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Competition between energy transfer and interligand electron transfer in porphyrin - Osmium(II) Bis(2,2′:6′,2″-terpyridine) dyads

Lookup NU author(s): Professor Andrew Benniston, Emeritus Professor Anthony Harriman, Consuelo Pariani, Craig Sams


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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.

Publication metadata

Author(s): Benniston AC, Harriman A, Pariani C, Sams CA

Publication type: Article

Publication status: Published

Journal: Journal of Physical Chemistry A

Year: 2007

Volume: 111

Issue: 37

Pages: 8918-8924

ISSN (print): 1089-5639

ISSN (electronic): 1520-5215

Publisher: American Chemical Society


DOI: 10.1021/jp0734326


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