Structural Control of Photoinduced Energy Transfer between Adjacent and Distant Sites in Multiporphyrin Arrays
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- 作者：Robin K. Lammi ; Arounaguiry Ambroise ; Thiagarajan Balasubramanian ; Richard W. Wagner ; David F. Bocian ; Dewey Holten ; and Jonathan S. Lindsey
- 刊名：Journal of the American Chemical Society
- 出版年：2000
- 出版时间：August 9, 2000
- 年：2000
- 卷：122
- 期：31
- 页码：7579 - 7591
- 全文大小：411K
- 年卷期：v.122,no.31(August 9, 2000)
- ISSN：1520-5126
文摘
A family of diphenylethyne-linked porphyrin dimers and trimers has been prepared via a buildingblock approach for studies of energy-transfer processes. The dimers contain Mg and Zn porphyrins (MgZnU);the trimers contain an additional free base porphyrin (MgZnFbU). In both the dimers and trimers, sites ofattachment to the Mg porphyrin (at the meso- or 
-position) and diphenylethyne linker (at the para- or meta-positions) were varied, producing four Mg porphyrin-Zn porphyrin arrangements with the following linkerconfigurations: meso-p/p-meso, meso-m/p-meso, -p/p-meso, and -m/p-meso. All four trimers employ ameso-p/p-meso Zn porphyrin-Fb porphyrin connection. The ground- and excited-state properties of theporphyrin dimers and trimers have been examined using static and time-resolved optical techniques. The rateof energy transfer from the photoexcited Zn porphyrin to the Mg porphyrin decreases according to the followingtrend: meso-p/p-meso (9 ps)-1 > -p/p-meso (14 ps)-1 > meso-m/p-meso (19 ps)-1 > -m/p-meso (27 ps)-1.In each compound, energy transfer between adjacent porphyrins occurs through a linker-mediated through-bond process. The rate of energy transfer between Zn and Fb porphyrins is constant in each trimer ((24 ps)-1).Energy transfer from the photoexcited Zn porphyrin branches to the adjacent Fb and Mg porphyrins, withnearly one-half to three-fourths proceeding to the Mg porphyrin (depending on the linker). Energy transferfrom the excited Mg porphyrin to the nonadjacent Fb porphyrin occurs more slowly, with a rate that followsthe same trend in linker architecture and porphyrin connection site: meso-p/p-meso (173 ps)-1 > -p/p-meso(225 ps)-1 > meso-m/p-meso (320 ps)-1 > -m/p-meso (385 ps)-1. The rate of transfer between nonadjacentMg and Fb porphyrins does not change significantly with temperature, indicating a superexchange mechanismutilizing orbitals/states on the intervening Zn porphyrin. Energy transfer between nonadjacent sites may proveuseful in directing energy flow in multiporphyrin arrays and related molecular photonic devices.
-position) and diphenylethyne linker (at the para- or meta-positions) were varied, producing four Mg porphyrin-Zn porphyrin arrangements with the following linkerconfigurations: meso-p/p-meso, meso-m/p-meso, -p/p-meso, and -m/p-meso. All four trimers employ ameso-p/p-meso Zn porphyrin-Fb porphyrin connection. The ground- and excited-state properties of theporphyrin dimers and trimers have been examined using static and time-resolved optical techniques. The rateof energy transfer from the photoexcited Zn porphyrin to the Mg porphyrin decreases according to the followingtrend: meso-p/p-meso (9 ps)-1 > -p/p-meso (14 ps)-1 > meso-m/p-meso (19 ps)-1 > -m/p-meso (27 ps)-1.In each compound, energy transfer between adjacent porphyrins occurs through a linker-mediated through-bond process. The rate of energy transfer between Zn and Fb porphyrins is constant in each trimer ((24 ps)-1).Energy transfer from the photoexcited Zn porphyrin branches to the adjacent Fb and Mg porphyrins, withnearly one-half to three-fourths proceeding to the Mg porphyrin (depending on the linker). Energy transferfrom the excited Mg porphyrin to the nonadjacent Fb porphyrin occurs more slowly, with a rate that followsthe same trend in linker architecture and porphyrin connection site: meso-p/p-meso (173 ps)-1 > -p/p-meso(225 ps)-1 > meso-m/p-meso (320 ps)-1 > -m/p-meso (385 ps)-1. The rate of transfer between nonadjacentMg and Fb porphyrins does not change significantly with temperature, indicating a superexchange mechanismutilizing orbitals/states on the intervening Zn porphyrin. Energy transfer between nonadjacent sites may proveuseful in directing energy flow in multiporphyrin arrays and related molecular photonic devices.