Induced Photoelectron Circular Dichroism as a Probe for Distinguishing Diastereotopic Lone Electron Pairs

The hydrogen-bonded complexes of phenol with the chiral molecule methyloxirane (MOx) have been studied under supersonic jet conditions by photoelectron circular dichroism (PECD) experiments based on a resonance-enhanced two-photon ionization scheme. Ionization of the achiral phenol moiety within the complex leads to a strong photoelectron circular dichroism signal, due to chirality induction from the methyloxirane. We observe and characterize two conformers of the complex by IR-UV spectroscopy. They show PECD of similar magnitude and opposite in sign, which is explained in terms of a pseudo-enantiomer relation between them due to the complexation with one or the other of the two lone electron pairs of the MOx oxygen atom, leading to opposite out-of-plane deformation of the phenol hydroxyl group. Chirality indicators are used to quantify the chirality of the wave function localized on phenol. It is therefore possible to differentiate two diasterotopic electron lone pairs by chiroptical spectroscopy in the gas phase.