Submolecular-scale control of phototautomerization

TL;DR

This paper demonstrates submolecular control of phototautomerization using an STM tip to manipulate light-matter interactions at the atomic scale, enabling precise regulation of reaction rates and populations.

Contribution

It introduces a novel method to control photochemical reactions at the atomic level by leveraging electromagnetic field confinement at the STM tip apex.

Findings

Controlled phototautomerization rate via laser wavelength tuning.

Manipulated tautomer population with tip positioning.

Achieved sub-molecular precision in photochemical control.

Abstract

Many natural and artificial reactions including photosynthesis or photopolymerization are initiated by stimulating organic molecules into an excited state, which enables new reaction paths. Controlling light-matter interaction can influence this key concept of photochemistry, however, it remained a challenge to apply this strategy to control photochemical reactions at the atomic scale. Here, we profit from the extreme confinement of the electromagnetic field at the apex of a scanning tunneling microscope (STM) tip to drive and control the rate of a free-base phthalocyanine phototautomerization with submolecular precision. By tuning the laser excitation wavelength and choosing the STM tip position, we control the phototautomerization rate and the relative tautomer population. This sub-molecular optical control can be used to study any other photochemical processes.