# Self-Assembled Multinuclear Complexes for Cobalt(II/III) Mediated Sensitized Solar Cells
## 2 Experimental Section
### Synthesis  
4_4'_-bis(trimethylaminomethyl)2,2'bipyridine (TMAM) (Figure S1a): briefly, trimethylamine (54.47 mL) was added dropwise to a suspension of 4-4'-bis(bromomethyl)-2-2'-bipyridine (8.76 g 2.6 mmol) in ethanol (300 mL), the solution became light pink and a white solid was filtered off, washed with water, and dried [14,15]. (\({}^{\text{t}}\)H NMR (400 MHz, Acetonitrile-d\({}_{3}\), 8 ppm): 8.88 (dd, \(J\) = 5.0, 0.8 Hz, 2H), 8.62 (dd, \(J\) = 1.9, 0.8 Hz, 2H), 7.60 (dd, \(J\) = 5.0, 1.8 Hz, 2H), 4.55 (s, 4H), 3.13 (s, 18H)). (Figure S2). [Ru(TMAM)\({}_{2}\)Cl\({}_{2}\)](PF\({}_{6}\))\({}_{4}\) (Figure S1b): the TMAM ligand (1 g 1.17 mmol) and the dimer dichlor(p-cymene)-ruthenium(II) (0.260 g 0.425 mmol) were dissolved in 35 mL of DMF, and heated with a microwave reactor at 150 \({}^{\circ}\)C for 25 min in an open flask fitted with a reflux condenser. DMF was evaporated to dryness and a dark violet solid was obtained. This intermediate complex was used without purification. **1** ([Ru(TMAM)\({}_{2}\)CN\({}_{2}\)](TFSI)\({}_{4}\)), (Ru(TMAM)) (Figure S1c): KCN (1 g, 15 mmol 80 eq) and Ru(TMAM)\({}_{2}\)Cl\({}_{2}\)](PF\({}_{6}\))\({}_{4}\) (260 mg 0.19 mmol, 1 eq) were reacted in 13 mL of water in a microwave reactor for 5 min at 100 \({}^{\circ}\)C under atmospheric pressure. The product was first precipitated with an excess of LiTFSI, re-dissolved in the minimum amount of ACN, and re-precipitated by the addition of an excess volume of diethyl ether. The **1** (Ru(TMAM)) was loaded in a Sephadex LH-20 column and eluted with methanol. An orange solid was obtained following rotary evaporation. (\({}^{\text{t}}\)H NMR (400 MHz, Acetone-d\({}_{6}\), 8 ppm): 10.00 (d, \(J\) = 5.8 Hz, 2H), 8.87 (s, 2H), 8.83 (s, 2H) 8.13 (d, \(J\) = 5.7 Hz, 2H), 7.99 (d, \(J\) = 6.0 Hz, 2H), 7.65 (dd, \(J\) = 5.7, 1.7 Hz, 2H), 5.06-4.86 (m, 8H), 3.49 (s, 18H), 3.39 (s, 18H). \({}^{\text{t}}\)C NMR (400 MHz, Acetone-d6, 8 ppm): 157.63, 157.69, 155.55, 151.18, 149.65, 136.85, 135.92, 130.30, 127.09, 126.66, 66.92, 66.61, 52.91, 52.80) (Figures S3 and S4) (Figure S5, ESI-MS). **2** (Ru(TMAM))-Ag\({}^{+}\)) (Figure S1d): This compound was obtained by mixing AgNO\({}_{3}\) and **1** (Ru(TMAM)) in a 1:1 ratio in either ethanol or methanol. (\({}^{\text{t}}\)H NMR (400 MHz, DMSO-d\({}_{6}\), 8 ppm): 9.63 (1H), 8.68 (1H), 8.61 (1H), 7.92 (1H), 7.82 (1H), 7.47 (1H), 4.74 (2H), 4.55 (2H), 3.23 (9H), 3.08 (9H). \({}^{\text{t}}\)\({}^{\text{was fabricated by spincoating (10 s at 1000 rpm, 2 s at 2000 rpm) a 0.3 M titanium tetraiso-propoxide solution in 1-butanol, followed by drying at room temperature, and heating in air at 500 \({}^{\circ}\)C for 15 min. The TiO\({}_{2}\) colloidal paste for the porous nanocrystalline film was applied on top of the blocking layer by manually spreading the TiO\({}_{2}\) paste by sliding a glass blade over two strips of 3M scotch tape placed at an interdistance of 0.5 cm. The wet films were thermally treated according to the following temperature program: from RT to 120 \({}^{\circ}\)C at 10 \({}^{\circ}\)C/min, from 120 \({}^{\circ}\)C to 450 \({}^{\circ}\)C at 11 \({}^{\circ}\)C/min, rest at 450 \({}^{\circ}\)C for additional 30 min followed by ramping at 500 \({}^{\circ}\)C at 5 \({}^{\circ}\)C/min, and resting at 500 \({}^{\circ}\)C for 10 min. Cooling at RT occurred naturally. TiCl\({}_{4}\) treatment of the sintered TiO\({}_{2}\) films was performed by drop casting 0.4 M TiCl\({}_{4}\) followed by overnight hydrolysis at room temperature in a closed chamber. A final treatment at 450 \({}^{\circ}\)C for 30 min in air was instrumental in consolidating the TiO\({}_{2}\) overlayer created on top of the titania nanoparticles upon slow hydrolysis of TiCl\({}_{4}\). The typical thickness of the resulting film was of the order of 8 \(\upmu\)m [20].