Energetics of Molecular Complexes in a Supersonic Beam: A Novel Spectroscopic Tool for Enantiomeric Discrimination

Abstract

A subtle balance between attractive (electrostatic and dispersive) and repulsive (steric) forces is responsible for the different stabilities and spectral features of supersonically expanded van der Waals complexes between (R)-(+)-1-phenyl-1-propanol (R) and (R)-(−)- (r) or (S)-(+)-2-butanol (s). The homochiral Rr complex is more stable than the heterochiral Rs diastereomer in both the ground and excited states (see drawing). This was determined by the first direct measurement of the binding energies of the diastereomeric complexes by two color resonance two photon ionization/time-of-flight mass spectrometry.