I. Tabakovic et al., DENDRIMERS PERIPHERALLY MODIFIED WITH A ANION-RADICALS THAT FORM PI-DIMERS AND PI-STACKS, Chemistry of materials, 9(3), 1997, pp. 736-745
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
.