Insights into the mechanism of singlet fission have largely developed from experimental and theoretical studies of acene molecules. However, an alternative class of molecules, the polyenes, have important connections to singlet fission. We have previously reported singlet fission in dimers and aggregates of carotenoids that produced triplet excited states with 100 – 200% yields. To gain insights into the mechanism of this process, we have explored chromophore-chromophore coupling in dimers with a combination of temperature-dependent circular dichroism and UV-Vis absorption spectroscopy. Additionally, two resonance Raman spectra of the dimer were examined in detail: that of the isolated triplet excited state formed via sensitization of the dimer, versus correlated triplet pairs formed via singlet fission. In aggregates, time-dependent changes in certain resonance Raman bands are noted in Stokes and anti-Stokes spectra. We relate these insights into vibrational dynamics and chromophore-chromophore coupling to the mechanism of singlet fission. Focal points of this talk include the involvement of charge-transfer states, and the coupling of vibrations to the conversion of singlet – to – triplet pair states.<br/>

Singlet fission within carotenoid assemblies probed in depth with spectroscopy

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.