Ultrafast Transversal CISS Effect Observed in a Chiral Photoswitching Molecule

Progress in fundamental understanding of the chirality-induced spin-selectivity (CISS) effect is hindered by complexity of the systems that have been characterized experimentally. With a goal to emulate CISS in a sufficiently simple molecular system amendable 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. The molecular design of photoswitches with intramolecular charge-transfer involves connecting two equivalent chromophores through an electronically inert, prochiral structure. Using time-dependent simulations with an effective Hamiltonian parameterized using equation-of-motion coupled-cluster calcu- lations, we show that optical excitation induces transverse spin-polarization developing on a sub-picosecond timescale and propose an experimental scheme for measuring it. The simulations suggest that 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.