Bridging conformational preferences and non-covalent interactions across diverse cyclic structures: An in-depth exploration through rotational spectroscopy and computational calculations in isolated phase

Abstract

Determining molecular conformations is fundamental to understanding the intricate relationship between the structure of a molecule and its physicochemical characteristics, such as energy, reactivity, and functionality. However, assessing the energy associated with a molecular conformation poses difficulties, especially in multi-conformational systems where each one can assume numerous energy minima. These flexible molecular systems involve a complex interplay of intramolecular forces competing for dominance. Cyclic molecules are of great scientific interest because they are a prime example of molecular flexibility and due to their vital roles in both chemistry and biology. As with any molecule relevant to biological processes, it is widely recognised that the structural arrangements adopted by these compounds directly influence their physico-chemical functions and characteristics. It is therefore of vital importance to elucidate the conformational preferences of these molecules by means of techniques capable of discerning between a wide variety of possible conformations. In this thesis it will be addressed the elucidation of the three-dimensional (3D) structure of diverse cyclic molecules and their water complexes, together with the characterisation of the weak interactions that may be responsible for the conformational preferences of these molecules and complexes, by means of rotational spectroscopy and computational calculations.