2.12 mmol, 85%) after drying under vacuum. 1 H NMR (400 MHz, CD2Cl2): [ppm] 8.75 (dd, J = 2.4, 0.7 Hz, 1 H), 8.70 (dd, J = 2.3, 0.9 Hz, 1 H), 8.49 (dd, J = 8.1, 0.9 Hz, 1 H), 8.41 (d, J = 8.4 Hz, 1 H), 8.38 (d, J = 8.0 Hz, 1 H), (m, 3 H), 7.99 (dd, J = 8.5, 2.4 Hz, 1 H), (m, 4 H), 7.29 (s, 1 H), 7.27 (s, 1 H), 2.36 (s, 3 H), 2.35 (s, 3 H). S2

3 Compound 6 was prepared in analogous manner as compound 5, using compound 1 (1.10 g, 2.50 mmol) and compound 3 (1.57 g, 3.00 mmol) 1 as starting materials. Identical Na2CO3 and Pd(PPh3)4 quantities as reported above for compound 5 were used, the solvent volumes were also identical. Compound 6 was obtained as a pale yellow solid (1.06 g, 1.41 mmol, 56%). 1 H NMR (400 MHz, CD2Cl2): [ppm] 8.67 (dd, J = 6.8, 2.3 Hz, 1 H), 8.57 (d, J = 2.3 Hz, 1 H), 8.50 (d, J = 8.2 Hz, 1 H), 8.47 (d, J = 8.0 Hz, 1 H), (m, 4 H), (m, 5 H), 7.45 (s, 1 H), (m, 2 H), 7.12 (s, 1 H), 7.05 (s, 1 H), 7.04 (s, 1 H), 2.35 (s, 3 H), (m, 3 H), 2.26 (s, 3 H), 2.21 (s, 3 H), 2.09 (s, 3 H), 2.08 (s, 3 H). MS (ESI TOF) m/z: [M]+H + Calcd for C48H37N2O2Br+H , 755.2; Found 753.0, Compound 7 was prepared from compound 1 (701 mg, 1.60 mmol) 1 and compound 4 (1.40 g, 1.92 mmol) 1 in analogous manner as compound 5. Na2CO3 (509 mg, 4.80 mmol) and Pd(PPh3)4 (92 mg, 0.08 mmol) were used in THF (40 ml) and water (10 ml). After reaction, the mixture was filtered and the solid residue was washed with water and diethyl ether to afford the product as a beige solid (1.19 g, 1.24 mmol, 78%). 1 H NMR (400 MHz, CD2Cl2): [ppm] (m, 2 H), 8.57 (d, J = 8.0 Hz, 2 H), (m, 4 H), (m, 5 H), 7.48 (s, 1 H), 7.27 (s, 2 H), 7.23 (s, 1 H), 7.17 (s, 1 H), 7.15 (s, 1 H), 7.08 (s, 2 H), 7.04 (s, 1 H), 7.03 (s, 1 H), 2.40 (s, 1 H), 2.37 (s, 3 H), 2.34 (s, 6 H), 2.18 (s, 3 H), 2.17 (s, 3 H), 2.14 (s, 6 H), 2.08 (s, 6 H). MS (ESI TOF) m/z: [M]+H + Calcd for C64H53N2O2Br+H , 963.3; Found 961.0, Compound 10. Commercial 1-bromo-3,4-dimethoxybenzene (8) (4.77 g, 22.0 mmol), commercial 4-chloro-2,5- dimethylaniline (9) (1.56 g, 10.0 mmol), Pd(dba)2 (288 mg, 0.5 mmol), HP t Bu3BF4 (145 mg, 0.5 mmol) and t BuOK (3.37 g, 30.0 mmol) were suspended in dry toluene (10 ml). The reaction mixture was deaerated and then heated to 90 C under N2 overnight. Water (150 ml) was added, and the product was extracted with CH2Cl2. The combined organic phases were dried over Na2SO4 prior to evaporating the solvents. Chromatography on silica gel column with a 1:1 (v:v) mixture of pentane and diethyl ether afforded the product as a beige solid (2.84 g, 6.64 mmol, 66%). 1 H NMR (400 MHz, acetone-d6): [ppm] 7.24 (s, 1 H), 6.99 (s, 1 H), 6.82 (d, J = 8.6 Hz, 2 H), 6.61 (d, J = 2.5 Hz, 2 H), 6.34 (dd, J = 8.6, 2.5 Hz, 2 H), 3.76 (s, 6 H), 3.65 (s, 6 H), 2.24 (s, 3 H), 1.98 (s, 3 H). Compound 11. A mixture of compound 10 (856 mg, 2.0 mmol), bis(pinacol)diboron (609 mg, 2.4 mmol), KOAc (393 mg, 4.0 mmol), PCy3 (67 mg, 0.24 mmol) and Pd(dba)2 (58 mg, 0.1 mmol) in 1,4-dioxane (15 ml) was deaerated and reacted at 80 C under N2 for 24 hours. After cooling to room temperature, the mixture was treated with water (60 ml) and saturated NH4Cl solution (20 ml). The aqueous phase was extracted with CH2Cl2, and the combined organic phases were dried over anhydrous Na2SO4 prior to evaporating the solvent. Chromatography on silica gel column with a 1:1 (v:v) mixture of pentane and diethyl ether afforded a white solid (1.00 g). 1 H NMR spectroscopy revealed that the obtained product consisted of a 3:1 mixture of the desired product (11) (800 mg, 1.5 mmol, 75%) and starting material (9) in which the chloro-substituent had been replaced by a hydrogen atom. 1 H NMR of compound 11 (400 MHz, acetone-d6): [ppm] 7.56 (s, 1 H), (m, 3 H), 6.61 (d, J = 2.6 Hz, 2 H), 6.35 (dd, J = 8.6, 2.6 Hz, 2 H), 3.76 (s, 6 H), 3.65 (s, 6H), 2.38 (s, 3 H), 1.95 (s, 3 H), 1.34 (s, 12 H). S3

