Conformational equilibria, non-bonding interactions and chirality from rotational spectroscopy

The aim of this thesis is to characterize the genuine nature of the non-bonding interactions, such as hydrogen, weak hydrogen and halogen bonding as well as the lone pair•••π interaction, in an environment free from solvent or matrix effects, by using rotational spectroscopy in supersonic expansion. Fluorination and methylation effects, competition between different non-covalent interactions, isomeric preferences are described in the molecular system studied as well as the proton transfer process, the Ubbelohde and the reverse Ubbelohde effects, the internal rotations, and quadrupole couplings which take place. The dissociation energies of the molecular adducts are also estimated and the structural determination of molecules and/or molecular complexes is performed by using isotopologue spectra. Conformational and tautomeric equilibria are investigated for molecules of biological interests, occasionally using the laser ablation technique. Studies have been performed in order to differentiate the enantiomers of chiral molecules, based on opposite phase detection in double quantum coherence experiments.