Morphology-dependent luminescence properties of poly(benzyl ether) dendrimers

Poly(benzyl ether) dendrimers with o-, m-, and p-isomers of dialkoxybenzene at their focal points [o-, m-, and p-(Gn)(2)Ar], having generation numbers (n) of 0-3, were synthesized. H-1 NMR pulse relaxation times (T-1) of the exterior MeO groups of o-and m-(Gn)(2)Ar (n = 0-3) all remained in the range of 0.92-1.43 s. In sharp contrast, an exceptionally short T-1 value (0.23 s) was observed for p-(G3)(2)Ar. Although their absorption spectral profiles were slightly different from one another, an essential difference was observed for their fluorescence properties. When the generation number was increased, the fluorescence efficiency of o-(Gn)(2)Ar increased, but that of p-(Gn)(2)Ar decreased, whereas m-(Gn)(2)Ar exhibited a relatively small change in the fluorescence efficiency. Fluorescence depolarization studies showed a highly efficient intramolecular energy migration in p-(G3)(2)Ar as compared with o-(G3)(2)Ar and m-(G3)(2)Ar. (C) 2003 Wiley Periodicals, Inc.