title: Biphasic self-assembly pathways and size-dependent photophysical properties of perylene bisimide dye aggregates.
abstract: The concentration-dependent absorption and temperature-dependent fluorescence of the perylene bisimide dye PBI 1 in methylcyclohexane point to a biphasic aggregation behavior. At intermediate concentrations and temperatures, respectively, a dimer with low fluorescence yield dominates, which cannot be extended to longer aggregates. Those are formed at high concentrations and low temperatures, respectively, via a second, energetically unfavorable dimer species that acts as a nucleus. A corresponding aggregation model reproduces accurately the concentration dependence and allows extracting the equilibrium constants and spectra of the distinct species. The differences in the photophysical properties indicate H-type excitonic coupling for the favored dimer and J-type characteristics for the extended aggregates which could be related to structural models based on DFT calculations. The energetics can be understood by considering hydrogen-bonding and π-π-stacking interactions.
authors: Institut für Physik, Universität Rostock , D-18051 Rostock, Germany.
authors: Franziska
authors: F
authors: Fennel
authors: Steffen
authors: S
authors: Wolter
authors: Zengqi
authors: Z
authors: Xie
authors: Per-Arno
authors: PA
authors: Plötz
authors: Oliver
authors: O
authors: Kühn
authors: Frank
authors: F
authors: Würthner
authors: Stefan
authors: S
authors: Lochbrunner