4 Compound Methylaniline (12) (1.07 g, 10.0 mmol), 4-bromo-toluene (13) (1.88 g, 11.0 mmol), Pd(dba)2 (288 mg, 0.5 mmol), HP t Bu3BF4 (145 mg, 0.5 mmol), and t BuOK (3.37 g, 30.0 mmol) were suspended in dry toluene (30 ml). After deaerating, the mixture was reacted at 90 C under N2 overnight. After cooling to room temperature, water (100 ml) was added and the mixture was acidified with aqueous HCl prior to extracting with CH2Cl2. The combined organic phases were dried over anhydrous Na2SO4, and then the solvents were evaporated. Chromatography on silica gel column using a 5:1 (v:v) mixture of pentane and diethyl ether as the eluent afforded the product as a beige solid (1.64 g, 8.33 mmol, 83%). 1 H NMR (400 MHz, CD2Cl2): [ppm] (m, 4 H), (m, 4 H), 5.60 (s, 1 H), 2.27 (s, 6 H). Compound 16. Compound 14 (1.64 g, 8.33 mmol), 2-bromo-5-trimethylsilyl-p-xylene (15) (2.36 g, 9.2 mmol), 3 Pd(dba)2 (239 mg, 0.4 mmol), HP t Bu3BF4 (121 mg, 0.4 mmol) and t BuOK (2.80 g, 25.0 mmol) were suspended in dry toluene (30 ml). After deaerating, the mixture was reacted at 90 C under N2 overnight. Water (100 ml) was added to the cooled reaction mixture, and the product was extracted with CH2Cl2. The combined organic phases were dried over anhydrous Na2SO4 prior to solvent evaporation. Chromatography with 10:1 (v:v) pentane and diethyl ether on silica gel column afforded the product as a white solid (2.34 g, 6.28 mmol, 75%). 1 H NMR (400 MHz, acetone-d6): [ppm] 7.32 (s, 1 H), (m, 4 H), 6.84 (s, 1 H), (m, 4 H), 2.34 (s, 3 H), 2.25 (s, 6 H), 1.95 (s, 3 H), 0.32 (s, 9 H). Compound 17. Compound 16 (2.34 g, 6.28 mmol) was dissolved in dry CH2Cl2 (30 ml) and cooled to -78 C prior to adding a solution of ICl (2.04 g, 12.6 mmol) in dry CH2Cl2 (10 ml). The resulting mixture was stirred at -78 C for 10 minutes and then an aqueous solution of Na2S2O3 was added. After phase separation, the aqueous phase was extracted with CH2Cl2 and the combined organic phases were dried over Na2SO4 before evaporating the solvents. Chromatography on silica gel column with a 5:1 (v:v) mixture of pentane and diethyl ether afforded the product as a white solid (2.54 g, 5.9 mmol, 95%). 1 H NMR (400 MHz, acetone-d6): [ppm] 7.72 (s, 1 H), (m, 4 H), 6.99 (s, 1 H), (m, 4 H), 2.30 (s, 3 H), 2.25 (s, 6 H), 1.93 (s, 3 H). Compound 18. Compound 17 (2.56 g, 6.0 mmol), bis(pinacol)diboron (2.28 g, 9.0 mmol), KOAc (2.36 g, 24.0 mmol), and Pd(PPh3)2Cl2 (211 mg, 0.3 mmol) in DMSO (30 ml) were deaerated and reacted at 90 C under N2 overnight. After cooling to room temperature, the reaction mixture was treated with water (100 ml) and saturated aqueous NH4Cl solution (20 ml). The aqueous phase was extracted with CH2Cl2, and the combined organic phases were dried over anhydrous Na2SO4 prior to evaporating the solvents. A 10:1 (v:v) mixture of pentane and diethyl ether was used for chromatography on silica gel column, and this yielded the product as a white solid (1.84 g, 4.3 mmol, 72%). 1 H NMR (400 MHz, acetone-d6): [ppm] 7.59 (s, 1 H), (m, 4 H), 6.83 (s, 1 H), (m, 4 H), 2.39 (s, 3 H), 2.26 (s, 6 H), 1.93 (s, 3 H), 1.35 (s, 12 H). Ligand 19. Compound 5 (382 mg, 0.7 mmol), boronic ester 11 (crude: 559 mg, containing 436 mg, 0.84 mmol of pure 11, see above), Na2CO3 (223 mg, 2.1 mmol), and Pd(PPh3)4 (41 mg, mmol) in THF (15 ml) and H2O (4 ml) were deaerated and then heated to reflux under N2 overnight. After cooling to room temperature, the product was extracted S4

