Solvent-induced terbium-emission in a fluorene-co-terpyridine metallopolymer

Abstract

This work reports the solvent effects on the photophysical properties of an alternated terbium containing copolymer, composed by fluorene and terpyridine units. The metallopolymer presents dual emission with bands at 390 nm (polymer main chain – blue emission) and 544 nm (main transition of the terbium ion – green emission). It was found that the terbium emission is sensitive to the chemical environment. Among all the solvents tested, luminescence was detected in DMSO only. The results strongly suggested that an aggregation-induced emission phenomenon (AIE) was operating in the lanthanide emission when DMSO was used. The phenomenon was accounted to the restriction of intramolecular motion (high polarity and viscosity effect) of the polymer main chain optimizing the antenna effect in the terbium complex. Theoretical studies involving the terpyridine units have also been carried out suggesting that DMSO environment may act stabilizing these structures in a cis–cis conformation, blocking non-radiative energy losses, optimizing the energy transfer to terbium ion.