  We report the electronic transport properties of a new photo-addressable
molecular switch. The switching process relies on a new concept based on linear
{\pi}-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, contacted with eGaIn top contact, show switching with a conductance
ratio up to 1E3. Ab initio calculations have been used to identify the most
energetically stable conformations of the molecular switch, the corresponding
calculated conductances qualitatively explain the trend observed in the
photo-switching experiments.
