`
The band gap of vinylene-linked seven membered organic heterocyclic conducting polymers 1 to 4, are calculated by implementing DFT with B3LYP/6-31G(d,p) method. The effect of chemical modification by introducing heteroatom on the electronic structure of polymers is discussion. The fact that introducing a heteroatom increases conjugation, chemical stability and affects the band gap of the aromatic ring is also discussed. It is concluded that vinylene-linked, azepine based polymer 2 has the lowest band-gap among all the investigated systems and hence has a better conducting properties. Our results highlight the use of computation for designing materials with enhanced photovoltaic applications.