The Macromolecular, Supramolecular and Nanochemistry (MSN) program will support the collaborative research project of Prof. Alan Balch and Prof. Marilyn Olmstead of the University of California at Davis. Profs. Balch and Olmstead and their students will synthesize new fullerene derivatives that contain metal atoms in their backbone. These new fullerenes will be assembled to create unique metal organic frameworks and networks with unconventional chemical reactivity properties. These new and innovative materials are potentially transformative since they could be used as components of greatly improved catalysts and gas storage devices. The study will provide excellent training opportunities to students and postdoctoral research associates in cutting edge research in nanoscience and nanotechnology.
This project has focused on determining the three dimensional structures of fullerenes and endohedral fullerenes though X-ray diffraction. These molecules involve closed cages of carbon atoms with a surface made up of 12 pentagons and a variable number of hexagons. The best known of these Buckyballs is C60, but larger cages with more carbon atoms can be made and we are particularly interesting in characterizing these larger fullerene cages. When atoms or groups of atoms are trapped within such a carbon cage, the resulting molecule is known as an endohedral fullerene. Empty cage fullerenes are being used as electron acceptors in solar energy storage devices, while endohedral fullerenes are being developed for biomedical applications such as relaxation agents for magnetic resonance imaging (MRI). We have pioneered in the use of cocrystallization utilizing a fullerene and a second molecule, generally a metalloporphyrin as a means of obtaining crystals suitable for single crystal X-ray diffraction. Our collaborative efforts have resulted in the structural characterization of a number of large endohedral fullerenes containing one or two samarium atoms. Of these, Sm2@C104 involves the largest fullerene cage to be structurally characterized to date. We have demonstrated the role of dioxygen in determining the course of reactions of Sc3N@C80 and have identified an endohedral fullerene with a fairly large whole in its framework that is produced by oxidation. We have identified a criterion, the maximal pentagon separation, as a determinant in fullerene cage structure that is applicable to endohedral fullerenes. This project has involved extensive collaborations with scientists in the U. S., Spain, China, and Japan. Much of this aspect of the project has been conducted through the exchange of samples of valuable chemical compounds and through communication via e-mail. Through their work on this project, our graduate students have learned methods of chemical synthesis, crystallization, and crystal growth. Some have become proficient in single crystal X-ray diffraction. Some have also become expert in the use of mass spectrometry. One student is involved with the preparation of complex mixtures of fullerenes and endohedral fullerenes and is studying means of exploring their chemical reactivity. Graduate students have learned how to interact with one another and how to acquire new techniques from their peers. They have leaned how to train undergraduates in scientific methodology and then utilize these undergraduate students and their newly learned skills to pursue their research projects.
