Multi-scale Computational Analysis of Photophysical Properties of Polypyridylruthenium Derivatized Polystyrenes
Shahar Keinan, Zoe Watson, and Yosuke Kanai
Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Vendredi 5 Juillet 2013, 11h00
bibliothèque LCT, tour 12 - 13, 4e étage
Ruthenium-containing metallopolymers with a polystyrene backbone can be used for energy transfer materials. A multi-level computational approach for investigating such polymers, especially studying how the polymers geometry is changed by varying linker lengths as well as how polymer dynamics influences optoelectronic properties of the covalently attached Ru-bpy complexes, is reported here. The approach makes use of first-principles, semi-empirical electronic structure calculations as well as molecular dynamics simulations in order to systematically address the challenge associated with the stochastic nature of the polymer dynamics. The efficiency of energy transfer along the polymer is influenced by the distance between nearest-neighbor Ru atoms. Molecular dynamics simulations of polymers with various spatial arrangements of the pendant Ru complex chromophores suggest that the carbonyl-amino-methylene linker provides shorter Ru-Ru nearest-neighbor distances, which leads to an increased Ru*-Ru energy hopping rate, compared to those with longer linker counterpart polymers. The electronic structure of individual polypyridyl-ruthenium pendant obtained from molecular dynamics runs were also analyzed using semi-empirical electronic structure calculations. These calculations are used to examine the HOMO and LUMO energies as well as the optical energy gap for each monomer unit of the polymers to gain insight into the importance of dynamics on the mechanism and dynamics of exciton and charge transport within these polymer assemblies, especially studying the long-lived metal to ligand charge transfer (MLCT) excited states.