We report in this article a DFT study of the bridging effect on structural and electronic properties of a several π- conjugatedsystems of thiophene and phenylene based on Cylopenta-ThienylenePhenylene (CPTP) co-oligomers in which both 3 and 2’positions (fig. 1a) were bridged with different fragment such as: CH2, SiH2, C(CN)2,S,C=O, C=S, C=CH2 and C=C(CN)2). The important reduction of the gap energy observed for the whole series of the bridged compounds studied here is explained on the basisof an orbital interaction analysis. The calculations methods were performed by using Gaussian09 program at density functional theory DFT/B3LYP level. The compounds bridged by C=S and C=C(CN)2 have small LUMO–HOMO gaps; leading to suggest them as the promising candidates for the optoelectronic device applications.
