title: Electron, Hole, Singlet, and Triplet Energy Transfer in Photoexcited Porphyrin-Naphthalenediimide Dyads.
abstract: The excited-state dynamics of two molecular dyads, consisting of zinc (1) and free-base (2) porphyrin connected via a peptide linker to a core-substituted naphthalenediimide (NDI) have been investigated using optical spectroscopy. These dyads exhibit rich photophysics because of the large number of electronic excited states below 3 eV. In the case of 1 in apolar solvents, excitation energy transfer from the vibrationally hot singlet excited porphyrin to the NDI takes place with a 500 fs time constant. Electronic energy ends up in the NDI-localized triplet state, which decays to the ground state on a microsecond timescale. In polar solvents, ground-state recovery is faster by 5 orders of magnitude because of the occurrence of charge separation followed by recombination. On the other hand, excitation energy transfer in 2 takes place in the opposite direction, namely from the NDI to the porphyrin, which then undergoes intersystem crossing to the triplet state, followed by triplet energy transfer back to the NDI. Therefore, four distinct local electronic excited states are consecutively populated after excitation of the NDI unit of 2, with the energy shuttling between the two ends of the dyad.
authors.affiliation: †Department of Physical Chemistry, University of Geneva, 30 quai Ernest-Ansermet, CH-1211 Geneva, 4, Switzerland.
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Yushchenko
authors.affiliation: ‡Department of Organic Chemistry, School of Chemical Sciences, North Maharashtra University, Jalgaon, 425 001 Maharashtra, India.
authors.forename: Rahul V
authors.initials: RV
authors.lastname: Hangarge
authors.affiliation: †Department of Physical Chemistry, University of Geneva, 30 quai Ernest-Ansermet, CH-1211 Geneva, 4, Switzerland.
authors.forename: Sandra
authors.initials: S
authors.lastname: Mosquera-Vazquez
authors.affiliation: §School of Applied Sciences, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia.
authors.forename: Sheshanath V
authors.initials: SV
authors.lastname: Boshale
authors.affiliation: †Department of Physical Chemistry, University of Geneva, 30 quai Ernest-Ansermet, CH-1211 Geneva, 4, Switzerland.
authors.forename: Eric
authors.initials: E
authors.lastname: Vauthey
mesh_terms: D004583:Electrons; D004735:Energy Transfer; D007094:Imides / Q000737:chemistry*; D015394:Molecular Structure; D009281:Naphthalenes / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D055668:Photochemical Processes; D016062:Porosity; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D015032:Zinc / Q000737:chemistry
chemical_list: D007094:Imides; D009281:Naphthalenes; D009942:Organometallic Compounds; D011166:Porphyrins; C542131:naphthalenediimide; D015032:Zinc