Vibrational relaxation and microsolvation of DF after F-atom reactions in polar solvents

Solvent-solute interactions influence the mechanisms of chemical reactions in solution,but the response of the solvent is often slower than the reactive event. Here, we reportthat exothermic reactions of fluorine (F) atoms in d₃-acetonitrile and d₂-dichloromethaneinvolve efficient energy flow to vibrational motion of the deuterium fluoride (DF) productthat competes with dissipation of the energy to the solvent bath, despite strongsolvent coupling. Transient infrared absorption spectroscopy and molecular dynamicssimulations show that after DF forms its first hydrogen bond on a subpicosecond timescale, DF vibrational relaxation and further solvent restructuring occur over more than10 picoseconds. Characteristic dynamics of gas-phase F-atom reactions with hydrogencontainingmolecules persist in polar organic solvents, and the spectral evolution of the DFproducts serves as a probe of solvent reorganization induced by a chemical reaction.