Single Molecule Conformational Change Driven by Overtone Absorption in a Laser-coupled Scanning Tunneling Microscope

Excitation of vibrational overtones in molecules has been shown to selectively drive molecular transformations, including conformational change, isomerization, bond rotation, and bond dissociation. As such, interest in overtone chemistry has grown in different fields, such as atmospheric chemistry and photocatalysis, to better understand how photon absorption affects molecular reactivity. In this talk, I will discuss our recent advances in using a laser-coupled scanning tunneling microscope (STM) to probe the conformational change of single molecules adsorbed on a metal substrate. The STM is used to monitor the change in conformation of individual molecules while the photon wavelength is varied within the visible to near-IR range. In our studies, the kinetics and equilibrium constant of the reversible conformational change can be directly determined. By using the topographic capabilities of the STM, we can also directly measure how this conformational change is affected by the heterogeneity of the molecule’s local environment.