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Chemistry
Revealing competitive Förster-type resonance energy-transfer pathways in single bichromophoric molecules
*Laboratory for Photochemistry and Spectroscopy, Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium; Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany; ¶Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany; ||Chemistry of Novel Materials, University of Mons-Hainaut, Place du Parc, 20, B-7000 Mons, Belgium; and **Department of Chemistry, University of Arizona, Tucson, AZ 85721-0041
Communicated by Michael Kasha, Florida State University, Tallahassee, FL, September 10, 2003 (received for review February 21, 2003)
We demonstrate measurements of the efficiency of competing Förster-type energy-transfer pathways in single bichromophoric systems by monitoring simultaneously the fluorescence intensity, fluorescence lifetime, and the number of independent emitters with time. Peryleneimide end-capped fluorene trimers, hexamers, and polymers with interchromophore distances of 3.4, 5.9, and on average 42 nm, respectively, served as bichromophoric systems. Because of different energy-transfer efficiencies, variations in the interchromophore distance enable the switching between homo-energy transfer (energy hopping), singlet-singlet annihilation, and singlet-triplet annihilation. The data suggest that similar energy-transfer pathways have to be considered in the analysis of single-molecule trajectories of donor/acceptor pairs as well as in natural and synthetic multichromophoric systems such as light-harvesting antennas, oligomeric fluorescent proteins, and dendrimers. Here we report selectively visualization of different energy-transfer pathways taking place between identical fluorophores in individual bichromophoric molecules.
Present address: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306.
To whom correspondence may be addressed. E-mail: johan.hofkens{at}chem.kuleuven.ac.be or frans.deschryver{at}chem.kuleuven.ac.be.
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