Ultrafast Exciton Self-Trapping upon Geometry Deformation in Perylene-Based Molecular Aggregates

Femtosecond time-resolved experiments demonstrate that the photoexcited state of perylene tetracarboxylic acid bisimide (PBI) aggregates in solution decays nonradiatively on a time-scale of 215 fs. High-level electronic structure calculations on dimers point toward the importance of an excited state intermolecular geometry distortion along a reaction coordinate that induces energy shifts and couplings between various electronic states. Time-dependent wave packet calculations incorporating a simple dissipation mechanism indicate that the fast energy quenching results from a doorway state with a charge-transfer character that is only transiently populated. The identified relaxation mechanism corresponds to a possible exciton trap in molecular materials

Thermally Polymerized Rylene Nanoparticles

Rylene dyes functionalized with varying numbers of phenyl trifluorovinyl ether (TFVE) moieties were subjected to a thermal emulsion polymerization to yield shape-persistent, water-soluble chromophore nanoparticles. Perylene and terrylene diimide derivatives containing either two or four phenyl TFVE functional groups were synthesized and subjected to thermal emulsion polymerization in tetraglyme. Dynamic light scattering measurements indicated that particles with sizes ranging from 70 to 100 nm were obtained in tetraglyme, depending on monomer concentration. The photophysical properties of individual monomers were preserved in the nanoemulsions, and emission colors could be tuned between yellow, orange, red, and deep red. The nanoparticles were found to retain their shape upon dissolution into water, and the resulting water suspensions displayed moderate to high fluorescence quantum yield.Chesonis Family Foundation. Graduate FellowshipBiophysical Instrumentation Facility for the Study of Complex Macromolecular Systems (NSF-0070319)Biophysical Instrumentation Facility for the Study of Complex Macromolecular Systems (NIH GM68762