Switching of functionalized azobenzene suspended between gold tips by mechanochemical, photochemical, and opto-mechanical means.

Optical, purely mechanical, and combined opto-mechanical switching cycles of a molecular switch embedded in a metal junction are investigated using density functional theory and (excited state) ab initio molecular dynamics. The nanomechanical simulations are done on realistic models of gold electrode tips bridged by a single dithioazobenzene molecule. Comparison of different tip models shows that the nature of the tips affects switching processes both qualitatively and quantitatively. The study predicts that purely photochemical cis⇌trans switching cycles of suspended azobenzene bridges are mechanically hindered; combined opto-mechanical as well as purely mechanochemical forward and backward switching is, however, feasible.