Syntheses,Structures And Magnetic Properties Of High-Nuelearity Lanthanide And Lanthanide-Transition Metal Clusters

Molecular magnetic materials have received much attention in the past two decades,especially high-nuclearity lanthanide-containing clusters,not only because of their charming structures but also because of their abundant optic,electric,magnetic and catalytic properties,such as the interesting magnetic properties caused by the unique electronic exchange between metal ions.However,the formation of high-nuclearity lanthanide-containing clusters is extremely complicated and it is still a challenge to explore the formation mechanism and reasonably design and synthesize the high-nuclearity lanthanide-containig clusters.In this dissertation,around the title"Syntheses,Structures and Magnetic Properties of High-nuclearity Lanthanide and Lanthanide-Transition Metal Clusters",small sterically hindered carboxylic acid as ligands with the anion template method have resulted in series of high-nuclearity lanthanide clusters and high-nuclearity lanthanide-transition metal clusters.And the synthetic strategies,assembly rules and magnetic properties of the high-nuclearity lanthanide-containing clusters are investigated.The detail findings are following:1.Syntheses,Structures and Magnetic Properties of High-nuclearity Lanthanide Metal Clusters Based on Carboxylate Ligands.1)Firstly,a series of low-nuclearity lanthanide metal clusters Nd2,Dy4 and Gd6 were obtained by controlling the hydrolysis of lanthanide ions using a simple carboxylic acid Betaine as ligand and introducing lanthanide ions with different radii.When Cl-and NO3-were introduced as mixed anion templates,two double-cage high-nuclearity lanthanide metal clusters Nd34 and Eu34 were obtained.2)Then,the OD lanthanide metal clusters Dyi9 and Tb19 were prepared by using multi-dentate chelate ligands to control the hydrolysis of lanthanide ions.1D chain and 3D framework complexes Lni9-1D and Lni9-3D(Ln=Dy3+/Tb3+)were obtained through changing the steric hindrance of the ligands.3)Finally,two cage-like high-nuclearity lanthanide clusters Gd27 and Dy27 were obtained by using propionate with small sterically hindered as ligand and introducing CO32-and ClO4-as mixed anion templates.Magnetic studies indicated that compound Gd27 displays a large magnetocaloric effect and compound Dy27 shows a significant frequency dependence.2.Syntheses,Structures and Magnetic Properties of High-nuclearity Lanthanide Metal Clusters Based on Acetate and Polyol Mixed Ligands.1)Firstly,when N-acetyl-D-glucosamine(GlcNAc)was used as an ancillary ligand,the lanthanide ions highly selecative and coordinate with Chromogen I,which is one of the in-situ decomposition products of GlcNAc,in the form of lanthanide metal clusters Gd9 and Dy9.High-resolution mass spectrometry demonstrated the stability of compounds Gd9 and Dyg in solution.2)When trithanolamine was selected as the auxiliary ligand and multiple ClO4-were introduced as the multi-anion templates,a gigantic cage-like lanthanide cluster Gd104 was obtained.Magnetic studies shown that it has a large magnetic entropy change at the low temperature and high field.3)When the myo-Inositol containg more hydroxyl groups is selected as ancillary ligand,the gigantic wheel-like lanthanide cluster Gd140 was prepared with the slowly forming CO32-as multi-anion templates by fixing CO2 from atmosphere,which is the largest lanthanide cluster with the highest nuclear number and the larges size to date.It can be observed clearly by scanning transmission electron microscope(STEM),which futher confirm the stability of compound Gd140.3.Syntheses,Structures and Magnetic Properties of High-nuclearity Lanthanide-Transition Metal Clusters Based on Carboxylate Ligands.1)Firstly,acetate was selected as ligand with different lanthanide ions coorperatively control the hydrolysis of Fe3+ ions,the high-nuclearity lanthanide-iron metal clusters Ln6Fei3(Ln＝La3+/Gd3+/Dy3+)were obtained with the centered a-Keggin {Fe13} anion protected by lanthanide ions.Compared to compound La6Fe13,the anisotropy of the entire cluster Gd6Fe13 decrease obviously due to the introduction of isotropic Gd3+ ions.2)Two nanosized high-nuclearity lanthanide-transition metal clusters Gd24Zn4 and Sm24Zn4 were prepared by module assembly.Quantum Monte Carlo calculation shown that it exists the antiferromagnetic coupling interaction between Gd3+ ions,revealing the internal factor of weak magnetocaloric effect of compound Gd24Zn4.3)Finally,acetate and propionate.as the mixed ligands with the mixed anion templates,series of high-nuclearity lathanide-transition metal clusters Ln45M7(Ln = Gd3+/Dy3+,M = Co2+/Ni2+)were obtained.Magnetic studies indicated that compounds Gd45M7 have a large magnetocaloric effect and compounds DyasM7 display slow magnetic relaxation.4.Syntheses,Structures and Magnetic Properties of High-nuclearity Lanthanide-Iron Metal Clusters Based on Acetate and Polyol Mixed Ligands.1)When triethanolamine is used as an organic base and the pH of the solution is adjusted to be slightly alkaline,CO32-as anion template is slowly formed by fixing CO2 frorm atmosphere and a lanthanide-iron cluster Y7Fe9 with the triangular configuration was obtained.2)When acetate was used as a carboxylic acid and trienthanolamine was used to adjuste the pH of the solution while action as an auxiliary ligand for the polyol,a series of high-nuclearity lanthanide-iron clusters Lni2Fei4(Ln = Gd3+/Y3+/Eu3+)were obtained.High-reolustion mass spectrometry and dynamic light scattering proved the stability of compound Gd12Fe14 and Y12Fe14 in solution.And the core-shell monodisperse nanoparticles Gd12Fe14@SiO2 and Y12Fe14@SiO2 were prepared through facile one-pot microemulsion method.Magnetic studies indicated that encapsulation of one cluster into one silica nanosphere not only effectively decreases intermolecular magnetic interaction but also significantly increases the zero-field splitting effect of the outer layer Fe3+ ions.3)When the chiral ligand trans-4-hydroxyl-L-proline was chosen as the carboxylic acid ligand and triethanolamine ws used as an organic base and a secondary ligand for the poloy,series of racemic high-nuclearity lanthanide-iron clusters Yi2Fe33,Gdi2Fe33 and Yi6Fe29,Gd16Fe29 featuring magnetite configuration were obtained,which possessed the highest nuclear number in the reported lanthanide-iron clusters so far.Single crystal analysis shown that compounds Lni2Fe33 and Ln16Fe29 have the same iron-oxo e-Keggin type {Fe13} which is the magnetite assembly motif in nature.