Chiral aggregates of indan-1-ol with secondary alcohols and water: Laser spectroscopy in supersonic beams

Abstract

One color, mass selected resonant two-photon ionization (1cR2PI) spectra of supersonically expanded bare (R)-(−)indan-1-ol (I_R) and its complexes with chiral and achiral molecules (solv) have been investigated. The excitation spectrum of bare I_R has been analyzed and discussed on the basis of theoretical predictions at the B3LYP/6-31G** level of theory. The excitation spectra of its diastereomeric complexes with (R)-(−)-and (S)-(+)hexan-2-ol (X_R or X_S, respectively) and water (W) are characterized by significant shifts of their S₀ ← S₁ band origin relative to that of bare I_R. The extent and the direction of these 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 [I_R·solv] complexes. In particular the [I_R·W]_n complexes display band origins blue-shifted relative to that of bare I_R, attributed to the presence of an O–H⋯π electrostatic interaction between I_R and W in [I_R·W]_n. The [I_R·X_R] and [I_R·X_S] equilibrium structures have been calculated by a molecular dynamical (MM3) sampling and PM3 semiempirical local optimization.