Chirality and intermolecular forces: studies using R2PI experiments in supersonic beams

One- and two-color, mass-selected resonant two-photon ionization (R2PI) spe ctra of the S-1<-- S-0 transitions in the bare (R)-(+)-1-phenylethan-1-ol ( E-R) and its complexes with a solvent molecule (solv: (S)-(+)butan-2-ol (B- S), (R)-(-)butan-2-ol (B-R), or water (W)) have been recorded after a super sonic molecular beam expansion. The excitation spectrum of bare E-R conform s to theoretical predictions at the B3LYP/6-31G** level of theory by pointi ng to the formation of a single conformer. The one-color R2PI excitation sp ectra of the diastereomeric complexes [E-R-solv] (solv: B-S or B-R) are cha racterized by significant shifts of their band origin relative to that of b are E-R. The extent and the direction of these spectral shifts are found to depend upon the structure and the configuration of solv and are attributed to different short-range interactions in the ground and excited [E-R-solv] complexes. In analogy with strictly related diastereomeric complexes, the phenomenological binding energy of the homochiral [E-R-B-R] is found to be greater that of the heterochiral one [E-R-B-S]. The one-color R2PI excitati on spectra of the [E-R-W] complex displays two signals blue shifted by 54 a nd 73 cm(-1), relative to the S-1<-- S-0 band origin of bare E-R, which ind icate the presence of a O-H ...pi electrostatic interaction between E-R and W.