Interplay between chirality and dynamics of complex systems: a novel computational approach

The aim of this PhD project was to set-up a computational procedure for accurate and economic Electronic Circular Dichroism (ECD) calculations of complex systems, such as biomolecules or nanostructures. This goal was achieved combining classical molecular dynamics (MD) simulations, essential dynamics (ED) analysis, and state-of-the-art time-dependent density functional theory (TDDFT) calculations. The procedure was tested on several classes of systems, switching from small peptides in water to gold nanoclusters soluble in different solvent environments. By means of this protocol, we were able to extract the most probable conformers, explicitly include the solvent, and obtain a final statistically averaged ECD for each system under investigation. In all the cases, a good qualitative agreement between the experimental and calculated ECD spectra was obtained, thus confirming the reliability of the procedure. It is worth noting that, for the first time, conformational effects and explicit water molecules have been included in the ECD calculation of thiolate-protected gold nanoclusters. The method was also used to investigate the direct role of the aqueous solvent on chiroptical properties and vice versa, showing that the water itself can assume a chiral arrangement due to the solute-solvent interactions. Moreover, the scheme was employed to study the correlation between the conformational landscape in solution and the solid-state evolution of heterochiral Phe-based dipeptides. Therefore, this affordable, yet accurate, scheme for the computation of ECD spectra has shown its ability to reproduce different experimental situations, giving insight into the chiroptical properties of complex systems.