Electronic and infrared spectroscopy of jet-cooled (±)-cis-1-amino-indan-2-ol hydrates

Abstract

The role of conformational isomerism in molecular interaction has been studied using the example of jet-cooled complexes of (±)-cis-1-amino-indan-2-ol with water. The two formerly evidenced conformers of (±)-cis-1-amino-indan-2-ol easily form hydrates and dihydrates, which have been studied by means of laser-induced fluorescence and IR/UV double resonance spectroscopy, as well as ab initio calculations. All the 1 : 1 and 1 : 2 complexes with water evidenced in this work involve “ring” structures, in which the water monomer or dimer acts as an acceptor from the NH₂ and a donor to the OH groups of (±)-cis-1-amino-indan-2-ol. However, the water lies externally to the indan frame in the hydrates of conformer I of (±)-cis-1-amino-indan-2-ol, which possesses axial NH₂ and equatorial OH groups, and above it for the hydrates with the less stable conformer II, with equatorial NH₂ and axial OH groups. Consequently, the different steric constraints which exist in the two conformers result in different hydrogen bond topologies, with an additional OH⋯π interaction for the hydrates of conformer II.