Electronic Supplementary Material (ESI) for Chemical Communications This journal is © The Royal Society of Chemistry 2014 Electronic Supporting Information A mononuclear cobalt complex with organic ligand acting as precatalyst for efficient visible light-driven water oxidation Shao Fu a, Yongdong Liu a, Yong Ding a, b *, Xiaoqiang Du a, Fangyuan Song a , Rui Xianga, Baochun Ma a * a Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China. b State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 * To whom correspondence should be addressed. E-mail addresses: [email protected]; [email protected] 1 Electronic Supplementary Material (ESI) for Chemical Communications This journal is © The Royal Society of Chemistry 2014 Experimental and calculation Quantum yield calculation -1 -1 Initial O2 formation rate = 6.10 μmol∙min = 0.102 μmol∙s Irradiation radius = 1 cm = 0.01 m 2 -2 -1 -1 Photon flux = π× (0.01m) ×1686 μmol∙m ∙s = 0.529 μmol∙s initial O formation rate ( ) = 2 × × 100% photon2 flux ΦQY2 ×initial0.102 mol · s = × 100% 0. mol · s −1 µ = 38.6% −1 529µ Materials: N,N'-Bis(salicylidene)ethylenediaminecobalt (II) (99 %) was purchased from Aldrich. 2, 2’, 2’’-Triaminotriethylamine (TREN, 97%) was from STREM CHEMICALS. Meso-Tetra(4-carboxyphenyl)porphine (TCPP) was from the Frontier Scientific. Purified water (18.2 MΩ cm) for the preparation of solutions was obtained from a Milli-Q system (Millipore, Direct-Q 3 UV), and all other chemicals and salts used were of the highest purity available from commercial sources. Preparation of different kinds of photosensitizers Synthesis of [Ru(bpy)3]Cl2∙6H2O o Commercial RuCl3·xH2O is dried in an oven at 120 C for 3 h. It is then finely ground in a mortar and returned to the oven for a further 1h prior to use. It is convenient to store the “dried” RuCl3 at this temperature. “Dried” RuCl3 (0.4 g, 1.93 mmol), 2, 2’-bipyridine (0.9 g, 5.76 mmol), and water (40 mL) are placed in a 100 mL flask fitted with a reflux condenser. Freshly prepared sodium phosphinate (sodium hypophosphite) solution (2 mL) is added and the mixture heated at the boil for 30 min. [The sodium phosphinate solution is prepared by the careful addition of sodium hydroxide pellets to about 2 mL of 31% phosphinic acid (hypophosphorous acid) until a slight cloudy precipitate is obtained. Phosphinic acid is then added dropwise, until the precipitate just redissolves.] 2 Electronic Supplementary Material (ESI) for Chemical Communications This journal is © The Royal Society of Chemistry 2014 During reflux, the initial green solution changes to brown and finally orange. It is filtered to remove traces of undissolved material and potassium chloride (12.6 g) added to the filtrate to precipitate the crude product. The solution and solid are then heated at the boil to give a deep-red solution, which on cooling to room temperature yields beautiful, red plate-like crystals. These are filtered off, and air-dried. The yield is 1.05g (73%). The product could be recrystallized from boiling water (~2.8 mL∙g-1) and then air-dried. Properties: Aqueous solution of [Ru(bpy)3]Cl2∙6H2O have two characteristic absorption maxima at 428 nm (shoulder ε = 11,700 dm3∙mol-1∙cm-1) and 452nm (ε = 14,000 dm3∙mol-1∙cm-1), which have been assigned to metal ligand charge-transfer transitions. Synthesis of [Ru(bpy)3]SO4 [Ru(bpy)3]SO4 was synthesized according to reference 1. 1 equiv of Ag2SO4 was added to an aqueous solution of [Ru(bpy)3]Cl2 and stirred vigorously for 1 hour. Solid and liquid were separated by filtration. After evaporation of the aqueous solution under reduced pressure, orange solid photosensitizer was obtained. Synthesis of [Ru(bpy)3](ClO4)2 [Ru(bpy)3](ClO4)2 was synthesized according to reference 2. [Ru(bpy)3](ClO4)2 was prepared by adding 4 M HClO4 to an aqueous solution of [Ru(bpy)3]Cl2 and then separated by filtration. Synthesis of [Ru(bpy)3](ClO4)3 [Ru(bpy)3](ClO4)3 was prepared according to reference 3. The salt of [Ru(bpy)3](ClO4)2 was dissolved in 0.5 M H2SO4. A scoop of PbO2 was added, and the solution was stirred at room temperature and filtered through a fine frit. The perchlorate concentration of the filtrate was adjusted to ~ 2 M by the dropwise addition of HClO4, and the solution was then cooled in an ice bath. Green crystals of [Ru(bpy)3](ClO4)3 rapidly formed and were recrystallized from 4 M o HClO4 at 0 C. Preparation of various cobalt complexes III II Syntesis of K7[Co Co (H2O)W11 O39]∙15H2O The synthesis was seen reference 4. 