bis-Dendron poly(aryl ether) dendrimers Py-[Gn]2-NPh (n＝1～2) with only one pyrene chromophore at the periphery and an anilino group at the core were synthesized and the extent of folding back conformation was given by the intramolecular electron transfer and exciplex formation. Selective excitation of the periphery pyrene moiety of Py-[Gn]2-NPh in dichloromethane results in an electron transfer process from aniline moiety to pyrene group, and as a consequence of the electron transfer an intramolecular exciplex is formed. Since the exciplex formation requires a direct orbital overlap between the donor and the acceptor groups, this gives us a directly experimental observation for the folding back conformation of bis-dendron poly(aryl ether) dendrimers. The efficiencies and the rate constants of electron transfer in dichloromethane are 0.87, 0.81 and 2.3×108, 1.5×108 s－1 for generations 1～2, respectively. The distances between the donor and acceptor (center to center) were estimated from the rate constants of electron transfer to be, 0.79 and 0.81 nm for genertions 1～2, respectively. This means that the periphery chromophores can fold inward and reach the core vicinity for Py-[Gn]2-NPh, which is similar to the mono-dendron dendrimers Py-Gn-NHPh.

Key words: poly(aryl ether) dendrimer, conformation, intramolecular electron transfer, exciplex