With this award from the Experimental Physical Chemistry program, the P.I., Professor Stephen Kukolich of the University of Arizona will modify and use a pulsed-beam, Fourier-transform microwave spectrometer to measure rotational transition frequencies for transition metal complexes, radicals, and other molecules in the 5 to 18 GHz region of the microwave spectrum. A new laser-photodissociation beam source will be constructed for measurements on organometallic radicals and their reaction products. This will allow more efficient and selective production of these radicals and reaction products, than most previous systems. The overall objectives of this work include measurements of the three-dimensional gas-phase structures, magnetic interaction parameters and quadrupole coupling strengths. These measurements are proposed for: a) transition metal radicals and reaction products involving these radicals, b) transition metal dihydrogen and dihydride complexes, and c) weakly-bound complexes with transition metal compounds. The magnetic interaction parameters and quadrupole coupling strengths directly characterize the electronic charge distributions. Quantum mechanical (Density Functional Theory) calculations will be carried out for all of the complexes studied. The coordination of experimental work with the theoretical calculations helps to make the measurements more efficient, improves our understanding of the electronic structure of molecules and provides guidelines and experimental examples for improvements in ab initio, quantum chemistry calculations. Transition metal complexes are very important in the chemical industry, in biological systems and as an area of study in inorganic chemistry. Millions of tons of chemical products are produced each year using reactions which involve transition metal catalysts. The active sites of many enzymes and transport proteins in living systems contain transition metal complexes. A large fraction of the research and study in inorganic chemistry is focused on transition metal complexes, and the proposed work will provide new contributions to the structural database that is used in research, industry and education. The proposed work will often involve smaller, ?model? complexes, but will provide results relevant to the larger, more complex systems. The accurate, three-dimensional structures for transition metal complexes, are helpful in understanding reaction mechanisms. Successful modeling of reaction mechanisms in chemistry and biology often depends on the accurate and reliable experimental structural information. Improving calculation methods and basis sets through correlation with new experimental data is useful because the calculations are presently the only source of detailed information on short-lived radicals or high-energy reaction intermediates. Studies of metal dihydrogen complexes may provide information which will be useful for improving hydrogen storage technology. Graduate and undergraduate research students will learn fundamentals of chemistry, quantum mechanics and methods and techniques involved in computer work, microwave electronics and making physical measurements through direct involvement in the proposed projects. Participation in the research by underrepresented minorities and a secondary school teacher, or non-Ph.D. college student will be actively sought for the proposed projects.
