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.
@article{arxiv.cond-mat/0612201,
title = {Reversible Photomechanical Switching of Individual Engineered Molecules at a Surface},
author = {Matthew J. Comstock and Niv Levy and Armen Kirakosian and Jongweon Cho and Frank Lauterwasser and Jessica H. Harvey and David A. Strubbe and Jean M. J. Frechet and Dirk Trauner and Steven G. Louie and Michael F. Crommie},
journal= {arXiv preprint arXiv:cond-mat/0612201},
year = {2011}
}