Synthesis and characterization of linear luminescent Schiff-base polyelectrolytes with europium(III) in the backbone

The first luminescent linear europium(III) Schiff-base polyelectrolytes with europium in the polymer backbone have been synthesized and characterized. Europium-containing polyelectrolytes with ligand triplet states at or above the D-5(0) State of europium luminesce with high quantum yields, consistent with the intramolecular energy-transfer mechanism established for europium(III) complexes. New [NaY(tstm)](n) polyelectrolytes, where tstm(4-) is the anionic ligand derived from N,N ',N '',N<triple prime>- tetrasalicylidene-3,4,3 ',4 '-tetraaminodiphenylmethane, were synthesized with (M) over bar(n) values (up to 21 600) based on NMR end-group analysis. Intrinsic viscosities provide Mark-Houwink constants of a = 0.52 and K = 0.066 cm(3)/g for [NaY(tstm)](n). Mixed-metal [NaYxEu1-x(tstm)](n) polyelectrolytes provide enhanced emission over [NaEu(tstm)](n). The intensity is most enhanced for polyelectrolytes with Y:Eu ratios between 1:2.5 and 1:9, probably by intrachain energy transfer from the yttrium units of the polyelectrolytes to the Eu-III ions. [NaY0.2Eu0.8(tstm)](n) (Y:Eu = 1:4) luminesces more strongly than any other compound investigated and has a quantum yield of 0.74 at 77 K.