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Control of electron transfer in supramolecular systems
K Kilså1, A N Macpherson, T Gillbro
1Department of Physical Chemistry, Chalmers University of Technology, Göteborg, Sweden.
Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
|October 18, 2001
Summary
Solvent properties control fluorescence in zinc porphyrin-anthracene systems. Adding Lewis bases quenches fluorescence via electron transfer, a process tunable by solvent effects.
Area of Science:
- Photochemistry
- Supramolecular Chemistry
- Materials Science
Background:
- Zinc porphyrin (ZnP) and 9,10-bis(phenylethynyl)anthracene (AB) are key chromophores.
- Understanding photoinduced electron transfer is crucial for molecular electronics and energy conversion.
Purpose of the Study:
- To investigate the solvent-dependent fluorescence quantum yield of a ZnP-AB bichromophoric system.
- To elucidate the mechanism of fluorescence quenching in the presence of Lewis bases.
- To explore the potential for tuning electron transfer processes through solvent effects.
Main Methods:
- Picosecond transient absorption spectroscopy
- Fluorescence quenching measurements
- Cyclic voltammetry
Main Results:
- ZnP-AB fluorescence is solvent-dependent, exhibiting normal emission in non-coordinating solvents.
- Lewis bases, like pyridine, in polar solvents significantly quench ZnP fluorescence.
- Intramolecular electron transfer from ZnP to AB, forming ZnP*+-AB*-, occurs with a lifetime < 220 ps.
- A ternary system (ZnP-AB-FeP) shows enhanced charge separation with a lifetime > 5 ns, demonstrating tunable electron transfer.
Conclusions:
- Solvent polarity and Lewis base coordination critically influence the photophysical properties of ZnP-AB.
- Intramolecular electron transfer is the primary quenching mechanism, controllable by external factors.
- The study highlights the potential for designing systems with switchable electron transfer functionalities.