Laser spectroscopy of clusters. Application to differentiation of chiral systems

Laser spectroscopic studies of isolated clusters formed in supersonic beams coupled to resonance enhanced multiphoton ionization, have demonstrated the potentiality of this method to obtain information on the physicochemical properties of a large variety of clusters. We have recently applied this laser supersonic jet technique to study chiral molecules and to enantiodifferentiation their omo and eteroclusters. In this paper, results on measurements of the binding energy of diastereomeric complexes of an aromatic chiral alcohol, the (R)-(+)-1-phenyl-1-propanol PR, with chiral sec-butanol S or R, n-butanol: N and H2O are reported. It is shown that their binding energies range around 5-6 kcal/mol. Semiempirical calculations confirm that the difference in binding energy of these clusters depends on a balance between electrostatic and dispersive forces.