EXCITON LOCALIZATION HIERARCHY AND DIRECTED ENERGY-TRANSFER IN CONJUGATED LINEAR AROMATIC CHAINS AND DENDRIMERIC SUPERMOLECULES

A unique class of phenylacetylene dendrimer supermolecules have been s tudied in terms of their electronic absorption and energy-transfer cha racteristics. Discrete exciton localization on isolated absorbing unit s within the dendrimer backbone is observed. Due to the branching stru cture, the vibrationless ground-state absorption is energetically pinn ed, showing complete independence of absorption energy with changes in molecular size. A simple linear-chain interacting oscillator model is used to calculate the band-edge energies of three isolated linear rin g systems: poly(p-phenylenevinylene) (PPV), polytolans, and the dendri mer series. These calculations compare favorably with the experimental data, further illustrating the tight excitation localization. (C) 199 8 Elsevier Science B.V. All rights reserved.