New Photomechanical Molecular Switch Based on a Linear π‑Conjugated System

We report the electron-transport properties of a new photoaddressable molecular switch. The switching process relies on a new concept based on linear π-conjugated dynamic systems, in which the geometry and, hence, the electronic properties of an oligothiophene chain can be reversibly modified by the photochemical trans–cis isomerization of an azobenzene unit fixed in a lateral loop. Electron-transport measurements through self-assembled monolayers on gold, in contact with an eGaIn top contact, showed switching with a conductance ratio of up to 103. Ab initio calculations were used to identify the most energetically stable conformations of the molecular switch; the corresponding calculated conductances qualitatively explain the trend observed in the photoswitching experiments.