Steric effects in light-induced solvent proton abstraction

In this collaboration, MSU Foundation Professor and University Distinguished Chemistry Professor Marcos Dantus and co-workers, including Professors Gary Blanchard, Babak Borhan, James Jackson, and Piotr Piecuch, and students in their groups, Jurick Lahiri and Jessica Kline from the Dantus group, Mehdi Moemeni from the Borhan group, and Ilias Magoulas and Stephen Yuwono from the Piecuch group, examine steric issues with solvent proton abstraction by the excited Schiff base FR0-SB. Proton transfer is efficient for primary alcohols, and greatly diminished for secondary alcohols, consistent with high-level quantum chemistry calculations. Proton transfer occurs when molecules achieve spatial proximity and alignment with the Schiff base imine lone pair. Interestingly, the proton transfer rate increases with decreasing temperature, revealing a significant entropic contribution, and electronic structure calculations require at least three explicit solvent molecules to enable proton transfer. These results provide new, fundamental insight into photoinitiated proton exchange.

J. Lahiri, M. Moemeni, I. Magoulas, S. H. Yuwono, J. Kline, B. Borhan, P. Piecuch, J. E. Jackson, G. J. Blanchard and M. Dantus

Phys. Chem. Chem. Phys., 2020, 22, 19613.

DOI: 10.1039/D0CP03037F