DENDRIMERS PERIPHERALLY MODIFIED WITH A ANION-RADICALS THAT FORM PI-DIMERS AND PI-STACKS

Poly(amidoamine) (PAMAM) dendrimers, generations 1-6, were peripherall y modified with cationically substituted naphthalene diimide groups. S everal monomeric diimides were also prepared as models. The structure and loading of the dendrimers were determined by vis, IR, and NMR spec troscopies, elemental analysis, and coulometric analysis. In general i t was possible to obtain loadings greater than 70% even from generatio n 6 dendrimer where there are 192 amine groups to be substituted. Thes e polymers and monomers were reduced using sodium dithionite or electr ochemically with one electron per imide group converting each imide in to its anion radical. Near-infrared(NIR) spectroscopy showed that in D 2O or formamide solutions the anion radicals aggregated into pi-dimers and pi-stacks. Cyclic voltammograms are interpreted in terms of anion radical aggregation and precipitation of the reduced dendrimers. The CV and NIR results for the various dendrimer generations were quite si milar. These results allow insight into the possibilities and limitati ons of dendrimers to provide a scaffold for intramolecular aggregation .