title: Torsional Dynamics and Intramolecular Charge Transfer in the S2 (1(1)Bu(+)) Excited State of Peridinin: A Mechanism for Enhanced Mid-Visible Light Harvesting.
abstract: Of the carotenoids known in photosynthetic organisms, peridinin exhibits one of the highest quantum efficiencies for excitation energy transfer to chlorophyll (Chl) a acceptors. The mechanism for this enhanced performance involves an order-of-magnitude slowing of the S2 (1(1)Bu(+)) → S1 (2(1)Ag(-)) nonradiative decay pathway compared to carotenoids lacking carbonyl substitution. Using femtosecond transient grating spectroscopy with optical heterodyne detection, we have obtained the first evidence that the nonradiative decay of the S2 state of peridinin is promoted by large-amplitude torsional motions. The decay of an intermediate state termed Sx, which we assign to a twisted form of the S2 state, is substantially slowed by solvent friction in peridinin due to its intramolecular charge transfer (ICT) character.
authors: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1322, United States.
authors: Soumen
authors: S
authors: Ghosh
authors: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1322, United States.
authors: Jerome D
authors: JD
authors: Roscioli
authors: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1322, United States.
authors: Michael M
authors: MM
authors: Bishop
authors: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1322, United States.
authors: Jason K
authors: JK
authors: Gurchiek
authors: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269-3036, United States.
authors: Amy M
authors: AM
authors: LaFountain
authors: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269-3036, United States.
authors: Harry A
authors: HA
authors: Frank
authors: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1322, United States.
authors: Warren F
authors: WF
authors: Beck