Stuttgart 2012 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 9: Femtosecond Spectroscopy II
MO 9.4: Vortrag
Dienstag, 13. März 2012, 11:30–11:45, V38.03
Ultrafast emission quenching in a perylene diimide by structure rearrangement induced electron transfer from its substituent — •Patrick Kölle1, Artur Nenov1, Uwe Megerle2, Patrizia Krok2, Heinz Langhals1, Regina de Vivie-Riedle1, and Eberhard Riedle2 — 1Ludwig-Maximilians-Universität München, Department Chemie, Germany — 2Ludwig-Maximilians-Universität München, Lehrstuhl für BioMolekulare Optik, Germany
The ultrafast excited-state dynamics of the fluorescent perylene diimide chromophore and its non-fluorescent amino-functionalized derivative are investigated by transient spectroscopy and quantum chemical calculations. The fluorescent system shows no dynamics in the sub-nanosecond time region. For the functionalized molecule the stimulated emission signal decays rapidly on a sub-picosecond timescale, while the excited state absorption decreases with a time constant of several picoseconds. The theoretical analysis assigns the fast decay to a charge transfer from the amino substitutient to the perylene diimide chromophore. The transfer is made possible by a decrease of the N-N distance and a planarization of the substituent as the system moves away from the Franck-Condon point. Experiments in different solvents demonstrate that the dynamics of this fluorescence quenching correlate with the solvation time. The rapid relaxation from the charge transfer state into the ground state is observed on a picosecond timescale and is attributed to a passage through a conical intersection.