Preparation and Photoluminescence Properties of Polymer-Rare-Earth Complexes Composed of Bidentate Schiff-Base-Ligand-Functionalized Polysulfone and Eu(III) Ion

A bidentate Schiff-base (SB) ligand was synthesized and bonded on the side chains of polysulfone (PSF) through several polymer reactions by molecular design, and the bidentate Schiff-base-ligand-functionalized PSF, PSF-SB, was obtained. On this basis, new types of polymerrare-earth complexes, namely, binary complex PSF-(SB)(3)-Eu(III) and ternary complex PSF-(SB)(3)-Eu(III)-(Phen)1, were prepared through the coordination reactions between PSF-SB as a macromolecular ligand, 1,10-phenanthroline (Phen) as a second small-molecule ligand, and Eu(III) ion. The functional polymer PSF-SB was fully characterized by FTIR, H-1 NMR, and chemical analysis methods, and the complexes were also fully characterized by FTIR and UV absorption spectroscopies. The fluorescence emission characteristics and luminescence mechanism of the complexes were investigated in depth. The experimental results show that the macromolecular ligand PSF-SB itself emits strong fluorescence centered at 415 nm. However, after coordination to Eu(III) ion, the fluorescence emission of PSF-SB weakens markedly, and this behavior should be attributed to intramolecular energy transfer. Both the binary and ternary complexes exhibit the strong characteristic fluorescence emission of the Eu(III) ion. This fact demonstrates that the bidentate Schiff-base ligand SB bonded on the side chains of PSF can effectively produce intramolecular energy transfer, that is, it can strongly sensitize the fluorescence emission of the Eu(III) ion, indicating that the triplet-state energy of the bonded ligand SB is well matched with the resonant energy level of the Eu(III) ion. The fluorescence emission intensity of the ternary complex PSF-(SB)3-Eu(III)-(Phen)1 is stronger than that of the binary complex PSF-(SB)3-Eu(III), and this result is associated with the synergistic coordination of the second ligand Phen with the bond ligand SB, as well as its ability to substitute the coordinated water molecules around the Eu(III) ion.