A Heteroleptic Bis(tridentate) Ruthenium(II) Platform Featuring an Anionic 1,2,3-Triazolate-Based Ligand for Application in the Dye-Sensitized Solar Cell

A series of bis(tridentate) ruthenium(II) complexes featuring new anionic 1,2,3-triazolate-based tridentate ligands and 2,2':6',2''-terpyridine is presented. For a complex equipped with carboxy anchoring groups, the performance in a dye-sensitized solar cell is evaluated. The title complexes are readily synthesized and can be decorated with alkyl chains utilizing azide-alkyne cycloaddition methods, in order to improve the device stability and allow the use of alternative electrolytes. On account of the strong electron donation from the 1,2,3-triazolates, the complexes exhibit a broad metal-to-ligand charge-transfer absorption (up to 700 nm), leading to an electron transfer toward the anchoring ligand. The lifetimes of the charge-separated excited states are in the range of 50 to 80 ns. In addition, the ground- and excited-state redox potentials are appropriate for the application in dye-sensitized solar cells, as demonstrated by power conversion efficiencies of up to 4.9% (vs 6.1% for N749).