Tuning the electronic properties of conjugated polymer by tethering low-bandgap rhenium(I) complex on the main chain

Abstract

Low-bandgap rhenium(I) complex with absorption onset at 795 nm in solution was tethered onto π-conjugated polymer. The conjugated copolymer provides solution processability of the metallopolymer, and the pendant allows the low energy-absorbing Re(I) complex units to be evenly distributed on the thin film. The copolymer tethered with low-bandgap rhenium complex was synthesized by Suzuki cross-coupling reaction. The metal-free polymer (poly-1) tethered with functionalized intramolecular charge transfer dye, 2-phenyl-3-pyridin-2-yl-5,7- di-2-thienylthieno[3,4-b]pyrazine, exhibited high molecular weight, good film-forming properties, and excellent solution processability. The pendants of the conjugated polymer possess donor-acceptor characters and broaden the absorption band. These pendants can function as bidentate ligands for metal chelation. The solubilizing groups on the monomers provide good solubility to the polymer even with high content of metal chelation. Upon the complexation with rhenium(I) pentacarbonyl chloride, the absorption spectrum of the resulting metallopolymer was further extended toward the near-infrared region. Photovoltaic performances based on this metallopolymer have been studied. The design approach of these metallopolymers provides synthetic feasibility for coordinating wide range of metal ions on the pendant, and the resulting low-bandgap polymer can be a potential candidate for light harvesting material in solar cell applications. © 2010 Wiley Periodicals, Inc.