Optical switching and antenna effect of dendrimers with an anthracene core

Dendrimers 6G(i) (i=1-4) consisting of an anthracene core and Frechet dendrons which are attached via a CH2OCH2 chain in the 9-position undergo quantitative and completely reversible intramolecular [4 pi+4 pi] cycloaddition. The process can be monitored by absorption and fluorescence measurements. The Frechet dendrons act as an energy funnel that collects and focuses the photon energy but does not change the photostationary states, which for both directions are completely on the product side when the separate chromophores are selectively irradiated. The quantum yields of anthracene fluorescence and of singlet energy transfer from the dendrons to the core were studied as a function of dendrimer generation.