Study On Synthesis And Properties Of Rare Earth Functional Complexes Based On Multidentate Ligands

Based on the excellent characteristics of narrow-band emission,long luminescence lifetime,large Stokes shift,and high quantum yield of rare earth ions,rare earth coordination polymers have excellent properties in terms of luminescence,electricity,and magnetism.Luminescent rare-earth coordination polymers are often used in various aspects such as white light emission,bio-imaging,anti-counterfeiting,anion,cation detection and small molecule detection.The complex can be doped or grafted to obtain a composite luminescent material.On the one hand,using the salicylamide group as the terminal group of the rare earth complex can not only effectively sensitize the luminescence of rare earth ions,but also can generate a larger steric hindrance when the ligand is coordinated with the rare earth ion,reducing the non-radiative transition caused by solvent coordination,making the rare earth ions highly selective for ligands and can further obtain a rare earth complex with better luminescence properties.On the other hand,doping the light-emitting substance into the organic matrix can minimize the self-quenching emission of the high-concentration solid-state light emitter,thereby increasing the emission intensity.Multidentate salicylamide ligands are very suitable for the construction of rare earth coordination polymers with excellent light-emitting properties due to their semi-rigid structure and suitable energy levels.With functional orientation as the target and structural research as the means,this paper uses 4-methylpyridine as the central skeleton to design and synthesize two new salicylamide poly-monodentate ligands and their rare earth coordination polymers,the structure and luminescence performance of the system are studied systematically.Based on the poor water resistance of the salicylamide rare earth complexes and for the purpose of expanding their luminescence applications,a polymethyl methacrylate(PMMA)matrix was introduced to obtain luminescent hybrid films.The luminescence properties,stability and response to luminescence of the hybrid films were explored systematically.The main content of this paper is divided into the following four parts:1.The research status of luminescent rare earth complexes and the topic and significance of the paper were reviewed.2.With 2-(hydroxymethyl)-2-(pyridin-4-yl)propane-1,3-diol as the starting reactant,2-methylpyridine used as the central skeleton and the terminal groups,new poly-monodentate ligands L? and L? of salicylamide methylthiophene and salicylbenzylamine,where LI=2,2'-((2-(pyridin-4-yl)-2-((2-(((thiophen-2-ylmethyl)aminomethoxy))Phenoxy)methyl)propan-1,3-diyl)bis(oxy)bis(N-(thien-2-ylmethyl)benzamide)))),L?=2,2'-((2-((2-(benzylcarbamoyl)phenoxy)methyl)-2-(pyridin-4-yl)propan-1,3-diyl)bis(oxy)bis(N-benzyl Benzamide)),were developed together with their rare earth complexes which were characterized by infrared spectra,thermogravimetric analysis,and X-ray diffraction.The structural analysis shows that series of rare earth coordination polymers are all planar network structures,in which the ligand acts as a tri-monodentate ligand to bridge the rare earth ion,and the uncoordinated salicylamide side chain connects the planar network structure expands into a three-dimensional supramolecular system.3.The luminescence properties of a series of complexes were studied:both ligands are excellent sensitizing ligands for Tb3+,and only partially sensitized to Eu3+,so the former shows bright yellow-green light of Tb3+,while the latter shows pink emission.For the purpose of expanding the luminescence applications of such complexes,we dispersed a series of Eu3+ and Tb3+coordination polymers in a polymethyl methacrylate matrix to obtain a series of rare earth composite film materials.Studies on their luminescence properties and stability show that the water and thermal stability of the films are higher than the corresponding rare earth complexes.The research on the luminescence properties of composite thin films shows that the luminescence properties of the hybrid films are not only better than the pristine compound,but also show the ratiomtric luminescence response to Zn2+ in aqueous system.4.Results and Prospects:This paper reports the synthesis,structure,and luminescence properties of a series of new light-emitting rare earth complexes and their hybrid films,and discusses the relationship between structure and performance.The results presented herein has important theoretical significance and potential application value for the design and synthesis of luminescent rare earth complexes with excellent properties.