5 with CH2Cl2. The combined organic phases were dried over anhydrous Na2SO4 prior to solvent evaporation. Chromatography occurred on silica gel column. At first, the eluent was a 1:1 (v:v) mixture of pentane and diethyl ether, then pure diethyl ether, and finally diethyl ether with 2% methanol was employed. This afforded the product as a yellow-brownish solid (515 mg, 0.6 mmol, 86%). 1 H NMR (400 MHz, CD2Cl2): [ppm] 8.72 (ddd, J = 7.4, 2.3, 0.8 Hz, 2 H), 8.55 (td, J = 8.0, 0.9 Hz, 2 H), 8.38 (d, J = 8.0 Hz, 1 H), (m, 3 H), (m, 5 H), 7.30 (s, 2 H), 7.17 (s, 1 H), 7.01 (s, 1 H), 6.76 (d, J = 8.7 Hz, 2 H), 6.64 (d, J = 2.6 Hz, 2 H), 6.44 (dd, J = 8.6, 2.5 Hz, 2 H), 3.80 (s, 6 H), 3.71 (s, 6 H), 2.38 (s, 3 H), 2.36 (s, 3 H), 2.25 (s, 3 H), 2.05 (s, 3 H). MS (ESI TOF) m/z: [M]+H + Calcd for C56H47N3O6+H ; Found 858. Ligand 20. Compound 6 (337 mg, 0.5 mmol), boronic ester 11 (crude: 416 mg, containing 312 mg, 0.6 mmol of pure 11, see above), Na2CO3 (159 mg, 1.5 mmol), and Pd(PPh3)4 (29 mg, mmol) in THF (15 ml) and H2O (4 ml) were deaerated and then heated to reflux under N2 for two days. After cooling to room temperature, the product was extracted with CH2Cl2 and the combined organic phases were dried over Na2SO4 before evaporating the solvents. Chromatography on silica gel column started with a 1:1 (v:v) mixture of pentane and diethyl ether. Then pure diethyl ether was used, and finally the eluent was diethyl ether with 2% methanol. This yielded the product as a yellowbrownish solid (515 mg, 0.6 mmol, 86%). 1 H NMR (400 MHz, CD2Cl2): [ppm] 8.75 (ddd, J = 4.1, 2.3, 0.9 Hz, 2 H), 8.57 (ddd, J = 8.1, 1.5, 0.8 Hz, 2 H), 8.38 (d, J = 8.0 Hz, 1 H), (m, 3 H), (m, 5 H), 7.24 (s, 2 H), 7.14 (s, 1 H), 7.13 (s, 3 H), 6.99 (s, 2 H), 6.76 (d, J = 8.6 Hz, 2 H), 6.63 (d, J = 2.6 Hz, 2 H), 6.46 (dd, J = 8.6, 2.6 Hz, 2 H), 3.80 (s, 6 H), 3.70 (s, 6 H), 2.37 (s, 3 H), 2.36 (s, 3 H), 2.34 (s, 3 H), 2.17 (s, 6 H), 2.13 (s, 3 H), 2.04 (s, 3 H), 2.03 (s, 3 H). MS (ESI TOF) m/z: [M]+H + Calcd for C72H63N3O6+H ; Found Ligand 21. Compound 7 (481 mg, 0.5 mmol), boronic ester 11 (crude: 416 mg, containing 312 mg, 0.6 mmol of pure 11, see above), Cs2CO3 (489 mg, 1.50 mmol), and Pd(PPh3)4 (29 mg, mmol) in DMF (50 ml) were deaerated prior to reacting the mixture at 100 C under N2 for 3 days. After cooling to room temperature, water (200 ml) was added. The precipitate was filtered, washed with water and was then dried. The crude product was purified on silica gel column using CH2Cl2 with 1.5% methanol and 1.5% triethylamine as the eluent. A second column chromatography on silica gel was performed with diethyl ether containing 2% triethylamine, yielding the pure product as a beige solid (137 mg, 0.11 mmol, 21%). 1 H NMR (400 MHz, CD2Cl2): [ppm] (m, 2 H), 8.58 (d, J = 8.2 Hz, 2 H), 8.38 (d, J = 8.0 Hz, 1 H), (m, 3 H), (m, 5 H), 7.27 (s, 2 H), 7.26 (s, 1 H), (m, 3 H), 7.08 (s, 3 H), (m, 2 H), 6.99 (s, 1 H), 6.76 (d, J = 8.6 Hz, 2 H), 6.64 (d, J = 2.6 Hz, 2 H), 6.46 (dd, J = 8.6, 2.6 Hz, 2 H), 3.80 (s, 6 H), 3.70 (s, 6 H), 2.38 (s, 3H), 2.37 (s, 3 H), 2.35 (s, 3 H), (m, 18 H), 2.10 (s, 3 H), (m, 6 H). MS (ESI TOF) m/z: [M]+H + Calcd for C88H79N3O6+H ; Found Ligand 22. Compound 5 (382 mg, 0.7 mmol), compound 18 (359 mg, 0.84 mmol), Na2CO3 (223 mg, 2.1 mmol), and Pd(PPh3)4 (41 mg, mmol) in THF (15 ml) and water (5 ml) was dearated and then heated to reflux under N2 overnight. After cooling to room temperature, the mixture was extracted with CH2Cl2. The combined organic phases were dried over anhydrous Na2SO4, and the solvents were evaporated. Column chromatography on silica gel started with a 2:1 (v:v) mixture of pentane and CH2Cl2. Later the eluent was change to pure CH2Cl2, and finally to CH2Cl2 S5

6 containing 2% triethylamine. This afforded the product as an orange solid (389 mg, 0.51 mmol, 73%). 1 H NMR (400 MHz, CD2Cl2): [ppm] 8.72 (dd, J = 8.3, 2.3 Hz, 2 H), 8.55 (t, J = 8.0 Hz, 2 H), 8.38 (d, J = 8.0 Hz, 1 H), (m, 3 H), (m, 5 H), 7.30 (s, 2 H), 7.19 (s, 1 H), (m, 5 H), (m, 4 H), 2.38 (s, 3 H), 2.36 (s, 3 H), 2.29 (s, 6 H), 2.25 (s, 3 H), 2.03 (s, 3 H). Ligand 23. Compound 6 (339 mg, 0.45 mmol), boronic ester 18 (231 mg, 0.54 mmol), Na2CO3 (143 mg, 1.35 mmol), and Pd(PPh3)4 (26 mg, mmol) in THF (12 ml) and H2O (3 ml) were dearated prior to heating at reflux under N2 for 2 days. After cooling to room temperature, the reaction mixture was extracted with CH2Cl2. The combined organic phases were dried over Na2SO4 prior to evaporating the solvents. Chromatography on silica gel column using CH2Cl2 with 2% methanol as the eluent afforded the pure product as an orange solid (329 mg, 0.34 mmol, 75%). 1 H NMR (400 MHz, CD2Cl2): [ppm] (m, 2 H), (m, 2 H), 8.38 (d, J = 8.0 Hz, 1 H), (m, 3 H), (m, 5 H), 7.27 (s, 2 H), 7.24 (s, 1 H), 7.13 (s, 3 H), (m, 4 H), 7.01 (s, 2 H), (m, 4 H), 2.36 (s, 3 H), 2.34 (s, 3 H), 2.29 (s, 6 H), 2.17 (s, 6 H), 2.15 (s, 3 H), 2.03 (s, 3 H), 2.01 (s, 3 H). The key ligand for compound IIIc could not be synthesized using the strategy outline in Scheme S1. A completely different synthetic strategy had to be followed for ligand 34, as illustrated in Scheme S2. Scheme S2. Synthesis of ligand 34 for compound IIIb. (a) n-buli, CuCN, duroquinone, THF; (b) n-buli, TMSCl; THF, -78 C (c) Pd(PPh3)4, Na2CO3, THF/H2O; (d) ICl, CH2Cl2; (e) bis(pinacol)diboron, PdCl2(PPh3)2, KOAc, DMSO. Compound 25. To a solution of commercial 1,4-dibromo-p-xylene (24) (5.28 g, 20.0 mmol) in dry THF (150 ml) at - 78 C was added n-butyllithium in hexane (2.5 M, 8.8 ml, 22.0 mmol) dropwise over a period of approximately 20 minutes. The mixture was reacted at -78 C for 1.5 hours prior to addition of CuCN (896 mg, 10.0 mmol). The reaction mixture was allowed to warm up until all CuCN dissolved. Duroquinone (4.93 g, 30.0 mmol) was added, and this caused an instant color change to deep blue. After stirring for 3 hours at room temperature, aqueous 2 M HCl was added and the product was extracted with diethyl ether. The combined organic phases were dried over anhydrous Na2SO4 before evaporating the solvents. Purification of the raw product on silica gel column with pentane eluent S6

