Fullerene-bound dendrimers: soluble, isolated carbon clusters

Abstract

The coupling of compact dendritic macromolecules with prefunctionalized fullerenes is now described. This synthetic strategy, involving two species containing a precise number of functional groups, gives greater control over the formation of polymer-fullerene hybrid structures. Phenol-functionalized fullerenes have been prepared by reaction of C[sub 60] with bis(p-methoxyphenyl)diazomethane followed by hydrolysis of the methyl ethers with BBr[sub 3]. This synthesis has been tailored to yield a 6-6 bridged methano fullerene derivative carrying only two phenolic sites as the major product. Polyether dendrimers prepared by the convergent synthesis route are ideally suited for attachment to phenol-functionalized buckyballs since they carry a single electrophilic site at their focal point, and their attachment to phenolic moieties has been studied extensively. The formation of fullerene-bound dendrimers was accomplished by reaction of each of the two phenolic groups located at the surface of the functionalized fullerene with the single benzylic bromide group at the focal point of a fourth-generation dendrimer in the presence of K[sub 2]CO[sub 3]. Purification by flash chromatography or precipitation gave only partial separation of the products; as a result, preparative SEC was used to obtain samples of each of the products. A [sup 1]H NMR spectrum of the desired product, in whichmore » two dendrimers are attached to the surface of the fullerene, is shown. 9 refs., 2 figs.« less