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 ‐(G n ) 2 Ar], having generation numbers ( n ) of 0–3, were synthesized. 1 H NMR pulse relaxation times ( T 1 ) of the exterior MeO groups of o ‐ and m ‐(G n ) 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 ‐(G n ) 2 Ar increased, but that of p ‐(G n ) 2 Ar decreased, whereas m ‐(G n ) 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.