Synthesis And Luminescent Properties Study Of Metal-organic Polymers Based On Pyridine-benzimidazole Tridentate Rare Earth Complexes

In recent years,significant progress has been made in the field of metal-organic polymers.Many metal-organic polymers exhibit excellent chemical stability,thermal stability,and optical properties,making them potentially valuable in applications such as optoelectronic devices,catalysts,sensors,and energy storage.Despite the broad prospects of metal-organic polymers in the field of materials science,they still face challenges and issues such as complex synthesis methods,poor stability in air or humid environments,and the need for further optimization and control to meet the specific requirements of various application areas.In this study,we addressed the complexity of synthesis methods and material stability by designing and synthesizing novel ligands.These ligands were then assembled with rare-earth metal ions to form rare-earth nitrate complex[REL（NO₃）₃]and chloride complex[RELCl₃].Subsequently,the two series of rare-earth complexes were used as monomers to copolymerize with methyl methacrylate（MMA）and styrene（STY）,resulting in four series of metal-organic polymers:Poly（MMA-co-[REL（NO₃）₃]）,Poly（MMA-co-[RELCl₃]）,Poly（STY-co-[REL（NO₃）₃]）and Poly（STY-co-[RELCl₃]）.The structures of these polymers were characterized using nuclear magnetic resonance,infrared spectroscopy,and elemental analysis.Their photophysical properties,including UV-visible absorption and fluorescence spectra,were also investigated.The results showed that complex[REL（NO₃）₃]sensitized the emission of Eu（III）,Tb（III）,Sm（III）,and Dy（III）,while complex[RELCl₃]only sensitized Eu（III）and Tb（III）emission.Furthermore,the same RE（III）ion exhibited better luminescent behavior in[REL（NO₃）₃]compared to[RELCl₃].After polymerization,the polymers with the same RE（III）ion demonstrated higher luminescence intensity,quantum yield,and photostability compared to the corresponding complexes.The chloride polymers showed luminescence sensitization of Sm（III）and Dy（III）.Eu（III）and Tb（III）ions were found to be the most efficient sensitizers among the rare-earth ions,with the polymer containing Eu（III）exhibiting stronger and more stable luminescence than the polymer containing Tb（III）.By adjusting the feed ratios,three different ratios of mixed rare-earth metal-organic polymer luminescent materials containing Eu（III）and Tb（III）were obtained,showing that the concentration of RE（III）has a certain influence on the luminescence of the polymers.Additionally,by copolymerizing the monomers of Eu（III）and Tb（III）complexes with MMA or styrene,color-tunable mixed rare-earth metal-organic polymer luminescent materials were achieved.