Dr. Billups' research covers a variety of areas in organic chemistry, including the synthesis and properties of small ring alkenes and bicycloalkenes, fullerenes, single-wall carbon nanotubes, and products formed at low temperature from the reactions of transition metal atoms and small organic molecules. Work has also been initiated on the nucleation, growth, and structure of gas hydrates, materials that cause serious problems in long distance natural gas pipelines.
A major focus of his research during the past few years has been the development of a vacuum gas phase procedure for the synthesis of small ring cycloalkenes and bicycloalkenes using reagents adsorbed on inert surfaces to effect elimination reactions. This approach allows the reactive species to be isolated at low temperature, and eliminates many of the undesired bimolecular side reactions that would normally be encountered in solution. Energetic compounds can thus be collected readily in cold traps for further chemical studies or spectral characterization. X-ray structural parameters of unstable low melting compounds are secured in collaboration with Dr. Roland Boese in Essen, Germany. Representative molecules whose syntheses have been accomplished include methylenecyclopropene, spiropentadiene, spiroheptatriene, and oxaspiropentene.
Studies in aromatic chemistry focus primarily on the dicycloproparenes, fullerenes, and single-wall carbon nanotubes. The synthesis of ladder polymers composed primarily of six-membered rings using dicycloproparenes as starting materials has been achieved. New materials that might result from these studies include polyacenes, polyphenanthrenes, novel graphite-like molecules with holes and other supramolecular systems. Current studies in the fullerene area involve the synthesis and characterization of the highly reduced fullerenes. 3He NMR spectroscopy plays an important role in the characterization of these materials. These studies are carried out in collaboration with Professor Martin Saunders at Yale University. Extensive studies on the sidewall functionalization of carbon nanotubes by free radicals are underway. Reactions of carbon nanotubes in oleum and sulfuric acid are also under investigation.
A final area involves studies on the activation of carbon-hydrogen bonds by first row transition metals. For example, photoexcited cobalt atoms have been found to insert into the carbon-hydrogen bonds of methane to yield CH3CoH. This same species can be microsynthesized and characterized using FTIR spectroscopy by cocondensing the metal with CH2N2, H2, and argon at 11 K. Photolysis of CH3CoH using 400 nm light leads to extrusion of the metal with the formation of the spectroscopically detectable Co(CH4) sigma complex shown to have C3v symmetry. Photolysis of this complex using a UV source regenerates the insertion product CH3CoH. Deuterium labeling studies have shown that the methane rotates freely on the cobalt.
Speaking in the symposium on Carbon Nano Structures & Devices.