1. Electrocatalysis: Linking Renewable Energy with Chemical Energy
Protons (H+), electrons (e–), and hydrogen (H2) are at the heart of a renewable energy economy. In addition to directly using H2 as a fuel, it can also be combined with N2 or CO2 to yield energy dense liquid fuels. When coupled with intermittent renewables (solar, wind, tidal, etc.), these processes do not rely on energy derived from fossil fuels.
How do we move around protons, electrons, and small molecules with precision and efficiency? By using electrocatalysts! This project focuses on designing new molecular electrocatalysts with proton-responsive ligands and explores their reactivity with (H+), electrons (e–), CO2, H2, and other small molecules to generate chemical fuels. With sustainability in mind, the group focuses on using Earth-abundant metals to achieve this goal. This is partly inspired by enzymes found in Nature that solely use abundant elements to tackle challenging chemical reactions with ease.
Recent Publications:
P. Sánchez, B. Goel, H. Neugebauer, R. A. Lalancette, S. Grimme, A. Hansen, D. E. Prokopchuk “Ligand Protonation at Carbon, not Nitrogen, During H2 Production with Amine-Rich Iron Electrocatalysts” Inorg. Chem. 2021, 60, 17407. 10.1021/acs.inorgchem.1c03142
2. Measuring Bond Strengths in Transition Metal C-H Activation Models
Homogeneous transition metal catalysts selectively functionalize C-H bonds to produce pharmaceutical and agricultural compounds while petroleum refining employs heterogeneous catalysts to process hydrocarbons on a massive industrial scale. In these processes, C(sp3)-H bond scission is an elementary (and often rate limiting) step during catalysis, but little is known about the magnitude of C-H bond weakening prior to bond cleavage. We have developed a new method of measuring the strength of C(sp3)-H bonds coordinated to transition metals (i.e. agostic interactions). To stabilize these agostic intermediates, our method uses a tridentate pincer ligand which serves as a C-H activation model to measure C-H acidity (pKa) and bond dissociation free energy (BDFE).
Recent Publications:
L. Lin, D. M. Spasyuk, R. A. Lalancette, D. E. Prokopchuk “Coordination-Induced Weakening of a C(sp3)-H Bond: Homolytic and Heterolytic Bond Strength of a CH-Ni Agostic Interaction” J. Am. Chem. Soc. 2022, 144, 12632. 10.1021/jacs.2c05667
3. Synthesis and Reactivity of Metalloradicals
Many enzymes rely on redox-active metalloradical intermediates to mediate the activation of H2, N2, and C-H bonds. However, activating such bonds using synthetically tractable Earth-abundant metalloradicals remains limited in scope and the Prokopchuk group is interested in synthesizing low-valent metalloradicals that homolytically activate C-H, N-H, and H-H bonds. We recently reported rare redox-active Mn(0) metalloradical which have been characterized via cyclic voltammetry, EPR spectroscopy, DFT, and single crystal X-ray diffraction. Reactivity studies are ongoing with these and other metalloradical platforms.
Recent Publications:
A. Karagiannis, A. M. Tyryshkin, R. A. Lalancette, D. M. Spasyuk, A. Washington, D. E. Prokopchuk “A Redox-active Mn(0) Dicarbene Metalloradical” Chem. Commun. 2022, 10.1039/D2CC04677F
The Prokopchuk Group thanks the below external funding agencies for support:
