Research Highlights
Cushing Lab
Determining Quasi-Equilibrium Electron and Hole Distributions of Plasmonic Photocatalysts Using Photomodulated X-ray Absorption Spectroscopy
Most photocatalytic and photovoltaic devices operate under broadband, constant illumination. Electron and hole dynamics in these devices, however, are usually measured by using ultrafast pulsed lasers in a narrow wavelength range. In this work, we use excited-state X-ray theory originally developed for transient X-ray experiments to study steady-state photomodulated X-ray spectra.
Kornfield Lab
Mist-control of polyalphaolefin (PAO) lubricants using long pairwise end-associative polymers
Accidental release of pressurized hydrocarbon fuels and lubricants are a major fire hazard due to the formation of small droplet mists that can readily evaporate and ignite. Mist control through increasing droplet size and suppressing droplets has been previously demonstrated with high molecular weight polymer additives, but traditional long polymer additives do not survive the pumping that would usually precede accidental release. This constraint inspired associative polymer additives that can transiently form the high molecular weights needed for mist control, while reversibly breaking during pumping. A prior study demonstrated the efficacy of such a system in fuel: long telechelic polycyclooctadiene (PCOD) with pairwise associating acid and base end-groups.
Peters Group
Intermolecular Proton-Coupled Electron Transfer Reactivity from a Persistent Charge-Transfer State for Reductive Photoelectrocatalysis
Interest in applying proton-coupled electron transfer (PCET) reagents in reductive electro- and photocatalysis requires strategies that mitigate the competing hydrogen evolution reaction. Photoexcitation of a PCET donor to a charge-separated state (CSS) can produce a powerful H-atom donor capable of being electrochemically recycled at a comparatively anodic potential corresponding to its ground state. However, the challenge is designing a mediator with a sufficiently long-lived excited state for bimolecular reactivity. Here, we describe a powerful ferrocene-derived photoelectrochemical PCET mediator exhibiting an unusually long-lived CSS (τ ∼ 0.9 μs). In addition to detailed photophysical studies, proof-of-concept stoichiometric and catalytic proton-coupled reductive transformations are presented, which illustrate the promise of this approach.
Stoltz Group
Enantioselective Total Synthesis of (−)-Hunterine A Enabled by a Desymmetrization/Rearrangement Strategy
The first enantioselective total synthesis of (−)-hunterine A is disclosed. Our strategy employs a catalytic asymmetric desymmetrization of a symmetrical diketone and subsequent Beckmann rearrangement to construct a 5,6-α-aminoketone. A convergent 1,2-addition joins a vinyl dianion nucleophile and the enantioenriched ketone. The endgame of the synthesis features an aza-Cope/Mannich reaction and azide-olefin dipolar cycloaddition to complete the pentacyclic ring system. The synthesis is completed through a regioselective aziridine ring opening.