Ultrafast excited-state dynamics of phenyleneethynylene oligomers in solution.
The excited-state dynamics of oligomeric phenyleneethynylenes (OPEs) of various length and substitution has been investigated by femtosecond time-resolved spectroscopy. The fluorescence lifetime of the OPEs decreases with the number of phenyleneethynylene units up to about 9. This effect is due to an increase of the oscillator strength for the S(1)-S(0) transition. Dynamic features occurring within a few tens of picoseconds and ascribed to structural relaxation directly after population of the S(1) state can be observed in non-viscous solvents. The effect of torsional disorder on the fluorescence intensity is shown to depend strongly on the nature of the substituent on the phenyl groups. All these effects are qualitatively discussed with a simple exciton model.
Duvanel
Guillaume
G
Department of Physical Chemistry of the University of Geneva, 30 quai Ernest-Ansermet, CH-1211, Geneva 4, Switzerland.
Grilj
Jakob
J
Schuwey
Anne
A
Gossauer
Albert
A
Vauthey
Eric
E