title: The nature of the intramolecular charge transfer state in peridinin.
abstract: Experimental and theoretical evidence is presented that supports the theory that the intramolecular charge transfer (ICT) state of peridinin is an evolved state formed via excited-state bond-order reversal and solvent reorganization in polar media. The ICT state evolves in <100 fs and is characterized by a large dipole moment (~35 D). The charge transfer character involves a shift of electron density within the polyene chain, and it does not involve participation of molecular orbitals localized in either of the β-rings. Charge is moved from the allenic side of the polyene into the furanic ring region and is accompanied by bond-order reversal in the central portion of the polyene chain. The electronic properties of the ICT state are generated via mixing of the "1(1)Bu(+)" ionic state and the lowest-lying "2(1)Ag(-)" covalent state. The resulting ICT state is primarily (1)Bu(+)-like in character and exhibits not only a large oscillator strength but an unusually large doubly excited character. In most solvents, two populations exist in equilibrium, one with a lowest-lying ICT ionic state and a second with a lowest-lying "2(1)Ag(-)" covalent state. The two populations are separated by a small barrier associated with solvent relaxation and cavity formation.
authors.affiliation: Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA.
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Wagner
authors.forename: Jordan A
authors.initials: JA
authors.lastname: Greco
authors.forename: Miriam M
authors.initials: MM
authors.lastname: Enriquez
authors.forename: Harry A
authors.initials: HA
authors.lastname: Frank
authors.forename: Robert R
authors.initials: RR
authors.lastname: Birge
mesh_terms: D002338:Carotenoids / Q000737:chemistry*; D004579:Electron Transport; D004583:Electrons; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D012997:Solvents / Q000737:chemistry
chemical_list: D012997:Solvents; C016040:peridinin; D002338:Carotenoids