PARENT SESSION
Posters P4Aa Chlorophyll and bilin based antenna systems. Abstracts (239-271)

Long-range excitation transfer in bonded porphyrin structures. Robert Forties^*,1, Eve Hindin², Robert Loewe³, Arounaguiry Ambroise³, Christine Kirmaier², David Bocian⁴, Jonathan Lindsey³, Dewey Holten², Robert Knox^*,1, ¹ University of Rochester, Rochester, NY, USA² Washington University, St Louis, MO, USA³ North Carolina State University, Raleigh, NC, USA⁴ University of California, Riverside, CA, USA

ABSTRACT- Although Forster theory appears adequate to explain most photosynthetic antenna singlet-singlet transfer dynamics, this is not the case in certain other porphyrin structures proposed as components of efficient light harvesting systems [1]. What differentiates these structures from most antennas is direct bonding of the porphyrins through bridges [1,2]. In some structures pairwise excitation transfer rates are enhanced by factors of 10-100 over the Forster-predicted rate, an effect attributed to "through-bond transfer" [3]. We have analyzed the measured excitation transfer times in a series of bonded zinc porphyrin structures [4] and find that, in addition, significant rates of transfer between non-neighboring porphyrins (again higher than Forster's) must exist to explain the data. Here we report on the computational procedures used to deduce a consistent set of empirical inter-porphyrin rate constants in the series of structures. The method reveals the normally inaccessible putative rates of transfer between identical chromophores. 1. D. Holten, D. F. Bocian, and J. S. Lindsey, Acc. Chem. Res. 35, 57-69 (2002) 2. D. Kim and A. Osuka, J. Phys. Chem. A 107, 8791-8816 (2003) 3. S. Speiser, Chem. Revs. 96, 1953-1976 (1996) 4. E. Hindin, R. A. Forties, R. S. Loewe, A. Ambroise, C. Kirmaier, D. F. Bocian, J. S. Lindsey, D. Holten, and R. S. Knox, subm. to J. Phys. Chem.

KEY WORDS: antenna, excitation transfer, porphyrins, through-bond transfer