Efficient energy harvesting of conjugated polymers by direct coordination to novel low-energy complexes of europium

Abstract

Novel complexes based on a europium(III) core surrounded by three β-diketonate ligands were synthesized. The diketonates were synthesized by condensations of ethyl-2-pyrazinecarboxylate with various aromatic ketones. The metal centered emissions of the europium complexes as well as the ligand centered emission of the gadolinium complexes were studied. The complexes based on gadolinium were studied to establish the singlet and triplet energy levels of the ligands. These europium complexes were used to harvest energy from conjugated polymers. PPP-type polymers with bipyridine moieties and terpyridine pendant groups were studied initially. The europium complex attached to the bipyridine and terpyridine moieties facilitated energy transfer from polymer to europium. A novel class of polymers with a β-diketonate pendant group was synthesized and studied. Each of the polymers were synthesized via Suzuki coupling of 1,4-phenylbisboronic acid with a dibromoarenecarboxylate. Ethyl 3,5-dibromobenzoate was used in the polymerization to synthesize alternating copolymers of phenyl groups. These polymers were then reacted with 2-acetylthiophene to obtain polymers with β-diketonate pendant groups. The photophysics of these polymers and their lanthanide complexes were determined.