Organometallic Chemistry of Periodic pi-Electron Surfaces: Carbon Nanotubes and Graphene

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TECHNICAL SUMMARY:This project, supported by the Solid State and Materials Chemistry Program, involves preparation of a new class of graphitic materials in which the surfaces are functionalized with transition metals, thereby allowing the formation of atomic scale interconnects that consist of bis-hexahapto-metal-bonds between the benzenoid ring systems; this approach is anticipated to provide a method to increase the dimensionality of the electronic structure of the 1-D carbon nanotubes and the 2-D graphene sheets. Preliminary experiments show that chromium complexes are accessible by a wide range of preparative methods, which include solution phase functionalization with chromium carbonyl precursors, solid state thermal reactions under pressure beginning with mono-hexahapto complexes and gas phase metal vapor synthesis using electron beam physical vapor deposition (e-beam). All of these materials show evidence of a change in the electrical conductivities of the starting graphitic structures on organometallic functionalization and it is the purpose of this proposal to broaden the fundamental understanding of the interaction between metals and graphene surfaces and to refine the synthesis and physical characterization of the materials. Based on a frontier molecular orbital analysis of the electronic structure of graphene at the Dirac point, graphene is identified as an excellent ligand in coordination complexes and it is apparent that a wide variety of organometallic intercalation compounds can be prepared. Thus the goal of the proposed research is to develop a class of novel transition metal-graphene materials that exhibit unique electronic properties and to lay the foundation for electronic interconnects between graphitic surfaces at the atomic level. The new materials may be of interest as the active constituent in electronic, opto-electronic and spintronic devices. NON-TECHNICAL SUMMARY:This project will lead to a new class of carbon nanotube and graphene frameworks that are held together by covalent, rather than ionic bonding. The proposed materials are expected to have novel catalytic, electronic and magnetic properties; a number of the known charge transfer graphite compounds exhibit superconductivity and such a possibility exists with the proposed organometallic compounds. The broader impact of this project will be most evident in the participation and training of students at the undergraduate and graduate level which will occur in a highly integrated, multidisciplinary program whose work is directed toward advancements in fundamental and technologically significant aspects of the chemical sciences. The students will be exposed to an extensive suite of modern research tools and will become familiar with the Center for Nanoscale Science and Engineering nanofabrication tools and analytical techniques. We have found that such training serves as an invaluable asset for students that are seeking entry into the electronics industry. Special effort will be devoted to attracting women and minorities into the research program through the California Alliance for Minority Participation (CAMP), the Summer Bridge Research Program and CNAS Dean Summer Internships. This project is supported by the Solid State and Materials Chemistry Program.