Construction and properties of a light-harvesting antenna system for phosphorescent materials based on oligofluorene-tethered Pt–porphyrins

Abstract

Tetramerous molecular assemblies composed of four oligofluorenes as a light-harvesting antenna (LHA) and a Pt–porphyrin core as a phosphorescent chromophore were designed and synthesized for obtaining efficient phosphorescent materials. The resulting molecules showed good solubility in common organic solvents and high film-formability. From the series of optical measurements, it was shown that bright phosphorescence was observed from the LHA molecules. Efficient energy transfer through the cardo structure was confirmed from the oligofluorene units to the Pt–porphyrin core. Additionally, it was shown that aggregation-caused quenching (ACQ) and oxygen-deactivation of phosphorescence can be inhibited in the film state because of steric hinderance of bulky rings on the cardo structure. Finally, film materials with oxygen-resistant solid-state phosphorescence were obtained. Our material design is feasible not only for constructing highly-emissive solid-state phosphorescent materials but also for enhancing environment resistance to emissive materials by a unique structural unit.