Osnabrück 2002 – wissenschaftliches Programm

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MO: Molekülphysik

MO 8: Energietransfer, Reaktionen

MO 8.1: Vortrag

Mittwoch, 6. März 2002, 14:00–14:15, HS 01/E01

Excitonic Interactions in Mesoscopic Molecular Assemblies — •Joerg Zimmermann, Xanthipe J. Jordanides, and Graham R. Fleming — University of California, Berkeley, Department of Chemistry

Excitonic coupling between dye molecules is the key mechanism for distribution and vectorial transfer of excitation energy in supramolecular assemblies, thus employed in molecular electronics as well as in photosynthetic light harvesting. It can be described using different levels of complexity, reaching from the simple point-dipole approximation (PDA) to sophisticated ab-initio methods. However, when it comes to mesoscopic systems, costly methods are not suitable due to the large size of the system. Recently, a new method called TDC was developed and applied to the reaction center of photosynthetic bacteria [1,2]. TDC is a promising approach to larger systems because the No-dqresolutionNo-dq of the method is adjustable. This is demonstrated for aggregates of free-base porphyrins varying the number of molecules within the aggregate. The TDC results are compared to PDA and distributed-monopole-approximation calculations. All three methods are then applied to model the absorption spectrum of a mesoscopic porphyrin aggregate [3] showing the failure of the more simple approaches. [1] B.P. Krueger, G.D. Scholes, G.R. Fleming, J. Phys. Chem. B 1998, 102, 5378 [2] G.D. Scholes, X.J. Jordanides, G.R. Fleming, J. Phys. Chem. B 2001, 105, 1640 [3] C. Endisch, C. Böttcher, J.-H. Fuhrhop, J. Am. Chem. Soc. 1995, 117, 8273