Multistate Switching of Spin Selectivity in Electron Transport Through Light-Driven Molecular Motors

Abstract

It was established that electron transmission through chiral molecules depends on the electron’s spin. This phenomenon, termed the chiral-induced spin selectivity (CISS) effect has been observed in chiral molecules, supramolecular structures, polymers and metal-organic films. Which spin is preferred in the transmission depends on the handedness of the system and the tunneling direction of the electrons. Molecular motors based on overcrowded alkenes show multiple inversions of helical chirality under light irradiation and thermal relaxation. We show here multistate switching of spin selectivity in electron transfer through first generation molecular motors based on the four accessible distinct helical configurations, measured by magnetic-conductive atomic force microscopy. The efficient spin polarization observed in the photostationary state of the right-handed motor coupled with the modulation of spin selectivity through the controlled sequence of helical states opens opportunities to tune spin selectivity on-demand with high spatio-temporal precision. An energetic analysis correlates the spin injection barrier with the extent of spin polarization.

Keywords: Molecular motor, Spin polarization, CISS effect, Magnetic-conductive atomic force microscope, helix inversion