Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 86: Plasmonics and Nanooptics VI
O 86.3: Vortrag
Freitag, 15. März 2013, 11:00–11:15, H36
Dynamic exciton self-trapping in extended pi-electron systems revealed in single giant macrocycles. — Vikas Aggarwal1, Alex Thiessen2, Alisa Idelson1, •Dominik Würsch3, Thomas Stangl3, Florian Steiner3, Stefan-S. Jester1, Jan Vogelsang3, Sigurd Höger1, and John Lupton3 — 1University of Bonn, Bonn, Germany — 2University of Utah, Salt Lake City, Utah, USA — 3University of Regensburg, Regensburg, Germany
Natural light-harvesting complexes have long served as model systems of the physics of molecular excitons. Synthetic model systems which mimic specific aspects of exciton coupling would allow investigating the effects of coupling in a highly defined system. Here we introduce giant shape persistent macrocycles of carbazole-enthynylene units of 7 nm diameter. Fully conjugated macrocycles are generally considered to be non-emissive because the fundamental oscillator mode is dipole forbidden. For every electron which moves in one direction there is another moving in exactly the opposite direction, resulting in a vanishing dipole moment. Spontaneous fluctuations in the conjugation lead to strongly allowed fluorescence of the system which enables single molecule studies of the emitter. We find that the conjugation varies with time resulting in jumps in the linear dichroism. The conjugation of the macrocycle is dynamically interrupted leading to more than one chromophore being present. Surprisingly, we find that the emission polarization can rotate without a change in transition energy, implying that the different chromophores on the ring remain susceptible to the same dielectric environment.