| Abstract
| - The compounds Ru(bpy)2(BTL)(PF6)2 and Ru(deeb)2(BTL)(PF6)2, where bpy is 2,2′-bipyridine, deeb is 4,4′-(C2H5CO2)2-bpy, and BTL is 9′-[4,5-bis(cyanoethylthio)]-1,3-dithiol-2-ylidene]-4′,5′-diazafluorene, were found to have very high extinction coefficients in the visible region. In an acetonitrile solution, the extinction of Ru(deeb)2(BTL)(PF6)2 was ϵ = 44 000 ± 1000 M−1 cm−1 at λ = 470 nm. Two quasi-reversible oxidation waves, E1/2 = +0.88 and +1.16 V, and an irreversible reduction, Epr = −1.6 V, were observed versus ferrocene (Fc+/0). At −40 °C, a state was observed with spectroscopic properties characteristic of a metal-to-ligand charge-transfer excited state, τ = 25 ns. This same compound was found to photoinject electrons into TiO2 with a quantum yield Φ = 0.3 ± 0.2 for 532.5 or 417 nm light excitation in a 0.1 M LiClO4/acetonitrile electrolyte. In regenerative solar cells, a sustained photocurrent was observed with a maximum incident photon-to-current efficiency of 0.4. The photocurrent action and absorptance spectra were in good agreement, consistent with injection from a single excited state.
- Ruthenium(II) bipyridine dithioline compounds with extremely high extinction coefficients in the visible region were synthesized and characterized. The compound shown was found to photoinject electrons into TiO2 and support intramolecular hole transfer away from the ruthenium center.
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