7 afforded the product as a viscous colorless oil (3.35 g, 9.1 mmol, 91%). 1 H NMR (400 MHz, CDCl3): [ppm] 7.43 (s, 2 H), 6.92 (s, 2 H), 2.36 (s, 6 H), 1.98 (s, 6 H). Compound 26. To a solution of compound 25 (3.35 g, 9.1 mmol) in dry THF (100 ml) at -78 C was added n- butyllithium in hexane (2.5 M, 3.83 ml, 9.6 mmol) in dropwise fashion over approximately 15 minutes. This mixture was reacted at -78 C under N2 for 1 hour prior to adding trimethylsilyl chloride (1.27 ml, 10.0 mmol). Then the mixture was allowed to warm up to room temperature. Water (100 ml) was added, and the product was extracted with diethyl ether. The combined organic phases were dried over anhydrous Na2SO4 before solvent evaporation. Chromatography on silica gel column with pentane gave the product as a viscous colorless oil (2.56 g, 7.1 mmol, 78%). 1 H NMR (400 MHz, CDCl3): [ppm] 7.43 (s, 1 H), 7.31 (s, 1 H), 6.97 (s, 1 H), 6.85 (s, 1 H), 2.42 (s, 3 H), 2.36 (s, 3 H), 2.02 (s, 3 H), 2.01 (s, 3 H), 0.35 (s, 9 H). Compound 27. Compound 26 (904 mg, 2.5 mmol), boronic ester 18 (1.28 g, 3.0 mmol), Na2CO3 (795 mg, 7.5 mmol), and Pd(PPh3)4 (144 mg, 0.13 mmol) in THF (20 ml) and H2O (5 ml) were deaerated prior to heating at reflux under N2 overnight. The product was extracted with CH2Cl2 after cooling the reaction mixture to room temperature. The combined organic phases were dried over anhydrous Na2SO4 prior to evaporating the solvents. Chromatography on silica gel column using a 5:1 (v:v) mixture of pentane and CH2Cl2 as the eluent afforded the pure product as a white solid (1.06 g, 1.8 mmol, 73%). 1 H NMR (400 MHz, CD2Cl2): [ppm] 7.35 (s, 1 H), (m, 6 H), (m, 3 H), (m, 4 H), 2.44 (s, 3 H), 2.28 (s, 6 H), (m, 9 H), 2.00 (s, 6 H), 0.36 (s, 9 H). Compound 28. Compound 27 (1.06, 1.8 mmol) was dissolved in dry CH2Cl2 (30 ml) and cooled to 0 C before addition a solution of ICl (591 mg, 3.6 mmol) in dry CH2Cl2 (10 ml). The resulting mixture was stirred at 0 C for 30 minutes and then aqueous Na2S2O3 solution was added. After phase separation the organic layer was extracted with CH2Cl2. The combined organic phases were dried over anhydrous Na2SO4 prior to solvent evaporation. Column chromatography on silica gel with 5:1 (v:v) pentane / CH2Cl2 afforded the product as a white solid (1.08 g, 1.7 mmol, 93%). 1 H NMR (400 MHz, CD2Cl2): [ppm] 7.75 (s, 1 H), (m, 6 H), (m, 3 H), (m, 4 H), 2.42 (s, 3 H), 2.28 (s, 6 H), (m, 15 H). Compound 29. Compound 28 (1.08 g, 1.7 mmol), bis(pinacol)diboron (648 mg, 2.6 mmol), KOAc (667 mg, 6.8 mmol), and Pd(PPh3)2Cl2 (60 mg, mmol) in DMSO (25 ml) was deaerated and reacted at 90 C under N2 overnight. The reaction mixture was allowed to cool to room temperature before treating it with water (100 ml) and saturated aqueous NH4Cl (20 ml). The aqueous layer was extracted with CH2Cl2, and the combined organic phases were dried over anhydrous Na2SO4 prior to evaporating the solvents. Column chromatography on silica gel with a 5:1 (v:v) mixture of pentane and CH2Cl2 as the eluent afforded the product as a white solid (710 mg, 1.1 mmol, 66%). 1 H NMR (400 MHz, CD2Cl2): [ppm] = 7.64 (s, 1 H), (m, 6 H), (m, 3 H), (m, 4 H), 2.51 (s, 3 H), 2.28 (s, 6 H), (m, 6 H), 2.02 (s, 3 H), (m, 6 H), 1.36 (s, 12 H). S7

