Preliminary studies on D-?-A Dyes for Dye-Sensitized Photocatalysis

Dye-sensitized photocatalysis (DSP) is a relatively new approach to convert sunlight into a fuel such as H2. The required optical and electrochemical properties of the dyes employed in DSP are very similar to those necessary for dye-sensitized solar cells (DSC), including: broad range of absorption in visible ?, high molar absorptivity, efficient electrons injection, stability on multiple red/ox cycles; as a result, the classes of compounds most commonly employed in DSP are those that have shown the highest efficiencies in DSC. Nevertheless, it's still not clear how the dye structure affects the efficiency of catalysis in H2 production experiments. Thus, the aim of this work is to try to find a reliable guideline for the synthesis of D-?-A dyes with optimized structures for hydrogen production using different Sacrificial Electron Donors (SED). There are only a few examples in the literature regarding this kind of compounds, only one of which contains the 2,1,3-benzothiadiazole moiety, a scaffold that has already shown impressive power conversion efficiencies in DSC. The preparation and spectroscopic/electrochemical characterization of some D-?-A small molecules containing the benzothiadiazole scaffold and featuring an extended conjugation and different electronic properties are reported. The compounds have been designed tuning the photophysical and chemical properties by a proper choice of terminal groups, ?-spacers ad side chains. All the dyes have been tested in DSSCs and in H2 production cells leading to interesting results in terms of production rate and TON.