Molecular Chirality and Charge Transfer through Self-Assembled Scaffold Monolayers

The effect of molecular chirality on electron transmission is explored by photoelectrochemistry. Thiol-terminated chiral scaffold molecules containing a porphyrin chromophore were self-assembled on gold surfaces to form a monolayer. Incorporation of the SAM-coated gold into an electrochemical cell and illumination with visible light generated a cathodic photocurrent. When using circularly polarized light, the photocurrent displayed an asymmetry (different magnitude of photocurrent for right versus left polarization) that changed with the molecular chirality (left- or right-handedness of the scaffold). A symmetry constraint on the electronic coupling between the porphyrin and the organic scaffold is proposed as a possible mechanism for the photocurrent asymmetry.