8 Compound 30. 5,5 -Dibromo-2,2 -bipyridine (2) (527 mg, 1.7 mmol), 2 compound 29 (710 mg, 1.1 mmol), Na2CO3 (356 mg, 3.4 mmol), and Pd(PPh3)4 (65 mg, mmol) were dissolved in a biphasic mixture of THF (15 ml) and H2O (5 ml). After deaerating, the mixture was reacted at reflux under N2 overnight. The reaction mixture was allowed to cool to room temperature before extracting with CH2Cl2. The combined organic phases were dried over anhydrous Na2SO4 prior to evaporating the solvents. The crude product was purified by column chromatography on C18 reversed phase silica gel using at first acetonitrile, then acetone, and finally CH2Cl2 as an eluent. This afforded the pure product as a white solid (372 mg, 0.5 mmol, 45%). 1 H NMR (400 MHz, CD2Cl2): [ppm] 8.75 (dd, J = 2.4, 0.7 Hz, 1 H), 8.71 (dd, J = 2.3, 0.9 Hz, 1 H), 8.48 (dd, J = 8.2, 0.9 Hz, 1 H), 8.42 (dd, J = 8.5, 0.8 Hz, 1 H), 7.99 (dd, J = 8.5, 2.4 Hz, 1 H), 7.88 (dd, J = 8.3, 2.3 Hz, 1 H), 7.22 (s, 1 H), 7.13 (d, J = 4.2 Hz, 1 H), (m, 7 H), 6.99 (s, 1 H), (m, 4 H), 2.33 (s, 3 H), 2.29 (s, 6 H), (m, 9 H), (m, 6 H). Compound 31. Compound 1 (789 mg, 1.8 mmol), compound 26 (542 mg, 1.5 mmol), Na2CO3 (477 mg, 4.5 mmol), and Pd(PPh3)4 (87 mg, mmol) in THF (20 ml) and H2O (5 ml) were deaerated and then heated to reflux under N2 overnight. After cooling to room temperature, the product was extracted with CH2Cl2. The combined organic phases were dried over Na2SO4 before evaporating. Chromatography on silica gel column occurred using a 1:1 (v:v) mixture of pentane and CH2Cl2 as the eluent, yielding the pure product as a yellow solid (803 mg, 1.4 mmol, 91%). 1 H NMR (400 MHz, CDCl3): [ppm] 8.39 (d, J = 8.0 Hz, 1 H), (m, 3 H), 7.86 (dd, J = 8.0, 1.8 Hz, 1 H), (m, 2 H), 7.35 (s, 1 H), 7.22 (s, 1 H), 7.15 (s, 1 H), (m, 2 H), 6.99 (s, 1 H), 2.46 (s, 3 H), 2.33 (s, 3 H), (m, 3 H), (m, 9 H), 0.37 (s, 9 H). Compound 32. To a solution of compound 31 (813 mg, 1.4 mmol) in dry CH2Cl2 (40 ml) was added a solution of ICl (334 mg, 2.1 mmol) in dry CH2Cl2 (10 ml). The reaction mixture was stirred for 1 hours at room temperature, and then saturated aqueous Na2S2O3 solution was added. Aqueous and organic layers were separated, and the former was extracted with CH2Cl2. The combined organic phases were dried over anhydrous Na2SO4 prior to evaporating the solvents. Chromatography on short silica gel column with CH2Cl2 gave the product as a pale yellow solid (758 mg, 1.2 mmol, 85%). 1 H NMR (400 MHz, CDCl3): d [ppm] 8.39 (d, J = 8.0 Hz, 1 H), (m, 3 H), (m, 3 H), 7.75 (s, 1 H), 7.22 (s, 1 H), 7.13 (d, J = 3.3 Hz, 1 H), 7.06 (d, J = 3.0 Hz, 1 H), 7.04 (d, J = 5.4 Hz, 1 H), 6.98 (d, J = 5.3 Hz, 1 H), 2.43 (s, 3 H), 2.33 (s, 3 H), (m, 3 H), 2.10 (s, 3 H), (m, 6 H). Compound 33. Compound 32 (758 mg, 1.2 mmol), bis(pinacol)diboron (446 mg, 1.8 mmol), KOAc (459 mg, 4.7 mmol), and Pd(PPh3)4 (41 mg, 0.06 mmol) in DMSO were deaerated and then reacted at 90 C under N2 overnight. After cooling to room temperature, the mixture was treated with water (80 ml) and saturated aqueous NH4Cl (20 ml). After phase separation, the aqueous layer was extracted with CH2Cl2. The combined organic phases were dried over anhydrous Na2SO4 prior to evaporation. Chromatography on silica gel column started with a 1:1 (v:v) mixture of pentane and CH2Cl2 as the eluent, and then pure CH2Cl2 was used. This afforded the product as a yellow solid (536 mg, 0.83 mmol, 71%). 1 H NMR (400 MHz, CD2Cl2): [ppm] 8.39 (d, J = 8.0 Hz, 1 H), (m, 3 H), 7.86 (dd, J = 8.0, 1.9 Hz, 1 H), (m, 2 H), 7.69 (s, 1 H), 7.22 (s, 1 H), 7.15 (s, 1 H), (m, 3 H), 2.55 (s, 3 H), 2.33 (s, 3 H), (m, 3 H), (m, 6 H), 2.05 (s, 3 H). S8

9 Ligand 34. Compound 30 (372 mg, 0.5 mmol), compound 32 (388 mg, 0.6 mmol), Na2CO3 (159 mg, 1.5 mmol), and Pd(PPh3)4 (29 mg, mmol) were dissolved in THF (16 ml) and water (4 ml). The reaction mixture was deaerated prior to heating to reflux under N2 overnight. After cooling to room temperature, the product was extracted with CH2Cl2 and the combined organic phases were dried over anhydrous Na2SO4. Chromatography on silica gel column started with a 5:1 (v:v) mixture of pentane and diethyl ether containing 1% methanol and 1% triethylamine. Later, 1:1 (v:v) pentane and CH2Cl2 with 2% methanol was used as an eluent. The crude product was dissolved in a minimal amount of CH2Cl2 and then added to methanol. The precipitate was dried under vacuum, yielding the pure product a pale pink solid (438 mg, 0.04 mmol, 74%). 1 H NMR (400 MHz, CD2Cl2): [ppm] 8.76 (s, 2 H), 8.58 (d, J = 8.1 Hz, 2 H), 8.38 (d, J = 8.0 Hz, 1 H), (m, 3 H), (m, 5 H), (m, 3 H), (m, 3 H), (m, 9 H), 7.00 (s, 1 H), (m, 4 H), 2.38 (s, 3 H), 2.37 (s, 3 H), 2.35 (s, 3 H), 2.29 (s, 6 H), (m, 21 H), (m, 6 H). MS (ESI TOF) m/z: [M]+H + Calcd for C86H75N3O2+H ; Found Compound Ib. Ligand 22 (192 mg, 0.25 mmol) and Ru(bpy)2Cl2 (121 mg, 0.25 mmol) in ethanol (12 ml) and chloroform (4 ml) were heated to reflux under N2 overnight. Then the solvents were evaporated, and the solid residue was subjected to chromatography on silica gel column. At first, the eluent was pure acetone, then 9:1 (v:v) acetone and H2O, and finally 9:1 (v:v) acetone and H2O with 1% saturated aqueous KNO3 was used. KPF6 was added to the desired chromatography fractions, and the acetone was evaporated. The product was then extracted with CH2Cl2, the combined CH2Cl2 phases were washed with water, and then evaporated. This afforded the product as a red solid (149 mg, 0.1 mmol, 41%). 1 H NMR (400 MHz, acetone-d6): [ppm] 8.98 (dd, J = 10.1, 8.4 Hz, 2 H), (m, 4 H), 8.36 (d, J = 8.0 Hz, 1 H), (m, 5 H), (m, 5 H), (m, 3 H), 8.07 (s, 2 H), (m, 2 H), 7.92 (dd, J = 8.0, 1.8 Hz, 1 H), (m, 2 H), (m, 2 H), 7.27 (s, 1 H), 7.23 (s, 1 H), 7.14 (s, 1 H), (m, 4 H), 6.91 (s, 1 H), (m, 4 H), 2.29 (s, 3 H), 2.27 (s, 6 H), 2.10 (s, 3 H), 1.95 (s, 6 H). HRMS (ESI TOF) m/z: [M] 2+ Calcd for C74H59N7O2Ru ; Found Anal. Calcd for C74H59N7O2F12P2Ru 2CH3(CO)CH3 (%): C, 58.29; H, 4.77; N, Found: C, 58.24; H, 4.98; N, Compound IIb. Ligand 23 (195 mg, 0.2 mmol) and Ru(bpy)2Cl2 (97 mg, 0.2 mmol) in ethanol (12 ml) and chloroform (4 ml) were reacted at reflux under N2 overnight. After evaporating the solvents, the solid residue was purified by column chromatograpy on a silica gel stationary phase. The initial eluent was pure acetone, then 9:1 (v:v) acetone and water, and finally 9:1 (v:v) acetone and water with 1% saturated aqueous KNO3 was employed. To the desired chromatography fractions KPF6 was added, and the acetone was evaporated. The product was extracted with CH2Cl2, the combined organic phases were washed with water, and then evaporated to dryness. This afforded the pure product as a red solid (111 mg, mmol, 33%). 1 H NMR (400 MHz, acetone-d6): [ppm] 9.01 (dd, J = 8.5, 2.5 Hz, 2 H), (m, 4 H), 8.38 (d, J = 8.0 Hz, 1 H), (m, 6 H), (m, 5 H), (m, 2 H), (m, 2 H), (m, 3 H), (m, 2 H), (m, 2 H), 7.32 (s, 1 H), (m, 2 H), (m, 7 H), 7.00 (s, 1 H), 6.93 (s, 1 H), (m, 4 H), 2.34 (s, 3 H), 2.27 (s, 6 H), 2.09 (s, 9 H), (m, 6 H), 2.00 (s, 3 H), 1.95 (s, 3 H). HRMS (ESI TOF) m/z: [M] 2+ Calcd for C90H75N7O2Ru ; Found Anal. Calcd for C90H75N7O2F12P2Ru 2CH3(CO)CH3 2H2O (%): C, 63.05; H, 4.84; N, Found: C, 63.20; H, 5.09; N, S9

