Advancing Our Knowledge of the Transition Metal-Carbon Bond: Integrating Spectroscopy and Theory

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With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program in the Division of Chemistry, Lucy Ziurys of the University of Arizona and Nathan DeYonker of University of Memphis, respectively, are combining experimental and computational methods to explore the ground electronic states of small molecules containing transition metals. Transition metals play a prominent role in catalysis and biochemistry, but the fundamental properties of chemical bonds between transition metals and carbon remains elusive. Even with modern-day, high-level computer modeling methods, it is difficult to predict the chemical bonding properties of the even simplest metal-carbon bonds. The Ziurys and DeYonker team will work to advance the understanding of transition metal chemistry through the development of sophisticated quantum computational techniques to accurately predict molecular properties of metal-containing species, while using high-resolution spectroscopic measurements to validate the theoretical results. Their discoveries could lead to a better understanding of catalysts used in future clean energy generation and storage applications, as well as the development of new materials with special polymeric or magnetic properties. A diverse group of students at the graduate and undergraduate levels will participate in the project. They will receive valuable training in modern experimental and computational methods and fully participate in the scientific discovery process.High-resolution, gas-phase rotational spectroscopy techniques will be employed in the 4 GHz-850 GHz range to investigate chemical bonding in metal carbide and acetylide species. Metals of interest include Ni, Co, Ti, and Fe. Both millimeter/sub-mm direct-absorption and Fourier transform microwave (FTMW) methods will be used, coupled with well-developed gas-phase synthetic techniques aimed at creating novel, reactive species. The experimental work will be carried out in tandem with ab initio calculations that involve higher-order, single reference coupled cluster and multireference configuration interaction theories. This combined approach will establish the composition of molecular orbitals, bond types, the ground state and the complex manifold of low-lying excited states, spin-orbit effects, and static electron correlations. Many of the targeted species are open-shell and involve spin-orbit and spin-spin couplings, as well as nuclear spin interactions, and thus are challenging both experimentally and computationally. A major goal is to provide predictive theoretical electronic and spectroscopic properties applicable to larger metal-carbon containing molecules relevant to many fields of chemistry, including catalysis, synthesis, materials chemistry, and chemical biology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.