| Lanthanide metal organic framework compounds (Ln-MOFs), exhibit superior performance in optics, catalysis, gas adsorption and magnetic aspects. In recent years, many attentions have been paid on the rational design and synthesis of coordination compounds of novel Ln-MOFs. In this paper, twenty-eight new Ln-MOFs, which are based on pyrazine-2,3-dicarboxylic acid, pyridine-2,5-dicarboxylic acid and 2,2’-biphenyl dicarboxylic acid ligands, have been synthesized and characterized by elemental analyses, IR and X-ray single crystal diffraction. The magnetic properties of some compounds also have been studied. The main results are as follows:1. The syntheses, structures and properties of rare earth coordination compounds based on pyrazine-2,3-dicarboxylateEighteen new rare earth compounds or 3d-4f heteronuclear metal compounds based on pyrazine-2,3-dicarboxylate have been synthesized via hydrothermal method by introducing transition metal ions or assist ligand:{[La2(Ll)3(H2O)2]-5H2O}n(1), {[Ce2(L1)3(H2O)]·2H2O}n(2),{[Pr2(L1)3(H2O)]·2H2O}n(3), {[Nd2(L1)3(H2O)]·2H2O}n(4),{[Sm2(L1)3(H2O)]·2H2O}n(5), {[Dy(L1)(OH)(H2O)3]·3H2O}n(6),{[La2Zn(L1)4(H2O)6]·2H2O}n(7), {[Ce2Zn(L1)4(H2O)6]·2H2O}n(8),{[Pr2Zn(L1)4(H2O)6]·2H2O}n(9), {[Nd2Zn(L1)4(H2O)6]·2H2O}n(10),{[Sm2Zn(L1)4(H2O)6]·2H2O}n(11), {[Dy2Zn(L1)4(H2O)6]·2H2O}n(12),{[Ce2Cd(L1)4(H2O)6]·2H2O}n(13), {[Nd3Zn6(Ll)6(OAc)2(OH)7(H2O)3]·8H2O}n(14),{[Pr2(Ll)2(ptz)(H2O)8]·8H2O}n(15), {[Nd2(L1)2(ptz)(H2O)8]·8H2O}n(16),{[Gd(H2O)8]2(ptz)3·6H2O}n(17), {[Yb(H2O)8]2·(ptz)3·6H2O}n(18).Compounds 1-5 have the same synthetical conditions. But pyrazine-2,3-dicarboxylate ligands were taken different coordination modes, which linked rare earth metal ions to form a three dimensional network structure. When the reaction temperature rised and reaction time extended, only compound 6 with a one-dimensional chain structure had been synthesied. Compounds 7-13 are synthesized under the same reaction conditions by the introduction of different transition metal ions (ZnⅡ, CdⅡ). Six Ln-Zn heteronuclear metal compounds (compounds 7-12) and one Ln-Cd heteronuclear metal compound (compound 13) are synthesized. In compound 14, NdⅢ and ZnⅡ are linked by pyrazine-2,3-dicarboxylate ligands, bridging water molecules and hydroxyl groups to form a cage structure{[Nd3Zn6(Ll)6(OAc)2(OH)7(H2O)3]·8H2O}. Compound 14 is one-dimensional coordination chain, with the cage-like structure as repeating unit. In compounds 15 and 16, pyrazine-2,3-dicarboxylate ligands link rare earth metal ions to form a two-dimensional layered structure, which is further connected by ptz2- ligands via hydrogen bonds to form a three dimensional network structure. In compounds 17 and 18, rare earth metal ions are coordinated by water molecules, which are further connected by ptz2- ligands via hydrogen bonds to form a three dimensional network structure.By comparing the syntheses conditions and structures of compounds 1-18, it can be concluded the following law:(a) compared to heavy rare earth metal (Dy, Gd), light rare earth (La, Ce, Pr, Nd, Sm) are more easy coordinated by heterocyclic carboxyliate ligands, with the higher number of coordinated. And most of these compounds can form a three-dimensional network structure. Thus, the structures of rare earth metal ions have a significant impact on building compounds, (b) The transition metal, mainly ZnⅡ and CdⅡ, are easier to build heteronuclear rare earth compounds. When introducing other metal ions (MnⅡ, CoⅡ, NiⅡ etc.), only the same nucleus of rare earth compounds or transition metal compounds are synthesized. It is visible that rare earth metals in the formation of heteronuclear compounds have certain selectivity on the transition metals. (c) In the same synthetic condition, different ratio of raw materials lead to different structures of synthetic compounds.2. The syntheses, structures and properties of rare earth coordination compounds based on pyridine-2,5-dicarboxylateFour new compounds based on pyridine-2,5-dicarboxylate have been synthesized via hydrothermal method by introducing ZnⅡ transition metal ion: {[Ce2Zn(L2)4(H2O)8·2H2O}n(19),{[Er2Zn(L2)4(H2O)8·2H2O}n(20), {[Yb2Zn(L2)4(H2O)8·2H2O}n(21) and [Er2(L2)2(C2O4)(H2O)4]n(22)Compounds 19,20 and 21 are isomorphic Ln-Zn heteronuclear metal compounds. Ligands in two different modes connect the rare earth ions into form a two-dimensional plane. compound 22 is a two-dimensional structure. Pyridine-2,5-dicarboxylate ligands connect ErⅢ ion into a one-dimensional chain and C2O42- ion chelate ErⅢ ions further, connecting the one-dimensional chain to a two-dimensional plane. Magnetic susceptibility measurements indicate antiferromagnetic interactions within ErⅢ ions in 20 and within YbⅢ ions in 21.3. The syntheses, structures and properties of coordination compounds based on 2,2’-biphenyl dicarboxylateSix new compounds based on 2,2’-biphenyl dicarboxylate have been synthesized via hydrothermal method or solvent evaporation method:[La2(L3)3(H2O)2]n (23), [Pr2(L3)3(H2O)2]n (24), [Gd2(L3)3(H2O)2]n (25), [Tb2(L3)3(H2O)2]n (26), {[Co3(L3)3(Me2NH)2]·(Me2NH)}n (27) and [Cu(L3)(bpy)]n(28).Compounds 24,25 and 26 are isomorphic rare earth metal compounds and compounds 27 and 28 are transition metal compounds with independent structures. The asymmetric unit of compound 26 contains two crystallographically independent TbⅢ ion, three L32-ligand and two Coordinated H2O molecules. Ligands in two different modes connect TbⅢ ions to form a 1D coordination chain. In compound 27, the Con centers are connected by μ2-η2 mode L32- ligands to form a Co3 cluster, which is further linked to form a 1D coordination chain along the a direction by syn-syn-μ2-η1.η1 mode L32- ligands. In compound 28, each CuⅡ ion is chelated by two L32- ligands and each L32- ligand connects two CuⅡ ions to form a 1D Cu-L3 chain. The two directional Cu-bpy chains intersect alternately with the Cu-L3 chains to form a 3D coordination network. Magnetic susceptibility measurements indicate ferromagnetic interaction within Co3 metal cluster ions in 27 and antiferromagnetic interactions within GdⅢ ions in 25, within TbⅢ ions in 26 and within CuⅡ ions in 28.H2L1=pyrazine-2,3-dicarboxylic acidH2ptz=5,5’-(1,4-phenylene)-two-(1H-tetrazole)H2L2=pyridine-2,5-dicarboxylic acidH2L3=biphenyl-2,2’-dicarboxylic acidbpy=4,4’-bipyridine... |
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