Synthesis, optical characterization and computational study of novel organic fluorophores

Over the last three decades lot of interest has been devoted to light harvesting technologies. Recent findings on global warming and energy nonrenewable resources push us to alternative means of storing energy. Sunlight stands indeed as an ideal asset to take advantage of. In this insight Luminescent Solar Concentrators (LSCs) represent a way to decrease the cost of solar photovoltaics. LSC devices usually consist in a thin slab of transparent material (glass or polymer) doped with a fluorescent dye. Upon solar irradiation, a fraction of the emitted light, through means of internal reflection, is collected at the edges of the device where photovoltaic cells are located. Compared to traditional concentrators, which make use of mirrors and lenses, these devices show numerous advantages, such as theoretical higher concentration factors, the ability to work with both diffuse and incident light and no need for tracking devices or cooling apparatuses. Organic fluorescent dyes bearing π-conjugated electron-donor and -acceptor moieties exhibit intramolecular charge-transfer (ICT) properties, and can therefore show the optical properties required by LSCs such as high quantum yield and high Stokes shift. On account of this, the present dissertation will discuss the synthesis, UV-Vis characterization and computational study of a set of novel unsymmetrical and symmetrical push-pull azole-based dyes. These compounds are characterized by a 1,3-azole 2,5 substituted with two aromatic moieties bearing electron withdrawing (EWG) or electron donating (EDG) groups. Remarkably, the introduction of an heteroaromatic ring usually improves the thermal and chemical stability and the overall polarizability of the fluorophore. The studied compounds were prepared through a robust synthetic pathway involving a palladium and copper-promoted direct C-H arylation reaction as key step. We took into account the effect of the peripheral electron poor funtionality as well as the nature of the central heteroaromatic core. In order to rationalize the experimental results we carried out TD-DFT studies, that allowed us to proper understand the charge tranfer occuring during the electronic transition. After selecting the best fluorophores for our aim, we investigated its efficiency in an LSC prototypes.