Molecular electronic chirality in copper phthalocyanine induced via twisted π-π stacking on bilayer graphene

Electronic chirality within single molecules constitutes an intriguing phenomenon in quantum chemistry, whose inducing mechanism however remains underexplored. Here, we report a distinct formation mechanism for electronic chirality in CuPc molecules adsorbed on bilayer graphene on highly oriented pyrolytic graphite, as incurred via twisted π-π stacking. Scanning tunneling microscopy measurements unveil that CuPc molecules exhibit prominent chirality in morphology at low biases, but restore their D4h symmetry at large biases, demonstrating the chirality is electronic origin. With tip manipulations, the two enantiomers of CuPc can be reversibly switched. Density functional theory calculations reveal that the electronic chirality arises from π-π hybridization between CuPc and graphene, leading to asymmetric charge distribution. The chiral configuration is determined by adsorption sites and rotation angles relative to graphene, in agreement with experimental observations. This work uncovers a π-π hybridization mechanism for driving electronic chirality, providing a platform for designing chiral molecular electronic devices. Electronic chirality is a fascinating but still poorly understood phenomenon. Here, the authors show that CuPc molecules on bilayer graphene exhibit electronic chirality driven by twisted π–π interactions, which can be reversibly switched using an STM tip.