High Extinction Coefficient Ru-Sensitizers that Promote Hole Transfer on Nanocrystalline TiO2
2014 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 6, 1154-1163 p.Article in journal (Refereed) Published
Two series of Ru-II polypyridyl compounds with formulas [(bpy)(2)RuL](PF6)(2) and [(deeb)(2)RuL](PF6)(2), where bpy is 2,2-bipyridine, deeb is 4,4-diethylester-2,2-bpy, and L is one of several substituted 9-(1,3-dithiole-2-ylidene)-4,5-diazafluorene ligands, were studied as potential photosensitizers for TiO2. These compounds possess notably high extinction coefficients (40000M(-1)cm(-1) @470 nm) which are shown by time-dependent density functional theory (TD-DFT) calculations to result from overlapping metal-to-ligand charge transfer (MLCT) and ligand-localized transitions. Low-temperature absorption and photoluminescence measurements were suggestive of a short-lived MLCT excited state. When adsorbed onto TiO2 thin films, both the free ligands (L) and their corresponding [(deeb)(2)RuL](2+) complexes exhibited rapid excited-state electron injection into TiO2; in the case of the complexes, this was followed by rapid (k>10(8) s(-1)) hole transfer from Ru-III to the 1,3-dithiole ring of the L ligand. Observation of diffusion-limited reductive quenching of the [Ru(bpz)(3)](2+)* (bpz is 2,2-bipyrazine) excited state by the L ligands in solution supported the occurrence of intramolecular hole transfer following electron injection by the TiO2-anchored complexes.
Place, publisher, year, edition, pages
2014. Vol. 15, no 6, 1154-1163 p.
charge transfer, dye-sensitized solar cells, extinction coefficients, hole transfer, Ruthenium
IdentifiersURN: urn:nbn:se:uu:diva-225022DOI: 10.1002/cphc.201301193ISI: 000334080700021OAI: oai:DiVA.org:uu-225022DiVA: diva2:719546