Molecular Magnetic And Magnetic Refrigeration Properties Of Polynuclear Rare Earth Complexes

Due to the potential applications of rare earth single-molecule magnets（SMMs）in high-density information storage and molecular spintronics,similar research has been highly sought after by researchers in recent years.At the same time,the research of multifunctional molecular magnets including magnetic refrigeration and fluorescence has attracted extensive attention.Although the research of SMMs has made rapid progress,the field still faces many thorny problems such as low blocking temperature and serious quantum tunneling of the magnetization.In view of the urgent scientific problems in this field,four polynuclear lanthanide complexes were constructed using salicylaldehyde and its derivatives with lanthanide acetate salts.Five binuclear complexes and two mononuclear complexes were synthesized by using different phosphine oxides as bridging ligands andβ-diketone metal salts.The magnetic properties of the complexes were studied,and the results showed that the complexes exhibited significant single-molecule magnetic behavior and magnetocaloric effect.The main work is as follows:1.Four polynuclear rare earth complexes were synthesized from 2-hydroxy-3-methoxybenzaldehyde and o-phenylenediamine condensed 2,3-dihydroxybenzaldehy de with lanthanide acetate salts:[Gd₄₂（L~1）₁₄（OH）₂₈（OAc）₈₄]（1）,[Dy₄₂（L~1）₁₄（OH）₂₈（OAc）₈₄]（2）,Gd₄（L~2）₄（OAc）₂（OH）₂（3）,[Dy₄（L~2）₄（OAc）₂Cl（OH）]（4）（L~1=2-hydr oxy-3-methoxybenzaldehyde,L~2=o-phenylenediamine condensed 2,3-dihydroxybe nzaldehyde）.The magnetic properties of complexes 1-4 were characterized,and t he results showed that complexes 1 and 3 had higher magnetic entropy changes.It is worth mentioning that complex 4 exhibits remarkable slow magnetic relaxati on behavior accompanied by a hysteresis loop similar to that of ferromagnetic,a nd the QTM is also effectively suppressed.2.Five binuclear lanthanide complexes and two mononuclear lanthanide com plexes were synthesized by using phosphine oxide as bridging ligand andβ-diket one lanthanide metal salt:[Dy₂（dppe O₂）（acac）₆（OH）₂]（5）,[Gd₂（dppe O₂）（acac）₆（OH）₂]（6）,[Eu₂（dppe O₂）（acac）₆（OH）₂]（7）,[Tb₂（dppe O₂）（acac）₆（OH）₂]（8）,[Dy₂（dppe O₂）（acac）₆（OH）₂]（9）,[Dy₂（TPPO）（TMHD）₆]（10）,[Dy₂（Cy₃PO）（TMHD）₆]（11）（acac=acetylacetone,TMHD=2,2,6,6-tetramethyl-3,5-heptanedione,dppe O₂=1,2-bis（diphenylphosphine oxide）ethane,TPPO=triphenylphosphine oxide,Cy₃PO=tric yclohexylphosphine oxide）.The magnetic properties and fluorescence spectra of metal characteristic peaks of complexes 5-11 were analyzed.Complexes 5,6,9,10 and 11 exhibited typical single-molecule magnetic behavior,and both 7 and 8exhibited characteristic fluorescence emission peaks of lanthanide ions center.