Conjugated copolymers with novel low bandgap rhenium(I) complexes on the polymer main-chain are reported. The low bandgap metal-containing polymers were synthesized by Suzuki cross-coupling polycondensation or Stille coupling polymerization. The metal free copolymers are conjugatively-linked with functionalized intramolecular charge transfer units, which exhibited prominent absorption band in the UV vis region. These functionalized charge transfer units not only broadened the absorption spectrum, but also functioned as a bidentate ligand. Upon the complexation of rhenium(I) pentacarbonyl chloride, the absorption spectrum of the resulting polymers was further boardened, and the bandgap was reduced. The material design of this work has opened up a new approach in developing low bandgap metal-containing polymers as light harvesting materials.