The wide collection of techniques available nowadays, which can be used to model the molecular behaviour and simulate the experiments, makes computational chemistry an essential partner of the experiment. In fact, the identification of correlations between chemical structures and molecular properties, on the one hand can suggest which kind of molecular systems to employ, due to their potential applications as new materials or drugs. On the other hand, can help to elucidate the origin of the experimental information, focussing onto the molecular features giving rise to the many detected observables. The computational approaches, which can be used to investigate the molecular properties, rely on quantum mechanical methods, such as ab initio, density functional theory (DFT), time dependent density functional theory (TD-DFT), and semi-empirical, or statistical methods such as Monte Carlo. Examples of molecular systems of interest are the inclusion complexes of organic compounds of pharmaceutical interest in cyclodextrins or micelles, the antimalarians such as Artemisinin, the compounds interesting for their potential application in organic light emitting diodes (OLED).