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Self-regulation of photoinduced electron transfer by a molecular nonlinear transducer


Organisms must adapt to survive, necessitating regulation of molecular and subcellular processes. Green plant photosynthesis responds to potentially damaging light levels by downregulating the fraction of excitation energy that drives electron transfer. Achieving adaptive, self-regulating behaviour in synthetic molecules is a critical challenge that must be met if the promises of nanotechnology are to be realized1. Here we report a molecular pentad consisting of two light-gathering antennas, a porphyrin electron donor, a fullerene electron acceptor and a photochromic control moiety. At low white-light levels, the molecule undergoes photoinduced electron transfer with a quantum yield of 82%. As the light intensity increases, photoisomerization of the photochrome leads to quenching of the porphyrin excited state, reducing the quantum yield to as low as 27%. This self-regulating molecule modifies its function according to the level of environmental light, mimicking the non-photochemical quenching mechanism2,3,4,5,6,7,8 for photoprotection found in plants.

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Figure 1: Structure of pentad 1.
Figure 2: Steady-state absorption.
Figure 3: Femtosecond transient absorption.
Figure 4: Demonstration of white-light photoprotection.
Figure 5: Nanosecond transient absorption demonstration of switching cyclability.

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This work was supported by the U.S. National Science Foundation (CHE-0352599).

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Authors and Affiliations



S.D.S. contributed to the synthesis and spectroscopic study of the molecules. G.K. performed the transient absorption experiments and interpreted them. Y.T. contributed to the synthesis. M.H. carried out electrochemical studies. All authors discussed the results and commented on the manuscript.

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Correspondence to Thomas A. Moore or Devens Gust.

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Straight, S., Kodis, G., Terazono, Y. et al. Self-regulation of photoinduced electron transfer by a molecular nonlinear transducer. Nature Nanotech 3, 280–283 (2008).

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