title: Analysis of state-specific vibrations coupled to the unidirectional energy transfer in conjugated dendrimers.
abstract: The nonadiabatic excited-state molecular dynamics (NA-ESMD) method and excited-state instantaneous normal modes (ES-INMs) analyses have been applied to describe the state-specific vibrations that participate in the unidirectional energy transfer between the coupled chromophores in a branched dendrimeric molecule. Our molecule is composed of two-, three-, and four-ring linear poly(phenyleneethynylene) (PPE) units linked through meta-substitutions. After an initial laser excitation, an ultrafast sequential S(3) → S(2) → S(1) electronic energy transfer from the shortest to longest segment takes place. During each S(n) → S(n-1) (n = 3, 2) transition, ES-INM(S(n)) and ES-INM(S(n-1)) analyses have been performed on S(n) and S(n-1) states, respectively. Our results reveal a unique vibrational mode localized on the S(n) state that significantly matches with the corresponding nonadiabatic coupling vector d(n,(n-1)). This mode also corresponds to the highest frequency ES-INM(S(n)) and it is seen mainly during the electronic transitions. Furthermore, its absence as a unique ES-INM(S(n-1)) reveals that state-specific vibrations play the main role in the efficiency of the unidirectional S(n) → S(n-1) electronic and vibrational energy funneling in light-harvesting dendrimers.
authors.affiliation: Universidad Nacional de Quilmes, Roque Saenz Peña 352, B1876BXD Bernal, Argentina.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Soler
authors.forename: Adrian E
authors.initials: AE
authors.lastname: Roitberg
authors.forename: Tammie
authors.initials: T
authors.lastname: Nelson
authors.forename: Sergei
authors.initials: S
authors.lastname: Tretiak
authors.forename: Sebastian
authors.initials: S
authors.lastname: Fernandez-Alberti
mesh_terms: D050091:Dendrimers / Q000737:chemistry*; D004735:Energy Transfer; D056004:Molecular Dynamics Simulation; D011108:Polymers / Q000737:chemistry*; D014732:Vibration
chemical_list: D050091:Dendrimers; D011108:Polymers; C473966:poly(phenylene ethynylene)