Syntheses,Structures And Magnetic Properties Of Lanthanide Complexes Based On 8-hydroxyquinoline Schiff Base

Currently,the study of lanthanide-based single molecule magnets(SMMs)has become one of the research hotspots of the molecule magnetism.In this dissertation,thirty-six new lanthanide complexes have been synthesized,structurally and magnetically characterized driven by the research hotspots of the single molecule magnets(SMMs),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 paper as following:1.Sixteen lanthanide(III)dinuclear complexes based on three8-hydroxyquinoline Schiff base ligands(HL1,HL2 and HL3)have been synthesized by using solvent evaporation method.These complexes were characterized by the single crystal X-ray diffraction,elemental analysis(EA),powder X-ray diffraction(PXRD),TG investigated,and further studied them by using luminescent spectra and magnetic measurements.The magnetic study reveals that 1 and 6 display cryogenic magnetic refrigeration properties,whereas complexes 3,7,8 and 10-16 show different SMMs behaviors with energy barriers(Ueff /kB)of 6.77 K for 3,10.39 K for 7,19.83 K for 8,25.65 K for 10,22.04 K for 11,79.1 K for 12,29.4 K for 13,43.5 K for 14,13.7 K for 15 and 54.8 K for 16.Our work demonstrates that the SMM behavior of lanthanide complexes can be finely adjusted by changing the substituent of the?-diketonate ligand.2.While complexes 12 and 15 have very similar structures,magnetic studies reveal that they exhibit different magnetic relaxation behaviors: double magnetic relaxation processes were observed in 12,but single magnetic relaxation process was observed in 15.The distinctive magnetic relaxation behaviours of 12 and 15 mostly originated from different halogen substitution in preparing them.3.Two series of dinuclear lanthanide(III)complexes based on two different alkoxy substitution of 8-hydroxyquinoline Schiff base ligands(HL4 and HL5)have been synthesized,structurally and magnetically characterized.Magnetic measurements reveal that 19,23,26 and 27 exhibit SMMs behavior with energy barrier(Ueff /kB)of 34.5 K for 19,67.6 K for 23,1.73 K for 26 and 31.2 K for 27.The dissimilar dynamic magnetic behavior of 19 and 23 are mostly result from different electron-donating effect induced by the two alkoxy(-OCH3 and –OC2H5)of the8-hydroxyquinoline Schiff base ligands.4.Using three 8-hydroxyquinoline Schiff base derivatives(H2L6,HL7 and HL8)designed and synthesized lanthanide-based single molecule magnets(SMMs),nine lanthanide(III)complexes have been successfully obtained by solvent evaporation method.Magnetic measurements indicated that 28,29,31,33 and 36 exhibit different magnetic relaxation behaviors.According the Arrhenius law: ? = ?0exp(Ueff/kBT),the best fitting results give the energy barriers(Ueff/kBT)of 73.68 K for 33 and the pre-exponential factors ?0 of 3.9×10-9 s,Otherwise,32 and 34 do not exhibit frequency dependences.