Effects of bridging groups on electronic structures of conjugated cyclic polymers

Summary form only given. Theoretical investigation was performed to elucidate effects of the bridging groups on the band gaps of conjugated cyclic polymers. In addition to poly(para-phenylene) and heterocyclic polymers such as polythiophene, polypyrrole, and polyfuran, the polymers concerned in this study include the conjugated cyclic polymers which contain bridging groups of an XY/sub 2/ form (CH/sub 2/, CF/sub 2/, SiH/sub 2/ and SiF/sub 2/) or an X=Y form (C=CH/sub 2/, C=O and C=S). Geometrical structures of the polymers were optimized through semiempirical band calculations with AM1 Hamiltonians. A modified extended Huckel method was employed to obtain electronic structures of the polymers. Effects of the bridging groups on band gaps of the polymers were analyzed in terms of geometrical relaxations and electronic perturbations.