HALOGEN BONDING: A DFT AND VB INVESTIGATION

During my Ph.D. I focused my attention on the study of properties of the halogen bonding from a computational point of view. Due to the growing attention towards this kind of interaction, it is important to have some computational and theoretical models able to explain and reproduce its features. Halogen bonding, indeed, has been demonstrated to be a powerful tool due to the large number of applications in different fields, ranging from biological macromolecules to supramolecular chemistry (such as assemblies with nonlinear optical properties), from nanomaterials and crystal engineering (like the self-assembly control of host-guest solids, with applications in liquid-crystalline, porous, magnetic and organic phosphorescent materials) to materials science (such as the development of solid-state materials with peculiar electronic properties). Though a plethora of theoretical studies have been carried out on this interaction, there are still some open questions to be solved. I have investigated halogen bonding by using mainly two computational approaches, that is the Density Functional Theory (DFT) and the Valence Bond Spin-Coupled Theory. The first one is implemented in a number of widely used computational chemistry software programs, while the second one has been implemented by a restricted number of research groups, according to different strategies. In this thesis, after an introduction on the main properties of halogen bonding, I will briefly describe the Spin-Coupled Theory formulated on the Slater determinants, adopted for the present studies. The related software, developed by my supervisor Prof. M. Sironi, was able to treat up to 11 valence electrons. During my Ph.D. thesis, I worked in order to overcome this limitation: the software now runs on systems with up to 14 valence electrons. Finally, I will show the issues tackled and discuss the results obtained.