Investigations of Light Harvesting and Enhanced Nonlinear Optical Properties in Organic Dendrimers and Branched Macromolecules – Theodore Goodson III

Date: Mon. March 28th, 2005, 12:30 pm-1:30 pm
Location: Rockefeller 221

Organic conjugated macromolecules have received great attention due to their use in optical and electronic applications. Certain molecular aggregate systems have shown enhanced nonlinear optical properties by virtue of excitonic coupling in the multi-chromophore system. Organic dendrimers and other branched multi-chromophore systems (where the chromophores are covalently attached) have also shown characteristic properties of strong intramolecular interactions which have been utilized in light harvesting processes, light emitting diodes, as well as for enhanced nonlinear optical effects. The mechanism of the strong intramolecular interactions in branched chromophores depends on the nature of the branching center, the geometrical orientation of covalently attached chromophores, and the extent of delocalization in the dendrons. Through steady-state and time-resolved spectroscopy, we have characterized the mechanism of energy transport and the relative strength of intra-molecular interactions. In this presentation, organic dendrimers and other branched chromophores are described by their time-resolved fluorescence and absorption properties. Different dendrimers with varying branching centers, dendrons, and degree of intramolecular interactions will be presented. For particular dendrimer systems the processes of efficient energy transfer, fast energy redistribution, enhanced two-photon absorption cross-sections, and a delocalized excitation with weaker electronic copuling to the bath (solvent) will be discussed.