title: Dynamics of Energy Transfer in a Conjugated Dendrimer Driven by Ultrafast Localization of Excitations.
abstract: Solar energy conversion starts with the harvest of light, and its efficacy depends on the spatial transfer of the light energy to where it can be transduced into other forms of energy. Harnessing solar power as a clean energy source requires the continuous development of new synthetic materials that can harvest photon energy and transport it without significant losses. With chemically-controlled branched architectures, dendrimers are ideally suited for these initial steps, since they consist of arrays of chromophores with relative positioning and orientations to create energy gradients and to spatially focus excitation energies. The spatial localization of the energy delimits its efficacy and has been a point of intense research for synthetic light harvesters. We present the results of a combined theoretical experimental study elucidating ultrafast, unidirectional, electronic energy transfer on a complex molecule designed to spatially focus the initial excitation onto an energy sink. The study explores the complex interplay between atomic motions, excited-state populations, and localization/delocalization of excitations. Our findings show that the electronic energy-transfer mechanism involves the ultrafast collapse of the photoexcited wave function due to nonadiabatic electronic transitions. The localization of the wave function is driven by the efficient coupling to high-frequency vibrational modes leading to ultrafast excited-state dynamics and unidirectional efficient energy funneling. This work provides a long-awaited consistent experiment-theoretical description of excited-state dynamics in organic conjugated dendrimers with atomistic resolution, a phenomenon expected to universally appear in a variety of synthetic conjugated materials.
authors.affiliation: Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States.
authors.forename: Johan F
authors.initials: JF
authors.lastname: Galindo
authors.affiliation: Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States.
authors.forename: Evrim
authors.initials: E
authors.lastname: Atas
authors.forename: Aysun
authors.initials: A
authors.lastname: Altan
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Kuroda
authors.affiliation: Universidad Nacional de Quilmes , Roque Saenz Peña 352, B1876BXD Bernal, Argentina.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Fernandez-Alberti
authors.affiliation: Theoretical Division, Center for Nonlinear Studies (CNLS) and Center for integrated Nanotechnologies (CINT), Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Sergei
authors.initials: S
authors.lastname: Tretiak
authors.affiliation: Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States.
authors.forename: Adrian E
authors.initials: AE
authors.lastname: Roitberg
authors.affiliation: Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States.
authors.forename: Valeria D
authors.initials: VD
authors.lastname: Kleiman
mesh_terms: D050091:Dendrimers / Q000737:chemistry*; D004735:Energy Transfer
chemical_list: D050091:Dendrimers