Molecular Dynamics of Poly(benzylphenyl ether) Dendrimers:  Effects of Backfolding on Förster Energy-Transfer Rates

We present the results of structural studies of poly(benzylphenyl ether) dendrimers (PBPE dendrimers) using classical molecular dynamics simulations. Specifically, we focus on four generations of PBPE dendrimer at 298 K. Our objectives are to calculate donor/acceptor distances and Förster energy-transfer rates as a function of dendrimer generation. Analyses of the trajectories from molecular dynamics simulations provide information about the radius of gyration and atomic and phenyl group density distributions in generations one through four of the dendrimer. Several different methods for computing rate constants are discussed. The methods include various estimates of average donor/acceptor distances and direct exponential fits to simulated rise-time data. The results can be correlated with observed photophysical properties of dendrimers in related systems containing donor/acceptor pairs. We demonstrate that the wrapping of peripheral groups to the core of the dendrimer leads to very short donor/acceptor distances that dominate the energy-transfer rates.