Investigations On Magnetic Function-directed Lanthanide-based Complexes

Currently, lanthanide-based single molecule magnets (SMMs) and moleculemagnetic refrigeration are the hotspots of the lanthanide-based molecule magnetism.In this dissertation, the main works have been carried out in the two aspects asfollowing:(1) Five isostructural clusters,[Ln24(DMC)36(μ4-CO3)18(μ3-H2O)2](Ln=Gd(1),Tb(2), Dy(3), Ho(4), Er(5)), have been synthesized by solvothermal method. They arenano-scale and capsule-like clusters. Magnetic measurements reveal that1possessesthe largest ΔSmvalue of46.12J·kg1·K1in all reported clusters, and3possesses theΔSmvalue of13.8J·kg1·K1and single-molecule magnet behaviour with the energybarrier of72.84K (50.9cm1) and pre-exponential factor of1.92×109s. Otherwise,the other clusters do not exhibit frequency dependences.(2) Na@Cu24Gd6(6) and Na@Cu24Dy6(7), and Na@Cu12Gd6(8) clusters havebeen synthesized by using L-alanine and chloroacetic acid, respectively. Magneticentropy changes of6and8is21.2and28.1J·kg1·K1, respectively. Cluster7showsslow magnetic relaxation behavior with energy barrier ΔE/kBof34.0K (23.8cm1)and pre-exponential factor of τ0=8.16×107s.(3) Two isostructural clusters DyZn6(9) and ErZn6(10) have been synthesizedby employing amine acetic acid. Alternating-current (ac) magnetic susceptibilitiesmeasurements reveal that cluster9exhibits single molecule magnet behavior withenergy barrier ΔE/kBof37.0K (25.9cm1) and pre-exponential factor of τ0=8.16×107s. Otherwise, cluster10dose not exhibit frequency dependences.(4) Two simple three dimensional coordination polymers [Gd(HCO2)3]n(11) and[Gd(OH)(CO3)]n(12) have been synthesized and structural charactered by X-raysingle-diffraction. They can be obtained by simple synthesized with high yields andexhibit high thermal and chemical stabilities, especially ultra-strong alkali resistance.The investigations on magnetocaloric effect (MCE) of11and12reveal that the massand volumetric magnetic entropy change Smof11is53.8J·kg1·K1and208mJ·cm3·K1(ΔH=7T), respectively. And the mass and volumetric magnetic entropychange Smof12is63.2J·kg1·K1and340mJ·cm3·K1(ΔH=7T), both of whichare the largest values among those of reported molecule magnetic cryogenic materials.(5) Utilizing isonicotine as ligand, four three dimensional coordination polymersLn3Cu12I12(Ln=Gd(13), Dy(14)) and Ln4Cu4I3(Ln=Gd(15), Dy(16)) have beenprepared via solvothermal method. The investigations on MCE reveal that the mass magnetic entropy change Smis10.4J·kg1·K1for13and20.3J·kg1·K1for15(ΔH=7T), respectively. Ac magnetic susceptibilities reveal that16exhibits singlemolecule magnet behavior with energy barrier ΔE/kBof2.4K (1.68cm1) obtained byfitting using Debye mode, Otherwise,14does not exhibit frequency dependences.(6) Two2D coordination polymers Ln8Mn3(Ln=Gd(17), Dy(18)) and two3Dcoordination polymers Ln2Mn (Ln=Gd(19), Dy(20)) have been synthesized viaemploying isonicotine as ligand. The investigations on MCE reveal that the massmagnetic entropy change Smis42.0J·kg1·K1for17and31.5J·kg1·K1for19(ΔH=7T), respectively. Ac magnetic susceptibilities reveal that18and20exhibitfrequency dependences.