Energy and Photoinduced Electron Transfer in a Wheel-Shaped Artificial Photosynthetic Antenna-Reaction Center Complex

• Published in: Journal of the American Chemical Society Vol. 128; no. 6; pp. 1818 - 1827
• Main Authors: Kodis, Gerdenis, Terazono, Yuichi, Liddell, Paul A, Andréasson, Joakim, Garg, Vikas, Hambourger, Michael, Moore, Thomas A, Moore, Ana L, Gust, Devens
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-02-2006
• Subjects: Anthracenes - chemical synthesis; Anthracenes - chemistry; Atomic and molecular physics; Biomimetic Materials - chemical synthesis; Biomimetic Materials - chemistry; Electrons; Exact sciences and technology; Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion); Kinetics; Molecular properties and interactions with photons; Photochemistry; Photosynthetic Reaction Center Complex Proteins - chemical synthesis; Photosynthetic Reaction Center Complex Proteins - chemistry; Physics; Porphyrins - chemical synthesis; Porphyrins - chemistry; Radiationless transitions, quenching; Spectrophotometry, Ultraviolet; Fluorescence spectroscopy; Fullerene compounds; Light harvesting system; Photosynthetic reaction centers; Electron transfer; Radiative lifetimes; Experimental study; Quantum yield; Non metal porphyrin; Luminescence decay; Iron Organic compounds; Biomimetic compound; Molecular complex; Energy transfer; Ultraviolet visible spectrometry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja055903c

Functional mimics of a photosynthetic antenna-reaction center complex comprising five bis(phenylethynyl)anthracene antenna moieties and a porphyrin−fullerene dyad organized by a central hexaphenylbenzene core have been prepared and studied spectroscopically. The molecules successfully integrate singlet−singlet energy transfer and photoinduced electron transfer. Energy transfer from the five antennas to the porphyrin occurs on the picosecond time scale with a quantum yield of 1.0. Comparisons with model compounds and theory suggest that the Förster mechanism plays a major role in the extremely rapid energy transfer, which occurs at rates comparable to those seen in some photosynthetic antenna systems. A through-bond, electron exchange mechanism also contributes. The porphyrin first excited singlet state donates an electron to the attached fullerene to yield a P•+−C60 •- charge-separated state, which has a lifetime of several nanoseconds. The quantum yield of charge separation based on light absorbed by the antenna chromophores is 80% for the free base molecule and 96% for the zinc analogue.