Singlet fission is a mechanism by which a singlet excited state separates into two triplet excited states on neighboring molecules. The process was observed several decades ago in light harvesting complexes of purple bacteria. Recently, we have aimed to address whether the mechanism can have a beneficial role in biology, for example in photoprotection. We have focused on model systems of the carotenoid zeaxanthin in unilamellar lipid vesicles.  Our methods include steady-state photolysis and spectroscopy, along with time-resolved optical experiments. The results indicate that singlet fission is a significant pathway when zeaxanthin is self-assembled in the gel phase of the bilayers. However, the channel is not active when the carotenoids are monomeric, in the fluid phase. These findings and others suggest that singlet fission could play a role in dissipating excess photon energy in biological systems where chromophores are coupled.

Does singlet fission serve a functional role in biological systems?

244th National Meeting (2012)

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