In this project funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professor Christopher J. Cramer of the Department of Chemistry at the University of Minnesota will employ computational/theoretical models to study mono- and polynuclear transition-metal complexes based on copper, iron, cobalt, and ruthenium, with the key focus being to characterize mechanistic details associated with their ability to catalyze reactions having special relevance to sustainability. Catalytic processes that will be assigned the highest priority for study include (i) the oxidation of otherwise unactivated C-H bonds, (ii) water oxidation to generate molecular hydrogen and oxygen, (iii) reduction of carbon dioxide. The first catalytic process provides access to high-value functionalized molecules from cheaper hydrocarbon feedstocks, the second is a reaction of key importance in the conversion of solar energy into a green chemical fuel (hydrogen), and the third offers the opportunity to convert cheap and abundant CO2 into industrially useful commodity chemicals like formaldehyde and methanol, which is of considerable interest not only from an economic perspective, but also because of the influence of increasing atmospheric CO2 levels on global climate change. Any locally developed code/software that implements new models will be made broadly available to the greater chemistry community, and ongoing incorporation of models into open source and commercial codes will further extend their availability. Outreach and mentoring activities will be accomplished through continued work with a number of University of Minnesota programs, including the College of Science & Engineering Summer Bridge Program, the Multicultural Summer Research Opportunities Program, and the North Star STEM alliance/Louis Stokes Alliances for Minority Participation program, amongst others.
Density functional and highly correlated single and multideterminantal wave function theories will be applied to complex chemical systems designed to catalyze reactions of interest from a sustainability standpoint. In order to treat the influence of a surrounding condensed phase on the catalytic cycle, continuum (and cluster-continuum) solvation models for use in both equilibrium and non-equilibrium situations (e.g., computations of standard reduction potentials and solvatochromic shifts, respectively) will be employed. Thermochemical and spectral quantities will be determined and validated against experimental data where available. High priority targets for study include water splitting focusing especially on catalysts based on earth-abundant metals, for which mechanistic details remain obscure in several systems based on copper or iron, for example. Reduction of carbon dioxide remains another challenging problem, particularly from a catalytic standpoint, and the ability of mono- and polynuclear transition-metal complexes to bind and activate CO2 to reduction will be examined in order to understand those electronic structure details (and how they are influenced by ligands) that facilitate reaction. Lastly, "green" oxidation reactions employing molecular oxygen as the oxidant and activating C-H bonds, for example, will be explored for systems where catalytic activity has been observed based on copper or manganese containing coordination compounds.