19.8 g (0.06 mol) of Na2WO4∙2H2O was dissolved in 40 mL of H2O. This solution was adjusted to pH between 6.5 and 7.5 by the slow addition of 4 mL of glacial acetic acid before heated to near boiling. A solution containing 2.5 g (0.01 mol) of Co(OAc)2∙4H2O in 13 mL of H2O was then added dropwise to the above system with stirring. 3 Electronic Supplementary Material (ESI) for Chemical Communications This journal is © The Royal Society of Chemistry 2014 After the Co(OAc)2 solution had been added, the mixture was heated to reflux for 10 min and then filtered while still hot to remove trace of insoluble material. This solution was heated to 80 oC, and 7 g of K2S2O8 was slowly added in small amounts. During the addition, a large amount of gas generated instantaneously. When addition is completed, the solution was heated to boiling. The color changed from green to deep dark brown finally. The result mixture was boiled for 5 more minutes, filtered hot and then heated to boiling again. 25 mL of hot saturated KNO3 solution was added. This mixture was then cooled in an ice bath, brown precipitate formed rapidly. Fine dark brown particle solid was obtained after filtered. This solid was added to a beaker containing appropriate amount of water and then heated in 90 oC hot water bath. The mixture was stirred for few minutes, filtered and filtrate was collected. Sludge solid continually precipitated from the filtrate solution in cooling process. Removing this sludge by filtration several times until a clear brown solution obtained. The well-formed dark brown cubic single crystals formed in two weeks after evaporation at room temperature. Yield: 2.5 g (15%). Single crystals suitable for X-ray crystallography were obtained by filtration. Thermogravimetric analysis (TGA) gave 15 water molecules of hydration. FT-IR (cm-1): 953 (sh), 891 (s), 795 (s), 748 (m), 668 (m), 524 (w), 478 3 -1 -1 (w), 424 (sh). UV-Vis (H2O, pH 7.0): λmax, 387 nm (ε387 = 1580 dm ∙mol ∙cm ). Elemental III II analysis calculated (%) for K7[Co Co (H2O)W11O39]∙15H2O: K, 8.23; Co, 3.54; W, 60.80. Found: K, 8.18; Co, 3.56; W, 60.12. III II Fig. S1 FT-IR spectrum of K7[Co Co (H2O)W11O39]∙15H2O. Synthesis of Na10[Co4(H2O)2(PW9O34)2]∙25H2O Na10[Co4(H2O)2(PW9O34)2] was synthesized according to reference 5. Na2WO4·2H2O 4 Electronic Supplementary Material (ESI) for Chemical Communications This journal is © The Royal Society of Chemistry 2014 (35.62 g, 0.108 mol), Na2HPO4·7H2O (3.22 g, 0.012 mol), and Co(NO3)2·6H2O (6.98 g, 0.024 mol) were mixed in 100 mL water. After adjusting the pH from 9 to 7, this purple suspension was then refluxed at 100 oC for 3 hours. A dark purple solution resulted within minutes of heating. After reflux, the solution was saturated with NaCl and allowed to cool to room temperature. The resulting purple crystals were collected, quickly washed with approximately 40 mL of water, and recrystallized from hot water (31% mass yield based on Co). Thermogravimetric analysis gave 25 water molecules of hydration. FT/IR (cm-1): 1039 (m), 941 (m), 890 (w), 807 (w), 750 (w). 3 -1 -1 UV-Vis (H2O, pH 3.5 to 9): λmax, 580 nm (ε579 = 330 dm ·mol ·cm ). Elemental analysis calculated (%) for Na10[Co4(H2O)2(PW9O34)2]·25H2O: Co, 4.36; Na, 4.25; P, 1.14; W, 61.15. Found: Co, 4.33; Na, 4.18; P, 1.20; W, 60.48. Fig. S2 FT-IR spectrum of Na10[Co4(H2O)2(PW9O34)2]∙25H2O. Synthesis of N,N’-disalicylal-1,2-phenylenediamine: Salophen (Slp) ligand N N OH HO The synthesis was according to reference 6. o-Phenylenediamine (108 mg, 1 mmol) and salicyaldehyde (256 mg, 2.1 mmol) were refluxed for 5 h at 78 oC in 100 mL of absolute ethanol in the presence of a few drops of acetic acid. The mixture turned orange immediately. The product was collected by filtration as orange crystals after the mixture evaporated to a smaller volume 1 under reduced pressure. (77% yield). H NMR: (CDCl3) 6.90−7.39 (m, 12H), 8.64 (s, 2H), 13.07 5 Electronic Supplementary Material (ESI) for Chemical Communications This journal is © The Royal Society of Chemistry 2014 (s, 2H). Fig. S3 1H NMR spectrum of Slp. Synthesis of Co-Salophen (CoSlp) N N Co O O CoSlp was synthesized according to reference 7. In a 50 mL round-bottom flask 240 mg (0.759 mmol) of Slp was dissolved in 18 mL of methanol.