Uncovering dark multichromophoric states in Peridinin-Chlorophyll-Protein.

Elliot J Taffet, Francesca Fassioli, Zi S D Toa, David Beljonne, Gregory D Scholes

Journal of the Royal Society, Interface 2020 Mar

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It has long been recognized that visible light harvesting in Peridinin-Chlorophyll-Protein is driven by the interplay between the bright (S2) and dark (S1) states of peridinin (carotenoid), along with the lowest-lying bright (Qy) and dark (Qx) states of chlorophyll-a. Here, we analyse a chromophore cluster in the crystal structure of Peridinin-Chlorophyll-Protein, in particular, a peridinin-peridinin and a peridinin-chlorophyll-a dimer, and present quantum chemical evidence for excited states that exist beyond the confines of single peridinin and chlorophyll chromophores. These dark multichromophoric states, emanating from the intermolecular packing native to Peridinin-Chlorophyll-Protein, include a correlated triplet pair comprising neighbouring peridinin excitations and a charge-transfer interaction between peridinin and the adjacent chlorophyll-a. We surmise that such dark multichromophoric states may explain two spectral mysteries in light-harvesting pigments: the sub-200-fs singlet fission observed in carotenoid aggregates, and the sub-200-fs chlorophyll-a hole generation in Peridinin-Chlorophyll-Protein.

Citation

Elliot J Taffet, Francesca Fassioli, Zi S D Toa, David Beljonne, Gregory D Scholes. Uncovering dark multichromophoric states in Peridinin-Chlorophyll-Protein. Journal of the Royal Society, Interface. 2020 Mar;17(164):20190736