Synthesis And Propeities Of Rare Earth Complexes With Highly Magnetic Anistropy

With the development of the information age,people have higher requirements for information storage capacity and information storage equipment is developing torwards miniaturization,high speed and large capacity.Because of their potentials in high-density information storage,spin quantum devices,and qubits,single-ion magnets have become a research hotspot in the fileds of physics,chemistry and materials.In addition,rare earth ions can emit strong sharp-line spectra in the ultraviolet to near-infrared region,and can construct rare earth complexes for luminescence sensing.In this paper,eight rare earth complexes with novel structures have been synthesized using phosphine oxide ligands and carboxylic acid ligands.The contents are as follows:In the first part,two dysprosium single-ion magnets with pentagonal biconical configurationweresynthesizedusingHMPAastheligand:[Dy（HMPA）2（H2O）5]2Br6·2HMPA·2H2O（1）and[Dy（HMPA）2（H2O）5]2Cl6·2HMPA·2H2O（2）.X-ray single crystal diffraction results show that the two complexes are isostructural;magnetic studies show that 1 and 2 are single ion magnets,and their effective thermal barrier are 556 K and 477 K,respectively,and their blocking temperatures are 12 K and 8 K,respectively;In addition,we analyzed the quantum tunneling behavior in 1 and found that the external magnetic field and diamagnetic dilution can effectively suppress the quantum tunneling effect.Further analysis of the magnetic configuration relationships shows that the counterion has a greater influence on the magnetic behavior,exceeding the influence of changing the substituent of the phosphine oxide ligand.In the second part,two pentagonal bipyramid holmium single ion magnets were synthesized using HMPA as the ligand:[Ho（HMPA）2（H2O）5]2Cl6·2HMPA·2H2O（3）and[Ho（HMPA）2（H2O）5]Br3·2HMPA（4）.3 and 4 have the same[Ho（HMPA）2（H2O）5]³⁺unit and different counter ions;magnetic studies have shown that the highly symmetrical crystal field effectively suppresses the quantum tunneling effect of the Ho³⁺ground state,so that 3 and 4are single-ion magnets under zero field,and the effective thermal barrier are 290 K and 320 K respectively.The study of the magnetic configuration relationships found that the second coordination layer has a certain influence on the magnetic properties of the single ion magnet.In the third part,a new ligand H2btdc was synthesized and characterized.Four isostructural three-dimensional rare earth organic framework complexes were synthesized by H2btdc:[Ln2（btdc）3·DMF·2H2O]2DMF·4H2O（Ln=Dy（5）,Tb（6）,Gd（7）,Eu（8））.The magnetic properties of 5 and 7 were studied,and it was found that there is a great quantum tunneling effect in 5;Fluorescence performance studies have found that 8 can emit Eu³⁺characteristic red light,and can specifically detect Fe³⁺,with a detection limit of 3.45×10^-6 mol·L^-1.The detection mechanism research shows that the fluorescence quenching of 8 by Fe³⁺is caused by the interaction between Fe³⁺and S,O in the ligand and the energy competition absorption.