Simultaneously probing two ultrafast condensed-phase molecular symmetry breaking events by two-dimensional infrared spectroscopy

摘要

In condensed phases, a highly symmetric gas-phase molecule lowers its symmetry under perturbation of the solvent, which is vital to a variety of structural chemistry related processes. However, the dynamical aspects of solvent-mediated symmetry-breaking events remain largely unknown. Herein, direct evidence for two types of solvent-mediated symmetry-breaking events that coexist on the picosecond timescale in a highly symmetric anion, namely, hexacyanocobaltate, is presented: 1) an equilibrium symmetry-breaking event in which a solvent-bound species having lowered symmetry undergoes a population exchange reaction with the symmetry-retaining species; 2) a dynamic symmetry-breaking event that is composed of many dynamic population-exchange reactions under fluctuating solvent interactions. Ultrafast two-dimensional infrared spectroscopy is used to simultaneously observe and dynamically characterize these two events. This work opens a new window into molecular symmetry and structural dynamics under equilibrium and non-equilibrium conditions.