title: Photochemical Bleaching of an Elaborate Artificial Light-Harvesting Antenna.
abstract: The target artificial light-harvesting antenna, comprising 21 discrete chromophores arranged in a logical order, undergoes photochemical bleaching when dispersed in a thin plastic film. The lowest-energy component, which has an absorption maximum at 660 nm, bleaches through first-order kinetics at a relatively fast rate. The other components bleach more slowly, in part, because their excited-state lifetimes are rendered relatively short by virtue of fast intramolecular electronic energy transfer to the terminal acceptor. Two of the dyes, these being close to the terminal acceptor but interconnected through a reversible energy-transfer step, bleach by way of an autocatalytic step. Loss of the terminal acceptor, thereby switching off the energy-transfer route, escalates the rate of bleaching of these ancillary dyes. The opposite terminal, formed by a series of eight pyrene-based chromophores, does not bleach to any significant degree. Confirmation of the various bleaching steps is obtained by examination of an antenna lacking the terminal acceptor, where the autocatalytic route does not exist and bleaching is very slow.
authors.affiliation: Molecular Photonics Laboratory, School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU (United Kingdom).
authors.forename: Mohammed A H
authors.initials: MA
authors.lastname: Alamiry
authors.affiliation: Molecular Photonics Laboratory, School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU (United Kingdom). anthony.harriman@ncl.ac.uk.
authors.forename: Anthony
authors.initials: A
authors.lastname: Harriman
authors.affiliation: Institut de Chimie et Procédés pour l'Energie l'Environnement et la Santé (ICPEES), Laboratoire de Chimie Moléculaire et Spectroscopies Avancées (LCOSA), UMR 7515 au CNRS, Ecole Européenne de Chimie, Polymères et Matériaux, 25 rue Becquerel, 67087 Strasbourg Cedex 02 (France).
authors.forename: Alexandre
authors.initials: A
authors.lastname: Haefele
authors.affiliation: Institut de Chimie et Procédés pour l'Energie l'Environnement et la Santé (ICPEES), Laboratoire de Chimie Moléculaire et Spectroscopies Avancées (LCOSA), UMR 7515 au CNRS, Ecole Européenne de Chimie, Polymères et Matériaux, 25 rue Becquerel, 67087 Strasbourg Cedex 02 (France). ziessel@unistra.fr.
authors.forename: Raymond
authors.initials: R
authors.lastname: Ziessel
keywords: dyes/pigments; energy transfer; photobleaching; photochemistry; solar energy conversion