High Extinction Coefficient Ru-Sensitizers that Promote Hole Transfer on Nanocrystalline TiO2
Journal article, 2014
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.
V353
METAL-COMPLEXES
THIN-FILM
extinction coefficients
I-I BONDS
SOLAR-CELLS
EGAN B
1991
ELECTROCHEMISTRY
dye-sensitized solar cells
charge transfer
RUTHENIUM(II) COMPLEXES
Ruthenium
hole transfer
NATURE
P737
LIGANDS
ELECTRON-TRANSFER
EXCITED-STATES
PHOTOPHYSICAL PROPERTIES
Author
Maria Abrahamsson
Chalmers, Chemical and Biological Engineering, Physical Chemistry
Joachim Hedberg
Chalmers, Chemical and Biological Engineering, Physical Chemistry
Hans-Christian Becker
Uppsala University
A. Staniszewski
Johns Hopkins University
W. H. Pearson
US Naval Academy
W. B. Heuer
US Naval Academy
G. J. Meyer
Johns Hopkins University
ChemPhysChem
1439-4235 (ISSN) 1439-7641 (eISSN)
Vol. 15 6 1154-1163Areas of Advance
Energy
Materials Science
Subject Categories
Chemical Sciences
DOI
10.1002/cphc.201301193