Ultrafast Transversal CISS Effect Observed in a Chiral Photoswitching Molecule

Progress in the fundamental understanding of the chirality-induced spin-selectivity (CISS) effect is hindered by complexity of the systems that have been characterized experimentally. With the goal of emulating CISS in a sufficiently simple molecular system amenable to a high-level ab initio treatment, we introduce a small chiral molecule that supports local and charge-transfer excited states. The molecule can also act as a chiral photoswitch. Photoswitches with intramolecular charge-transfer are designed by connecting two equivalent chromophores through an electronically inert, prochiral structure. Time-dependent simulations with an effective Hamiltonian parametrized using equation-of-motion coupled-cluster calculations show that optical excitation induces transverse spin-polarization developing on a subpicosecond timescale, and we propose an experimental scheme for measuring it. Our simulations suggest that a purely electronic CISS effect, driven by spin–orbit coupling, is possible and that spin-polarization can be created in a chiral molecule without charge transfer.