Seth Brown

Developing Catalysis for Energy and the Environment Enhancing our understanding of the mechanisms of chemical reactions is critical to improve processes that interconvert between chemical and electrical energy or to make chemical products in a selective and environmentally benign way. The Brown group is addressing this general problem by making new inorganic or organometallic complexes with the aim of achieving reactivity through novel mechanisms. Traditionally, oxidation-reduction reactions mediated by metal-containing compounds involve changes in both the oxidation state and bonding that directly involve those metal centers. We are exploring an alternative mode of redox reactivity, what we term "nonclassical" redox reactions, where bond-making or bond-breaking events occur at a metal center but oxidations or reductions occur not at the metal center but at redox-active ligands attached to the metal. These processes generate novel species with unusual electronic structure, which may be capable of unusual reactivity. Furthermore, separating the locus of electron transfer from that of changes in bonding mimics the heterogeneous catalysis involved in fuel cells, suggesting that nonclassical homogeneous reactions may lead to conceptual insights or practical advances in systems for interconverting electrical and chemical energy. In some cases, we have observed reactions where both the oxidation state changes and the bonding changes take place at the ligand rather than the metal. This has allowed us to observe reactions at coordinatively saturated or even encapsulated metal centers that would normally be considered poor choices as catalysts because of the unavailability of open sites at the metal. We are currently engaged in elucidating the effect of the metal-ligand bonding on this ligand-centered reactivity and using that information to design new catalysts with enhanced reactivity, selectivity, or durability.

Nugraha, K.; Do, T. H. and Brown, S. N. "Bis(Iminoxolene)Iridium Complexes Over Four Oxidation States: From Sodium-Iridium Bonding to Ligand-Centered Radicals" 2025 Dalton Transactions, 54 (14), pp.5896–5905. DOI: 10.1039/d5dt00244c. Meissner, M.; Nugraha, K.; Grandstaff, K. D.; Do, T. H.; Jiménez, C. A.; Chin, W. Y.; Farrell, L. E.; Nguyen, P. D. and Brown, S. N. "Bis(Iminoxolene)Iridium Anion and Alkyls: How does Ligand Redox Noninnocence Interface with Oxidative Addition?" 2025 Organometallics, 44 (6), pp.760–775. DOI: 10.1021/acs.organomet.4c00514. Ayson, P. and Brown, S. N. "Anisotropic Π Bonding in Bis(Iminoxolene)Ruthenium: Consequences for Alkene and Alkyne Binding" 2024 Organometallics, 43 (17), pp.1889–1903. DOI: 10.1021/acs.organomet.4c00259. Carbonel, H.; Mikulski, T. D.; Nugra