CHROMOPHORE-LABELED DENDRONS AS LIGHT-HARVESTING ANTENNAE

A novel series of polyether dendrimer segments (dendrons) end-clipped with pyrenyl, naphthyl, or methyl groups has been prepared by a conver gent growth method. Steady-state fluorescence measurements indicate th e absence of intramolecular naphthalene excimer in the naphthyl-capped dendrons. However, in the pyrenyl-capped dendrons, excimer emission p redominates. Fluorescence from both the naphthyl monomer and pyrenyl e xcimer are quenched when a suitable electron donor (e.g., a 3-[dimethy lamino]phenoxy group) is covalently attached at the dendron focal poin t. No sensitized emission from the dendron backbone is observed in the chromophore-labeled dendrons, although the control methyl-capped dend ron fluoresces weakly at 310 nn when excited at 284 nm. Absorption and fluorescence spectra, fluorescence quantum yields, and fluorescence l ifetimes for the chromophore-labeled dendrons are reported.