Photophysical study of a multi-chromophoric dendrimer by time-resolved fluorescence and femtosecond transient absorption spectroscopy

The photophysical properties of a dendrimer (1) bearing eight peryleneimide chromophores on a polyphenylene care were investigated by picosecond fluor escence and femtosecond transient absorption techniques. A peryleneimide at tached to a hexaphenylbenzene unit (2) served as model compound. Multi-expo nential fluorescence and fs-transient absorption decays were observed only for 1, which could therefore be attributed to excimer-like interactions amo ng neighbouring peryleneimides. The comparative time-resolved polarisation results on 1 and 2 indicate the occurrence of different depolarisation proc esses in the dendrimer assignable to the rotation of the molecule, a fracti onal motion maybe of a dendrimer branch and to an intramolecular energy tra nsfer process. (C) 1999 Elsevier Science B.V. All rights reserved.