The mechanical properties of light-driven molecular switches as well as mechanically induced switching will be quantitatively determined on the single molecule level. Molecular switches, e.g. oligo-azobenzenes or conjugated π systems containing a predetermined breaking point and an arresting line will be synthesized, covalently linked between a surface and an AFM cantilever and subsequently strained in an atomic force microscope (AFM) with a constant force. Thus, reversible switching of conformational changes as well as electric current through a conducting molecule will be enabled. In a theoretical investigation, classical molecular dynamics will be combined with external force terms on a semi-empirical configuration-interaction level to simulate mechanochemistry and photoswitching under external strain.