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Selective Triplet-State Formation during Charge Recombination in a Fullerene/Bodipy Molecular Dyad (Bodipy=Borondipyrromethene)

Lookup NU author(s): Dr Ben Allen, Dorota Rewinska, Emeritus Professor Anthony Harriman


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A conformationally restricted molecular dyad has been synthesized and subjected to detailed photophysical examination. The dyad comprises a borondipyrromethene (Bodipy) dye covalently linked to a buckminsterfullerene C-60 residue, and is equipped with hexadecyne units at the boron centre in order to assist solubility. The linkage consists of a diphenyltolane. attached at the meso position of the Bodipy core and through an N-methylpyrrolidine ring at the C-60 surface. Triplet states localised on the two terminals are essentially isoenergetic. Cyclic voltammetry indicates that light-induced electron transfer from Bodipy to C-60 is thermodynamically favourable and could compete with intramolecular energy transfer in the same direction. The driving force for light-induced electron abstraction from Bodipy by the singlet excited state of C-60 depends critically on the solvent polarity. Thus, in non-polar solvents, light-induced electron transfer is thermodynamically uphill, but fast excitation energy transfer occurs from Bodipy to C-60 and is followed by intersystem crossing and subsequent equilibration of the two triplet excited states. Moving to a polar solvent switches on light-induced electron transfer. Now, in benzonitrile, the charge-transfer state (CTS) is positioned slightly below the triplet levels., such that charge recombination restores the ground state. However, in CH2Cl2 or methyltetrahydrofuran, the CTS is slightly higher in energy than the triplet levels, and decays, in part, to form the triplet state localized on the C-60 residue. This step is highly specific and does not result in direct formation of the triplet excited state localized on the Bodipy unit. Subsequent equilibration of the two triplets takes place on a relatively slow timescale.

Publication metadata

Author(s): Ziessel R, Allen BD, Rewinska DB, Harriman A

Publication type: Article

Publication status: Published

Journal: Chemistry: A European Journal

Year: 2009

Volume: 15

Issue: 30

Pages: 7382-7393

ISSN (print): 0947-6539

ISSN (electronic): 1521-3765

Publisher: Wiley - VCH Verlag GmbH & Co. KGaA


DOI: 10.1002/chem.200900440


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Funder referenceFunder name
Universite Louis Pasteur de Strasbourg
University of Newcastle