Ithaca College

Anna C. Brezny will present
Origins of Selectivity in the Oxygen Reduction Reaction

Kazimer L. Skubi will present
[2+2] Cycloadditions Using Visible Light Photoredox Catalysis

Tuesday, September 17th 12:10 pm in CNS 333
Pizza and Beverages Provided

Students are also invited to meet informally with the speakers at 4pm in the CNS 3rd floor Atrium.

The oxygen reduction reaction (ORR) is the reductive reaction in fuel cell technology and its selectivity for water over hydrogen peroxide is important. Iron porphyrin catalysts have long been studied for the ORR, but the origins of selectivity are still not well understood. Similar issues arise in catalysis with heme enzymes (e.g. cytochrome P450). In this work, we explore the production of H2O versus H2O2 in electrocatalytic ORR by iron tetramesitylporphyrin (Fe(TMP)). Based on experimental and computational results, we propose that selectivity is governed by competition between protonation of the Fe(TMP)(OOH) intermediate to produce water versus dissociation of an HOO– ligand leading to H2O2. The data rule out the commonly proposed mechanism that is suggested in enzymatic systems.

Photochemical reactions hold tremendous promise for organic synthesis. They are able to access mechanistic pathways that are unique from — and often complementary to — thermal reactions. However, synthetic photochemistry has traditionally been a niche field, in large part because of the need for specialized equipment and high-intensity UV light sources. Our research focuses on photoredox catalysis, in which transition metal complexes absorb visible light, then use its energy to perform single electron redox chemistry with organic substrates. In our case, this enables intermolecular [2+2] cycloaddition reactions with mild light sources, sensitive functional groups, and acyclic substrates.

Individuals with disabilities requiring accommodations should contact Paula Larsen at plarsen@ithaca.edu or (607) 274-3238. We ask that requests for accommodations be made as soon as possible.