title: A new strategy for the improvement of photophysical properties in ruthenium(II) polypyridyl complexes. Synthesis and photophysical and electrochemical characterization of six mononuclear ruthenium(II) bisterpyridine-type complexes.
abstract: The synthesis and characterization of six ruthenium(II) bistridentate polypyridyl complexes is described. These were designed on the basis of a new approach to increase the excited-state lifetime of ruthenium(II) bisterpyridine-type complexes. By the use of a bipyridylpyridyl methane ligand in place of terpyridine, the coordination environment of the metal ion becomes nearly octahedral and the rate of deactivation via ligand-field (i.e., metal-centered) states was reduced as shown by temperature-dependent emission lifetime studies. Still, the possibility to make quasi-linear donor-ruthenium-acceptor triads is maintained in the complexes. The most promising complex shows an excited-state lifetime of tau = 15 ns in alcohol solutions at room temperature, which should be compared to a lifetime of tau = 0.25 ns for [Ru(tpy)2]2+. The X-ray structure of the new complex indeed shows a more octahedral geometry than that of [Ru(tpy)2]2+. Most importantly, the high excited-state energy was retained, and thus, so was the potential high reactivity of the excited complex, which has not been the case with previously published strategies based on bistridentate complexes.
authors.affiliation: Department of Physical Chemistry, Uppsala University, Box 579, 751 23 Uppsala, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Abrahamsson
authors.forename: Henriette
authors.initials: H
authors.lastname: Wolpher
authors.forename: Olof
authors.initials: O
authors.lastname: Johansson
authors.forename: Jan
authors.initials: J
authors.lastname: Larsson
authors.forename: Mikael
authors.initials: M
authors.lastname: Kritikos
authors.forename: Lars
authors.initials: L
authors.lastname: Eriksson
authors.forename: Per-Ola
authors.initials: PO
authors.lastname: Norrby
authors.forename: Jonas
authors.initials: J
authors.lastname: Bergquist
authors.forename: Licheng
authors.initials: L
authors.lastname: Sun
authors.forename: Björn
authors.initials: B
authors.lastname: Akermark
authors.forename: Leif
authors.initials: L
authors.lastname: Hammarström