Spin Filtering with Surface-Active Helicene- and Twistacene-Based Perylene Diimides

Creating new chiral molecular and macromolecular systems that can polarize the spin of electrons has the dual promise of both applications in spintronics and a fundamental understanding of their origins. Here, we put forward two optically active helical ladder dimers from perylene diimide-based twistacenes and helicenes. We detail a scalable method to separate the helices for each of these systems and methods to functionalize them with thiol groups that allow for self-assembled monolayer formation on metal surfaces. We probed these monolayers with conductive atomic force microscopy, revealing that they are highly conductive. If the substrate is magnetized, then the current we measure with conductive atomic force microscopy is controlled by the handedness of the helices used to form the monolayers. Furthermore, helices of the same handedness for either the twistacene or helicene (right-handed helices vs left-handed helices) produce high (or low) currents in devices with the same magnetization. Importantly, we find a correlation between the magnetic field dependence of the conductivity and the helicity of the molecules, suggesting a link between these two properties, independent of the sign of their electronic circular dichroism.