Schneider, Patrick E.

DOE OSTI2021

Electrocatalytic Oxidation of Alcohol with Cobalt Triphosphine Complexes

Coordination of the tridentate ligand bis(2-diphenylphosphinoethyl)phenylphosphine (P3) to cobalt forms [(CH3CN)2CoIIP3](BF4)2 (CoIIP3). In the presence of the Brönsted base iPr2EtN, CoIIP3 electrocatalytically oxidizes benzyl alcohol (BnOH) to benzaldehyde at an applied potential of -630 mV vs Fc+/0 with a TON of 19.9. In a noncatalytic reaction with excess BnOH and iPr2EtN, CoIIP3 is reduced by one electron to [(CH3CN)2CoIP3]BF4 (CoIP3) with concomitant formation of half an equivalent of benzaldehyde. This stoichiometric oxidation of BnOH suggests electron transfer occurs between intermediate cobalt species and starting CoIIP3. Kinetics and computational studies support an unfavorable alcohol binding preequilibrium step followed by favorable deprotonation of bound alcohol.

Electrocatalysis, Alcohol oxidation, Electrooxidat↗

DOE OSTI2020

Nuclear-Electronic Orbital Ehrenfest Dynamics

The recently developed real-time nuclear-electronic orbital (RT-NEO) approach provides an elegant framework for treating electrons and selected nuclei, typically pro- tons, quantum mechanically in nonequilibrium dynamical processes. However, the RT-NEO approach neglects the motion of the other nuclei, preventing a complete de- scription of the coupled nuclear-electronic dynamics and spectroscopy. In this work, we describe the dynamical interaction between the other nuclei and the electron-proton subsystem with the mixed quantum-classical Ehrenfest dynamics method. The NEO- Ehrenfest approach propagates the electrons and quantum protons in a time-dependent variational framework, while the remaining nuclei move classically on the correspond- ing average electron-proton vibronic surface. This approach includes the non-Born- Oppenheimer eects between the electrons and quantum protons with RT-NEO and between the classical nuclei and the electron-proton subsystem with Ehrenfest dynam- ics. Spectral features for vibrational modes involving both quantum and classical nuclei are resolved from the time-dependent dipole moments. Moreover, nuclear quantum ef- fects are included directly in nonadiabatic dynamics simulations. The excited state intramolecular proton transfer in the o-hydroxybenzaldehyde molecule is shown to be faster and to exhibit a larger kinetic isotope eect with NEO-Ehrenfest compared to classical Ehrenfest dynamics. This work shows that the NEO-Ehrenfest method is a powerful tool to study dynamical processes with coupled electronic and nuclear degrees of freedom.

Zhao, Luning↗