Femtosecond laser-driven enantioselectivity on achiral-chiral polymorphic transition

Enantioselective crystallization is commonly controlled during nucleation from solutions. Here, we propose a facile approach to realize the enantioselective polymorphic transition of crystals in a dry state via intense femtosecond (fs)-pulsed laser irradiation. A dried metastable achiral crystal of sodium chlorate is utilized as a starting target. When circularly polarized (CP) fs laser pulses with a high repetition rate are tightly focused on the surface of the achiral crystal, a polymorphic transition to the stable chiral crystal is trig-gered at the focal spot. The chiral crystal is outwardly expanded even after the laser is ceased and eventually replaces the entire achi-ral crystal. The crystal enantiomeric excess achieves more than 20%, suggesting that the handedness of the CP light causes a chiral bias for the enantioselective polymorphic transition. The dynamics and mechanism of the enantioselective polymorphic transition are dis-cussed based on the helical optical force exerted during the poly-morphic transition process.