1/10 - Faculty Candidate Seminar (materials): Mark Chen, UC Berkeley
University of California, Berkeley
Host: Rob Knowles
Creating Utility from Ubiquity: Studies in Catalytic C-H Oxidation and Organic Solar Cells
Carbon-hydrogen bond functionalization and solar cell technology share a common goal of harnessing abundant and latent resources, for generating valuable chemical functionality and electricity, respectively. During my graduate studies, we developed Pd(II)/sulfoxide-catalyzed methods for oxidizing allylic C-H bonds. Branched allylic oxidation proceeded by a novel mechanism that we named Serial Ligand Catalysis, where two different ligands work with a single metal ion to promote separate product-forming steps. Towards targeting aliphatic C-H bonds, we discovered an electrophilic, bulky Fe(II) catalyst (Fe(PDP)) that promoted the selective oxidation of 3° and 2° C-H bonds. Site-selectivity was determined by substrate electronic, steric, and stereoelectronic effects or through the use of carboxylic acids as a directing group. This novel catalysis displayed remarkably predictable selectivity, even with the oxidation of complex natural products. During my postdoctoral research, we discovered that tuning conjugated polymer backbone coplanarity and solubility provided synthetic control for whether a polymer thin-film adopted face-on or edge-on orientation to the substrate. This control of solid-state properties has a dramatic effect on electronic device performance due to the anisotropic charge transport observed with conjugated polymers. Overall, this work reveals a powerful strategy for designing polymer-based photovoltaics with improved power conversion efficiency.