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Lookup NU author(s): Professor Andrew Benniston,
Emeritus Professor Anthony Harriman,
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Rapid intramolecular energy transfer occurs from a free-base porphyrin to an attached osmium(II) bis(2,2′:6′,2″-terpyridine) complex, most likely by way of the Förster dipole - dipole mechanism. The initially formed metal-to-ligand, charge-transfer (MLCT) excited-singlet state localized on the metal complex undergoes very fast intersystem crossing to form the corresponding triplet excited state (3MLCT). This latter species transfers excitation energy to the 3π,π* triplet state associated with the porphyrin moiety, such that the overall effect is to catalyze intersystem crossing for the porphyrin. Interligand electron transfer (ILET) to the distal terpyridine ligand, for which there is no driving force, competes poorly with triplet energy transfer from the proximal 3MLCT to the porphyrin. Equipping the distal ligand with an ethynylene residue provides the necessary driving force for ILET and this process now competes effectively with triplet energy transfer to the porphyrin. The rate constants for all the relevant processes have been derived from laser flash photolysis studies. © 2007 American Chemical Society.
Author(s): Benniston AC, Harriman A, Pariani C, Sams CA
Publication type: Article
Publication status: Published
Journal: Journal of Physical Chemistry A
ISSN (print): 1089-5639
ISSN (electronic): 1520-5215
Publisher: American Chemical Society
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