Studies on preparation, structure and fluorescence emission of polymer-rare earth complexes composed of aryl carboxylic acid-functionalized polystyrene and Tb(Ⅲ) ion

Abstract

4-(Chloromethyl) benzoic acid (CMBA) was first bonded onto the side chains of polystyrene (PS) via a polymer reaction, Friedel–Crafts alkylation reaction, and aryl carboxylic acid-functionalized polystyrene (PSBA) was generated. The functionalized polystyrene was used to prepare rare earth metal complexes. By using PSBA as macromolecule ligand, the binary polymer-rare earth complexes, PS-(BA)n-Tb(Ⅲ), were prepared, and at the same time, ternary polymer-rare earth complexes, PS-(BA)n-Tb(Ⅲ)-(Phen)m, i.e. the mixed complexes in which both polymer-based aryl carboxylic acid and 1,10-phenanthroline as ligands were also prepared. The complexes were fully characterized using FTIR and proton NMR spectroscopy. Both ultraviolet absorption and fluorescence emission spectra for the complexes were recorded. The relationship between complex structure and the intensity of fluorescence emission was established. The experimental results show that the fluorescence emission from the central metal ion in the complex is strongly sensitized by the aryl carboxylic acid ligands chemically attached to the side chains of PSBA, and an apparent “Antenna Effect” is produced for these complexes. In the dilute solution of PSBA, the formed complex belongs to intramolecular complex. For the binary intramolecular complex, the apparent saturated coordination number of Tb3+ ion is 10, and here the binary complex has the structure of PS-(BA)5-Tb(Ⅲ) and it has the strongest fluorescence emission among all of the binary complexes. When small-molecule Phen is added into the binary complex solution, the ternary complex PS-(BA)n-Tb(Ⅲ)-(Phen)m will be formed. As compared with the conventional ternary complexes PS-(BA)1-Tb(Ⅲ)-Phen2 and PS-(BA)1-Tb(Ⅲ)-(Phen)3 (the molar ratio of the central ion and the two ligands is conventional), the ternary complex with the structure of PS-(BA)5-Tb(Ⅲ)-(Phen)1 has the strongest fluorescence emission because of the complete coordination of the ligands to Tb3+ ion and the removal of the substituted water molecules around Tb3+ ion.