Investigation On Multivariant And Multinuclear Rare-Earth Complexes Based Luminescence/Magnetic Function:Syntheses,Structures,and Properties

Rare-earth complexes have received considerable attention because of their employment in fluorescence,magnetism,gas separation,catalysis,and adsorption aspects in the past few decades.Thus far,a multitude of complexes mainly around single-molecule magnets?SMMs?and molecular coolers with magnetocaloric effect?MCE?have been reported.In this thesis,seventeen new Rare-earth?RE?complexes have been synthesized based on 8-hydroxyquinoline Schiff base by modulating?-diketonate derivatives.Especially,the structures and luminescence/magnetic properties of complexes,as well as the relationship of the structures and magnetic properties of SMMs have been deeply explored.The main works have been carried out in this thesis as following:1.Two series of new tetranuclear clusters,[RE₄?dbm?₄?L1?₆??₃-OH?₂]·[solvents]?RE=Y?1?,Gd?2?,Tb?3?,Dy?4?,Ho?5?,Er?6?and Lu?7??and[RE₄?acac?₄?L1?₆??₃-OH?₂]·[solvents]?RE=Gd?8?,Tb?9?and Dy?10??,based on dibenzoylmethane?Hdbm?,acetylacetonate?Hacac?and 8-hydroxyquinoline Schiff base ligand?HL1?have been synthesized.These complexes were characterized by the single crystal X-ray diffraction,elemental analysis,powder X-ray diffraction,thermogravimetric analysis investigated,and further studied the luminescent spectra and magnetic property.2.X-ray diffraction data reveals that 1-7 are isomorphous and crystallize in the triclinic space group P?;while 8-10 exhibit similar tetranuclear structure and crystallize in the monoclinic space group P2₁/c.In the centrosymmetric unit,four RE???ions locate at the corners of a parallelogram,each 8-coordinated RE???ion suits in a distorted square-antiprismatic geometry.Magnetic studies showed that 2 and8 act as cryogenic magnetic refrigerants with the-?S_m=17.77 and 22.11 J kg^-11 K^-11 at2 K for?H=7 T,respectively.The Dy₄ clusters exhibit different slow magnetic relaxation processes under zero dc field,it's noted that 10 displays two relaxation phases corresponding to the high-frequency peaks?fast relaxation phase,FR?and the low-frequency peaks?slow relaxation phase,SR?.With the optimized dc fields for 4and 10,the quantum tunneling of magnetization?QTM?was suppressed with the effective energy barriers as high as 109.48 and 116.20 K,respectively.In addition,the luminescence properties of 3 and 9 show the characteristic emissions of Tb^?ion,while the fluorescence spectra of 1 and 7 bear similarity to that of the HL1.The relationship of the structures and magnetic properties for 4 and 10 illustrates that RE₄clusters display subtle variation in single crystal structure by changing the substituent groups of?-diketonate derivatives,but display remarkably different magnetic behaviors;thus further illustrate that the lanthanide single molecule magnets are closely related to the coordination environment of Ln^?ion.3.Sevenphenoxo-O-bridgedbinuclearlanthanidecomplexes[Dy₂?acac?₂?L2?₂?CH₃OH?₂]·CH₃OH·3H₂O?11?,[Ln₂?acac?₂?L2?₂?H₂O?₂]?Ln=Tb?12?,Ho?13?,Er?14??,[Eu₂?dbm?₂?L2?₂?C₂H₅OH?₂]?15?,and[Ln₂?dbm?₂?L2?₂?DMF?₂]·CH₂Cl₂?Ln=Eu?16?,Ho?17??,basedon8-hydroxyquinoline Schiff base?HL2?and?-diketonate derivatives have been constructed and characterized.4.X-ray diffraction analysis reveals that 11-17 are binuclear complexes and 11crystallizes in trigonal R-3 space group,12-15 crystallize in the monoclinic C2/c space group,16-17 are isomorphic and crystallize in the triclinic P?space group.In each structure unit,8-coordinated Ln^?ion is suited in the triangular dodecahedron except that 15 adopts a square-antiprismatic geometry.The luminescence properties of 11,12 and 15/16 show the Dy^?,Tb^?and Eu^?ions characteristic emissions.The alternating-current?ac?susceptibility of 11 showed that Dy₂ exhibits SMMs behavior and the imaginary part does not appear complete peaks with the QTM under zero dc field.