Chemical modification of C-60 for materials science applications

Fullerene derivatives have shown a wide range of physical and chemical properties that make them attractive for the preparation of supramolecular assemblies and new materials. As a part of this research, we are interested in the chemical modi. cation of C-60 for various applications. These results are summarized in the present account to illustrate the current state-of-the-art of fullerene chemistry for the development of new advanced materials. In the first part, some of the fundamental architectural requirements needed for the design of amphiphilic fullerene derivatives capable of forming stable Langmuir films are reported. In particular, we have shown that the encapsulation of C-60 in a cyclic addend surrounded by long alkyl chains, cholesterol subunits or dendritic branches is an efficient strategy to prevent the irreversible aggregation resulting from the strong fullerene-fullerene interactions usually observed for amphiphilic C-60 derivatives at the air-water interface. In the second part, water-soluble C-60 derivatives and fullerene-functionalized dendrimers are described. These compounds are easy to process, owing to their high solubility, and thus easily incorporated in mesoporous silica glasses for optical limiting applications. Finally, our recent developments on organic photovoltaic cells using covalently linked fullerene-(pi-conjugated oligomer) ensembles as the active layer are summarized. This molecular approach appears to be particularly interesting since the behavior of a unique molecule in a photovoltaic cell and the study of its electronic properties means one can easily obtain the structure-activity relationships leading to a better understanding of the photovoltaic conversion.