Bipyridinophane-fluorene conjugated copolymers have been synthesized via Suzuki and Heck coupling reactions from 5,8-dibromo-2,11-dithia[3]paracyclo[3](4,4')2,2'-bipyridinophane and suitable fluorene precursors. Poly[2,7-(9,9-dihexylfluorene)-co-alt-5,8-(2,11-dithia[3]paracyclo[3](4, 4')-2,2'-bipyridinophane)I (P7) exhibits large absorption and emission redshifts of 20 and 34 nm, respectively, with respect to its planar reference polymer Poly[2,7-(9,9-dihexylfluorene)-co-alt-1,4-(2,5-dimethylbenzene)] (P11), which bears the same polymer backbone as P7. These spectral shifts originate from intramolecular aromatic C-H/pi interactions, which are evidenced by ultraviolet-visible and H-1 NMR spectra as well as X-ray single-crystal structural analysis. However, the effect of the intramolecular aromatic C-H/pi interactions on the spectral shift in poly[9,9-dihexylfluorene-2,7-yleneethynylene-co-alt-5,8-(2,11-dithia[3]p aracyclo[3](4,4')-2,2'-bipyridinophane)] (P10) is much weaker. Most interestingly, the quenching behaviors of these two conjugated polymers are largely dependent on the polymer backbone. For example, the fluorescence of P7 is efficiently quenched by Cu2+, Co2+, Ni2+, Zn2+, Mn2+, and Ag+ ions. In contrast, only Cu2+, Co2+, and Ni2+ ions can partially quench the fluorescence of P10, but much less efficiently than the fluorescence of P7. The static Stern-Volmer quenching constants of Cu2+, Co2+, and Ni2+ ions toward P7 are of the order of 10(6) M-1, being 1300, 2500, and 37,300 times larger than those of P10, respectively. (c) 2006 Wiley Periodicals, Inc.