Reversible Photomechanical Switching of Individual Engineered Molecules at a Surface

TL;DR

This study demonstrates reversible light-induced mechanical switching of individual engineered azobenzene molecules on a gold surface, with enhanced activity achieved by attaching tert-butyl groups to modulate surface interactions.

Contribution

It introduces a method to reversibly switch molecular conformations on a surface using light, with engineered molecules showing increased activity through ligand modification.

Findings

Reversible switching between trans and cis states observed via STM.

Increasing tert-butyl groups enhances molecular photomechanical activity.

Surface coupling influences the efficiency of molecular switching.

Abstract

We have observed reversible light-induced mechanical switching for a single organic molecule bound to a metal surface. Scanning tunneling microscopy (STM) was used to image the features of an individual azobenzene molecule on Au(111) before and after reversibly cycling its mechanical structure between trans and cis states using light. Azobenzene molecules were engineered to increase their surface photomechanical activity by attaching varying numbers of tert-butyl (TB) ligands ("legs") to the azobenzene phenyl rings. STM images show that increasing the number of TB legs "lifts" the azobenzene molecules from the substrate, thereby increasing molecular photomechanical activity by decreasing molecule-surface coupling.