Conformational dynamics of di-(perylene bisimide acrylate) and its footprints in steady-state, time-resolved, and fluorescence-correlation spectroscopy.

Employing steady-state spectroscopy, time-resolved fluorescence spectroscopy, and fluorescence (cross-) correlation spectroscopy we investigated di-(perylene bisimide acrylate) and compared the results with those from monomeric perylene bisimide acrylate. For the dimeric structure two emitting species were found. By comparison with the spectroscopic results from monomeric perylene bisimide one species was assigned to perylene moieties in an isolated, unstacked conformation, whereas the other species is attributed to aggregated π-stacked perylene moieties. The transition dynamics between these conformations was uncovered by fluorescence (cross) correlation spectroscopy. A consistent description of the various correlation curves is derived for a dynamic model that considers an additional non-fluorescent dark state that is associated exclusively with the aggregated species.