10 Compound IIIb. Ligand 34 (438 mg, 0.37 mmol) and Ru(bpy)2Cl2 (179 mg, 0.37 mmol) in ethanol (21 ml) and chloroform (7 ml) were reacted at reflux under N2 for 2 days. Then the solvents were evaporated. The solid residue was subjected to column chromatography with a silica gel stationary phase. At first, the eluent was pure acetone, then 9:1 (v:v) acetone and water, and finally a 9:1 (v:v) mixture of acetone and water with 1% saturated aqueous KNO3 solution was used. KPF6 was added to the desired chromatography fractions, and the acetone was evaporated. The product was then extracted with CH2Cl2, and the combined organic phases were washed with water prior to evaporating the solvents. After drying under vacuum, the pure product was obtained as a red solid (157 mg, mmol, 22%). 1 H NMR (400 MHz, acetone-d6): [ppm] 9.02 (d, J = 8.5 Hz, 2 H), 8.90 (d, J = 8.2 Hz, 4 H), 8.40 (d, J = 8.0 Hz, 1 H), (m, 6 H), (m, 5 H), (m, 2 H), (m, 2 H), (m, 3 H), (m, 2 H), (m, 2 H), 7.34 (s, 1 H), (m, 2 H), 7.15 (s, 1 H), 7.11 (s, 1 H) (m, 7 H), 7.03 (s, 1 H), 7.02 (s, 1 H), 7.00 (s, 1 H), 6.97 (s, 1 H), (m, 4 H), 2.37 (s, 3 H), 2.28 (s, 6 H), 2.16 (d, J = 3.5 Hz, 3 H), 2.12 (s, 3 H), (m, 21 H), 2.03 (s, 3 H), 2.01 (s, 3 H). HRMS (ESI TOF) m/z: [M] 2+ Calcd for C106H91N7O2Ru ; Found Anal. Calcd for C106H91N7O2F12P2Ru 1.5CH3(CO)CH3 (%): C, 67.27; H, 5.11; N, Found: C, 67.08; H, 5.39; N, Compound Ic. A solution of ligand 19 (257 mg, 0.3 mmol) and Ru(bpy)2Cl2 (145 mg, 0.3 mmol) in ethanol (18 ml) and chloroform (6 ml) was heated to reflux under N2 overnight. Then the solvents were evaporated and the solid residue was purified by chromatography on silica gel column using at first acetone as an eluent. Then a 9:1 (v:v) mixture of acetone and water with 1% saturated aqueous KNO3 was used as an eluent. KPF6 was added to the desired chromatography fractions and acetone was completely evaporated. The remaining aqueous phases were extracted with CH2Cl2. After drying over anhydrous Na2SO4 and solvent evaporation, the product was obtained as a red solid (281 mg, 0.18 mmol, 60%). 1 H NMR (400 MHz, acetone-d6): [ppm] (m, 2 H), (m, 4 H), (m, 14 H), 8.07 (dd, J = 2.0, 0.7 Hz, 1 H), (m, 3 H), 7.92 (dd, J = 8.0, 1.9 Hz, 1 H), 7.66 (ddt, J = 7.3, 5.7, 1.4 Hz, 2 H), 7.59 (ddt, J = 7.4, 5.6, 1.5 Hz, 2 H), 7.27 (s, 1 H), 7.23 (s, 1 H), 7.11 (s, 1 H), 6.90 (s, 1 H), 6.83 (d, J = 8.7 Hz, 2 H), 6.58 (d, J =2.5 Hz, 2 H), 6.34 (dd, J = 8.6, 2.6 Hz, 2 H), 3.77 (s, 6 H), 3.65 (s, 6 H), 2.29 (s, 3 H), 2.10 (s, 3 H), 1.97 (s, 3 H), 1.94 (s, 3 H). HRMS (ESI TOF) m/z: [M] 2+ Calcd for C76H63N7O6Ru ; Found Anal. Calcd for C76H63N7O6F12P2Ru H2O (%): C, 57.80; H, 4.15; N, Found: C, 57.71; H, 4.25; N, Compound IIc. Ligand 20 (257 mg, 0.24 mmol) and Ru(bpy)2Cl2 (117 mg, 0.24 mmol) were refluxed in a mixture of ethanol (15 ml) and chloroform (5 ml) under N2 for 2 days. Then the solvents were evaporated and the solid residue was subjected to chromatography on silica gel column. At first, the eluent was pure acetone, then a 9:1 (v:v) mixture of acetone and H2O, and finally a 9:1 (v:v) mixture of acetone and H2O with 1% saturated aqueous KNO3 solution was used. KPF6 was added to the desired chromatography fractions, and the acetone was removed completely on a rotary evaporator. The aqueous phase was extracted with CH2Cl2. The combined organic phases were washed with water and then evaporated to dryness. The product was obtained as a red solid (199 mg, 0.11 mmol, 47%). 1 H NMR (400 MHz, acetone-d6): [ppm] 9.00 (dd, J = 8.4, 2.5 Hz, 2 H), (m, 4 H), 8.38 (d, J = 8.0 Hz, 1 H), (m, 6 H), (m, 5 H), (m, 2 H), 8.08 (dt, J = 8.5, 2.1 Hz, 2 H), (m, 3 H), (m, 2 H), S10

