Optical resolution of oriented enantiomers via photodissociation: Quantum simulations for H2POSD

Abstract

We demonstrate quantum mechanically how to resolve enantiomers from an oriented racemic mixture taking advantage of photodissociation. Our approach employs a femtosecond ultraviolet (UV) laser pulse with specific linear polarization achieving selective photodissociation of one enantiomer from a mixture of L and D enantiomers. As a result, the selected enantiomer is destroyed in the electronic excited state while the opposite counter enantiomer is left intact in the ground state. As an example we use H2POSD which presents axial chirality. A UV pulse excites the lowest singlet excited state which has nσ* character and is, therefore, strongly repulsive along the P-S bond. The model simulations are performed using wavepackets which propagate on two dimensional potential energy surfaces, calculated along the chirality and dissociation reaction coordinates using CASSCF level of theory.