Geometry optimization calculations for 5, 5¯-((Pentane-2,4-Diylidene bis (-1-yl-1Yalideneazan)) bis (1,3,4- Thiadazole-2-thiol), B, is carried out to establish a direct correspondence between experimental and theoretical by using density functional theory (DFT) with B3LYP/6-31G. The theoretical IR and 1H-NMR for the same molecule are performed at the same level of theory. These data suggest that the spectra of the thiadazole are consistent with the thiadazole architecture proposed by Athraa and co-workers. The investigation of HOMO and LUMO approved that this molecule is very suitable to be a semiconductor material because it has a very low energy band gap equal to 0.13628 eV.