Molecular Insights into Chiral-Induced Spin Selectivity: Exploring NO:2-Butanol Collision Complexes as Model Systems

Chiral-induced spin selectivity (CISS) describes a fundamental mechanism to control electron spin orientations in chiral environments. Characterizing theoretically-tractable benchmarks may lead to a molecular-scale interpretation of the underlying principles of CISS. Collision complexes between nitric oxide (NO) and 2-butanol were used as model systems to examine the possible effects of CISS in radical-molecule bimolecular collisions. Herein, IR action spectroscopy with 1+1 resonance-enhanced multiphoton ionization (REMPI) was used to record the IR spectrum of the NO:2-butanol complex. Furthermore, IR activation was combined with velocity map imaging (VMI) of NO products to reveal the dynamical outcomes following NO:2-butanol complex dissociation. In order to probe the population of NO spin-orbit states following IR activation of the collision complex, product state distributions were recorded to explore the plausible angular momentum pairing between the NO radical electron spin with the chiral 2-butanol partner. Experiments were performed on a racemic and enantiomerically pure (S enantiomer) sample of the NO:2-butanol complex. Differences between the two samples suggest that CISS effects may lead to the dynamical signatures observed between chiral enantiomers and NO quantum state configurations. We propose these preferences may be a result of two competing processes, wherein certain enantiomers of 2- butanol pair favorably or unfavorably with the radical electron spin of NO and the symmetry of its pi* molecular orbital.