To better understand and predict the properties of the π-conjugated compound especially in view of their use as organic solar cells, we have performed the investigation by using the DFT and TD-DFT quantum chemical calculations. The studied compounds are based on TTF- pyrazine , the aim is first to determine the geometries, electronic and optic properties by using the density functional theory (DFT/B3LYP) level with the correlationconsistent basis set 6-31G(d,p). Moreover, several physical parameters (HOMO, LUMO, Egap, Voc…..) were determined from the fully optimized structures. The absorption λabs is also calculated. This fundamental information is a valuable data in designing and making promising materials for organic solar cells.
