Ultrafast Energy Relaxation and Excitation Delocalization in Excited States of Zinc Porphyrin Dimers and Trimer

I. Yamazaki, S. Akimoto, T. Yamazaki Graduate School of Molecular Chemistry, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan H. Shiratori and A. Osuka Graduate School of Chemistry, Kyoto University, Sakyo-ku, Kyoto 606-8224, Japan

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Ultrafast excited-state relaxation process has been studied with zinc porphyrin dimers and circular trimer. Following 80 fs excitation at Soret band (420 nm) or Q band (580 nm) of zinc porphyrin, the fluorescence decay curves exhibit ultrafast decays with lifetimes of 80 fs in o-dimer, 450 fs in trimer and 540 fs in m-dimer. The timeresolved fluorescence spectra show that the fast decay process correspond to disappearance of monomer-like emission followed by red-shifted and broaden spectra. These ultrafast processes are assigned as due to excitation transfer among monomers and delocalization of excitation yielding excitonic states.

DOI: 10.12693/APhysPolA.95.105 PACS numbers: 31.50.+w, 78.47.+p