Terbium Binding in Highly Luminescent Polymer Complexes

Polymer ligands containing a covalently bonded quinolinone fluorophore and COOH ( L1 ) or COONa ( L2 ) binding sites were synthesized by the reaction of high-molecular-weight poly[styrene- alt -(maleic anhydride)] with 7-amino-4-methylquinolin-2(1 H )-one and methanol and subsequent neutralization. The ligand-to-metal energy transfer and ligand binding properties in a series of [Tb(III)-ligand] complexes were investigated by steady-state and time-resolved luminescence spectroscopy in methanol or deuterated methanol. The intensity of the long-lived terbium(III) ion emission at 490, 545, 585 and 620 nm was greatly enhanced upon addition of L1 or L2 . Based on the differences in luminescence data obtained for [Tb(III)- L1 ] and [Tb(III)- L2 ] complexes, a qualitative model for the interaction of terbium(III) ion with L1 and L2 is put forward. The experimental luminescence decay curves were double-exponential (τ 1 , τ 2 ) with predominating longer component (rel B 1 > 85%) for both [Tb(III)- L1 ] and [Tb(III)- L2 ] complexes. About 2.5 or 2 methanol molecules were coordinated to Tb 3+ in [Tb(III)- L1 ] or [Tb(III)- L2 ] complexes, respectively, whereas ca. 6.5 methanol molecules were coordinated to Tb 3+ in methanol.