DFT/B3LYP study of bridging e ffect on structural and electronic properties of a short π-conjugated systems based on thiophene and phenylene

We report in this article a DFT study of the bridgi ng effect on structural and electronic properties o f a several πconjugatedsystems of thiophene and phenylene based on Cylopenta-ThienylenePhenylene (CPTP) co-oligomer s in which both 3 and 2’positions (fig. 1a) were bridged with different fragment such as: CH 2, SiH 2, C(CN) 2,S,C=O, C=S, C=CH 2 and C=C(CN) 2). The important reduction of the gap energy observ ed for the whole series of the bridged compounds studied here is explained on the basisof an orbital interaction analysis. The calcul ations 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.