11 7.58 (m, 2 H), 7.32 (s, 1 H), 7.20 (d, J = 2.4 Hz, 1 H), 7.16 (d, J = 2.6 Hz, 1 H), 7.07 (s, 1 H), 7.05 (s, 1 H), 7.04 (s, 1 H), 7.00 (s, 1 H), 6.91 (s, 1 H), 6.84 (d, J = 8.7 Hz, 2 H), 6.65 (d, J = 2.6 Hz, 2 H), 6.41 (dd, J = 8.6, 2.6 Hz, 2 H), 3.78 (s, 6 H), 3.67 (s, 6 H), 2.34 (s, 3 H), 2.09 (s, 9 H), (m, 6 H), 2.02 (s, 3 H), 1.94 (s, 3 H). HRMS (ESI TOF) m/z: [M] 2+ Calcd for C92H79N7O6Ru ; Found Anal. Calcd for C92H79N7O6F12P2Ru 2H2O (%): C, 61.20; H, 4.63; N, Found: C, 61.13; H, 4.57; N, Compound IIIc. Ligand 21 (137 mg, 0.11 mmol) and Ru(bpy)2Cl2 (52 mg, 0.11 mmol) in ethanol (18 ml) and chloroform (6 ml) were heated to reflux under N2 for 3 days. Then the solvent was evaporated, and the solid residue was purified by chromatography on silica gel column. At first, the eluent was pure acetone, then a 9:1 (v:v) mixture of acetone and H2O, and finally a 9:1 (v:v) mixture of acetone and H2O with 1% saturated aqueous KNO3 was used. KPF6 was added to the desired chromatography fractions, and the acetone was evaporated completely. The product was then extracted with CH2Cl2. The combined CH2Cl2 phases were washed with water, and then evaporated to dryness. This afforded the product as a red solid (61 mg, mmol, 29%). 1 H NMR (400 MHz, acetone-d6): [ppm] 9.01 (d, J = 8.5 Hz, 2 H), 8.90 (d, J = 8.2 Hz, 4 H), 8.39 (d, J = 8.0 Hz, 1 H), (m, 6 H), (m, 5 H), 8.19 (d, J = 5.7 Hz, 2 H), (m, 2 H), 8.01 (dd, J = 8.1, 2.0 Hz, 1 H), (m, 2 H), (m, 2 H), (m, 2 H), 7.34 (s, 1 H), (m, 2 H), 7.15 (s, 1 H), 7.11 (s, 1 H), (m, 3 H), 7.03 (s, 1 H), 7.01 (s, 1 H), 7.00 (s, 1 H), 6.96 (s, 1 H), 6.85 (d, J = 8.7 Hz, 2 H), 6.67 (d, J = 2.6 Hz, 2 H), 6.43 (dd, J = 8.6, 2.6 Hz, 2 H), 3.78 (s, 6 H), 3.68 (s, 6 H), 2.37 (s, 3 H), 2.16 (d, J = 3.5 Hz, 3 H), 2.12 (s, 3 H), (m, 24 H), 2.00 (d, J = 4.4 Hz, 3 H). HRMS (ESI TOF) m/z: [M] 2+ Calcd for C108H95N7O6Ru ; Found Anal. Calcd for C108H95N7O6F12P2Ru 2CH3(CO)CH3 (%): C, 64.83; H, 5.20; N, Found: C, 64.90; H, 5.54; N, S11

12 Equipment and methods A Bruker Avance III instrument operating at 400 MHz frequency was used for 1 H NMR spectroscopy. The instrument was equipped with a direct observe 5-mm BBFO smart probe. Mass spectra were acquired on Bruker esquire 3000 plus and Bruker maxis 4G QTOF EDI spectrometers. Ms. Sylvie Mittelheisser (Department of Chemistry at University of Basel) conducted elemental analyses on a Vario Micro Cube instrument. A Versastat3-200 potentiostat from Princeton Applied Research was employed for cyclic voltammetry. A glassy carbon disk electrode served as a working electrode, the counter electrode was a silver wire, and the reference electrode was a saturated calomel electrode (SCE). The solvent was 1:1 (v:v) CH3CN / H2O containing 0.1 KCl as an electrolyte. Potential sweeps rates were 0.1 V/s. Typical sample concentrations were 1 mm. Optical absorption spectroscopy was performed using a Cary 5000 instrument from Varian. For spectroelectrochemistry, a Pt grid electrode in a suitable quartz cuvette was used. The Pt grid electrode was connected to the abovementioned potentiostat. For oxidative spectro-electrochemistry, a potential of 0.8 V vs. SCE was applied. Reductive spectro-electrochemistry was performed while applying a potential of -0.9 V vs. SCE. An LP920-KS instrument from Edinburgh Instruments was used for transient absorption spectroscopy. The frequencydoubled output of a Quantel Brilliant b laser served as an excitation source. The laser pulse duration was 10 ns and the pulse frequency was 10 Hz. The typical pulse energy used for transient absorption studies was 15 mj. Detection of transient absorption spectra occurred on an iccd camera from Andor. Single-wavelength kinetics were recorded using a photomultiplier tube. All optical spectroscopic experiments were performed under deaerated conditions using quartz cuvettes in which oxygen can be removed by the freeze-pump-thaw technique. Transient absorption spectra in the NIR spectral range (for compounds Ic IIIc) were recorded using the data slicing mode and the NIR 301/2 detector from Edinburgh Instruments. S12

13 Cyclic voltammetry Figure S1. Cyclic voltammograms for (a) Ia IIIa, (b) Ib IIIb, and (c) Ic IIIc in 1:1 (v:v) CH3CN / H2O. The voltage sweep rate was 0.1 V/s, the reference electrode was SCE, 0.1 M KCl was used as a supporting electrolyte. Red traces: triads with n = 1, blue traces: triads with n = 2, green traces: triads with n = 3. S13

14 Figure S2. Cyclic voltammograms for (a) Ia IIIa, (b) Ib IIIb, and (c) Ic IIIc in neat CH3CN. The voltage sweep rate was 0.1 V/s, the reference electrode was SCE, 0.1 M TBAPF6 was used as a supporting electrolyte. Red traces: triads with n = 1, blue traces: triads with n = 2, green traces: triads with n = 3. S14

15 Energy level scheme for photoinduced charge-separation reactions Figure S3. Generic energy level scheme for all 9 triads in (a) 1:1 (v:v) CH3CN / H2O and (b) in neat CH3CN, based on the redox potentials from Table 1 / Figure S1 / Figure S2. For 1:1 (v:v) CH3CN / H2O solution, E 0 (Ru 3+/2+ ) = 1.02 V vs. SCE, E 0 (Ru 2+/+ ) = V vs. SCE, and EMLCT = 2.12 ev were used as input values. 4 For neat CH3CN, E 0 (Ru 3+/2+ ) = 1.38 V vs. SCE, E 0 (Ru 2+/+ ) = V vs. SCE, and EMLCT = 2.12 ev were employed. S15

