Cyclometalated Ru() complexes with tunable redox and optical properties for dye-sensitized solar cells

Cyclometalated Ru( ii ) complexes with 2-arylbenzimidazole antenna ligands bearing electron-donor/withdrawing substituents and anchoring 4,4′-dimethoxycarbonyl-2,2′-bipyridine have been prepared and their structure, optical and electrochemical properties have been studied. The complexes possess enhanced light-harvesting characteristics compared to those of the standard N719 dye and absorb light up to 750 nm. In addition, they demonstrate reversible redox behavior with Ru 3+ /Ru 2+ potentials being finely tuned by the change of the electron-donating ability of cyclometalated ligands. After a mild hydrolysis of dimethoxycarbonyl groups the excellent optical properties of the complexes remain unchanged and they show good efficiency when tested in dye-sensitized solar cells. Cyclometalated Ru( ii ) complexes with 2-arylbenzimidazoles demonstrate enhanced light-harvesting properties and good characteristics in dye-sensitized solar cells.