Synthesis And Characterization Of Low-nuclear 4f,High-nuclear 3d-4f Complexes

For more than past two decades,lanthanide based polynuclear metal complexes have been rapidly developed experimentally and theoretically not only because of their fantastic structure,but also owing to their magnetic and optical properties.In this paper,several series of lanthanide based complexes have been successfully synthesized by hydrothermal method and self-assembly approach.They have been characterized by X-ray single crystal analysis,infrared radiation(IR),element analysis,and powder X-ray diffraction(XRD).Magnetic properties and luminescence measurement of them have been analyzed.Among them:1.A series of dinuclear complexes with general formula [Ln2L14(H2O)8](OH)2?2H2O[Ln = Dy(1),Tb(2),Ho(3)and Eu(4);HL1 = 3-(1H-tetrazol-5-yl)benzoic acid]have been synthesized by hydrothermal method and characterized by single-crystal X-ray diffraction.The magnetic properties have been measured,the Dy derivative shows a single–molecule magnet behavior with a zero dc field,fitting by Arrhenius rate law and afford ? = 29.45 K.The luminescence measurement shows that these compounds exhibit characteristic Ln3+luminescence in both visible and near-infrared(NIR)regions.2.Two dinuclear complexes have been obtained by self-assembly approach according to two different Schiff-baesd ligands.The structural and magnetic properties of two Dy-based complexes have been measured and compared.They share the formula [Dy2L2dbm2]NO3 where L = L2(5),L3(6);dbm =Dibenzoylmethane.Complexs 5 and 6 have a very similar structure,however,they show different behavior in magnetic measurement.Complex 6 shows slow magnetic relaxation at low temperature.3.A family of dinuclear complexes with general formula[Ln2L42dbm2(Me OH)2]?3Me OH [Ln = Gd(7),Dy(8),Tb(9),and Ho(10)] have been successfully synthesized and characterized by single-crystal X-ray diffraction.The Dy cluster shows the frequency dependent behavior in magnetic analysis,which suggests slow field induces relaxation of magnetization and fitting by Debye law and afford ? ? 1.85 K,?0 ? 2.15 × 10-6 s.And the luminescence study of these complexes shows that these compounds exhibit characteristic Ln3+luminescence.4.A series of [Ln12Zn] [Ln = Gd(11),Sm(12),Eu(13)] clusters have been successfully synthesized by the self-assembly reaction of ligand H3L5 with zinc chloride and rare earth nitrates at room temperature,and their structures have been characterized.X-ray diffraction shows that the complex has a novel structure and there are two identical structural units within the molecule.The two structural units are connected by Zn(II)ions,and each unit contains a center Zn(II)ion and six Ln(III)ions,and shows a Single cap triangular prism structure.The three Ln(III)ions in the bottom triangle of the structural unit are nine-coordinated,and the remaining three Ln(III)ions are in the eight-coordinated mode.The magnetic data for the complexes 11-13 show that the complexes are antiferromagnetic,the calculated magnetic entropy of the complex 11 is pretty higher,?Sm = 30.79 J kg-1K-1,possess a much larger magnetocaloric effect.