16 Spectro-electrochemical data Figure S4. Spectro-electrochemical UV-Vis difference spectra for Ia IIIa in 1:1 (v:v) CH3CN / H2O measured after different time intervals following application of potentials of +0.8 V (left) and -0.9 V vs. SCE (right), leading to the formation of TAA + (left) and AQ - (right), respectively. UV-Vis spectra prior to applying any potential served as baselines. Sample concentrations were 0.1 mm. S16

17 Figure S5. Spectro-electrochemical UV-Vis difference spectra for Ib IIIb in 1:1 (v:v) CH3CN / H2O measured after different time intervals following application of potentials of +1.0 V (left) and -0.9 V vs. SCE (right), leading to the formation of TAA + (left) and AQ - (right), respectively. UV-Vis spectra prior to applying any potential served as baselines. Sample concentrations were 0.1 mm. S17

18 Figure S6. Spectro-electrochemical UV-Vis difference spectra for Ic IIIc in 1:1 (v:v) CH3CN / H2O measured after different time intervals following application of potentials of V (left) and -0.9 V vs. SCE (right), leading to the formation of TAA + (left) and AQ - (right), respectively. UV-Vis spectra prior to applying any potential served as baselines. Sample concentrations were 0.1 mm. S18

19 Transient absorption data for compound ref Figure S7. Temporal evolution of the transient absorption signals for compound ref at (a) 410 nm and (b) 560 nm, and luminescence decay of compound ref (c) detected at 620 nm. Excitation occurred at 532 nm with laser pulses of 10 ns duration in all cases, the solvent was 1:1 (v:v) CH3CN / H2O at 20 C. All decays have been normalized to 1.0 at t = 0. S19

20 Temperature-dependence studies and activation free energies Table S1. Time constants extracted from transient absorption decays measured for compounds Ia IIIa in 1:1 (v:v) CH3CN / H2O at different wavelengths ( ) and temperatures. Excitation occurred at 532 nm with laser pulses of 10 ns duration. All time constants are in units of nanoseconds. compound Ia compound IIa compound IIIa T [ C] 380nm 510nm 770nm 380nm 510nm 770nm 380nm 510nm 770nm Table S2. Time constants extracted from transient absorption decays measured for compounds Ib IIIb in 1:1 (v:v) CH3CN / H2O at different wavelengths ( ) and temperatures. Excitation occurred at 532 nm with laser pulses of 10 ns duration. All time constants are in units of nanoseconds. compound Ib compound IIb compound IIIb T [ C] 360nm 510nm 710nm 360nm 510nm 710nm 360nm 510nm 710nm S20

21 Table S3. Time constants extracted from transient absorption decays measured for compounds Ic IIIc in 1:1 (v:v) CH3CN / H2O at different wavelengths ( ) and temperatures. Excitation occurred at 532 nm with laser pulses of 10 ns duration. All time constants are in units of nanoseconds. compound Ic compound IIc compound IIIc T [ C] 375nm 510nm 950nm 375nm 510nm 950nm 375nm 510nm 950nm N/A N/A N/A N/A N/A N/A N/A S21

22 Figure S8. Arrhenius plots for thermal electron transfer from AQ - to TAA + in the 3 triad series in deaerated 1:1 (v:v) CH3CN / H2O based on the data in Tables S1 S3. (a) Ia, (b) IIa, (c) IIIa, (d) Ib, (e) IIb, (f) IIIb, (g) Ic, (h) IIc, (i) IIIc. S22

23 Absorption of AQ - in 1:1 (v:v) CH3CN / H2O vs. neat CH3CN Figure S9. Transient absorption spectra for Ia IIIa in 1:1 (v:v) CH3CN / H2O (solid traces, left y-axes) and in neat CH3CN (dashed traces, right y-axes) obtained after excitation at 532 nm with laser pulses of 10 ns duration. All spectra were recorded by time-integration over an interval of 200 ns, using delay times as follows: (a) no delay; (b) no delay for solid trace, 100 ns for dashed trace; (c) 3 s for solid trace, 2 s for dashed trace. S23

24 Determination of electronic coupling matrix elements (HDA) Figure S10. Plots of ln(ket T 1/2 ) versus 1/T for the 9 triads in 1:1 (v:v) CH3CN / H2O based on the data from Tables S1 S3. (a) Ia IIIa; (b) Ib IIIb; (c) Ic IIIc. Red symbols: triads with n = 1; blue symbols: triads with n = 2; green symbols: triads with n = 3. The HDA values reported in Table 4 of the main paper were determined from the intercepts of linear regression fits to these plots. 5 S24

25 Reactant and product potential energy wells Figure S11. Reactant (black) and product (red) potential energy wells illustrating the changeover from inverted (left) to activationless (middle) to normal (right) electron transfer as a function of distance (rda) between AQ - and TAA + in compounds Ib, IIb, and IIIb. The driving-force ( GET 0 ) stays nearly constant (Table 1 of the main paper), and the changeover is essentially due to increasing reorganization energy ( ) with increasing rda (Table 3 of the main paper). The lower half of the figure shows zooms of the key regions from the upper half. S25

26 Figure S12. Reactant (black) and product (red) potential energy wells illustrating the changeover from inverted (left) to activationless (middle) to normal (right) electron transfer as a function of distance (rda) between AQ - and TAA + in compounds Ic, IIc, and IIIc. The driving-force ( GET 0 ) stays nearly constant (Table 1 of the main paper), and the changeover is essentially due to increasing reorganization energy ( ) with increasing rda (Table 3 of the main paper). The lower half of the figure shows zooms of the key regions from the upper half. S26

27 References (1) Kuss-Petermann, M.; Wenger, O. S., Angew. Chem. Int. Ed. 2016, doi: /anie (2) Bai, X. L.; Liu, X. D.; Wang, M.; Kang, C. Q.; Gao, L. X., Synthesis 2005, 458. (3) (a) Hensel, V.; Lutzow, K.; Jacob, J.; Gessler, K.; Saenger, W.; Schlüter, A. D., Angew. Chem. Int. Ed. 1997, 36, (b) Hensel, V.; Schlüter, A. D., Liebigs Ann. 1997, 303. (4) Roundhill, D. M., Photochemistry and Photophysics of Metal Complexes. Plenum Press: New York, (5) Sukegawa, J.; Schubert, C.; Zhu, X. Z.; Tsuji, H.; Guldi, D. M.; Nakamura, E., Nature Chem. 2014, 6, 899. S27