The Synthesis,Structure And Properties Of Metal Organic Frameworks Containing Imidazole Salt

Metal-organic frameworks(MOFs)are a kind of ordered crystal material formed by self-assembly of organic ligands and metal centers.MOFs are featured by their larger specific surface area,higher porosity,more diverse structure and function,and has been widely used in catalytic reactions,sensors,gas adsorption and separation,drug transport and other fields[1-3].Therefore,the rational design of functional materials has become a hot topic recently.In this paper,we have synthesized carboxylate acid ligand bearing functional imidazole salt,which could react with rare earth metal ions under different conditions to afford a series of novel MOFs.Spectroscopic analysis,X-ray powder diffraction and X-ray single crystal diffraction are used to characterize the complexes and some complexes has shown thermal stability and fluorescence properties.The main work of this thesis is as follows:1.The ligand,5-(1H-imidazol-1-yl)isophthalic acid ligands have been synthesized and 10 rare earth complexes with single crystal structure have been obtained by hydrothermal reaction.According to the different ligand configuration,these complexes can be divided into three categories:(I)[Ln(H0.5 L)2],[Ln = Gd(1),Tb(2),Dy(3),Er(4),Yb(5)];(II)[Ln(HL)(L)(H2O)2]n,[Ln = Sm(6),Eu(7),Ho(8)];(III){[Ln(HL)(L)(H2O)2]·H2O}n,[Ln = Pr(9),Nd(10)].Complexes 1-10 belong to monoclinic space group P21/c.The crystal structures of 1-5 show that the central metal ions is six-coordinated.The three-dimensional structures can be abstracted as(6,3)-connected network,since each central ion can be considered as a 6-junction node and each ligand a 3-junction node.These structures demonstrate good thermal stability as proven by thermogravimetric analysis.We have also investigated their fluorescent luminescence property and found that complex 2 show good fluorescence performance.For complexes 6-8,their crystal structures show that the central metal ions are eight-coordinated,forming a dodecahedron configuration.Interestingly,ligands with different configurations are assembled with metal ion to give two-dimensional coordination layers first,and then neibourghing layers are connected through the O-H…O,N-H…O hydrgoen bonds to form a 3d supramolecularstructure.The fluorescence property of the complex 7 is explored.For complexes 9-10,their crystal structures exhibit that the central metal ions are nine coordinated to form capped square antiprism.Different from that of complexes 6-8,the aymmetric unit of complexes 9-10 contains a solvent water molecule,which is involved in the formation of hydrogen bonds between the layers,leading to the stabilization of the overall 3D structure.2.The ligand,N-(3,5-two carboxyl phenyl)-N'-(3,5-two carboxyl benzyl)imidazole salt chloride,has been synthesized and hydrothermally reacted with rare earth metal salt to give eight isostructural complexes [Ln(L)(H2O)2]n,[Ln=Nd(11),Sm(12),Eu(13),Gd(14),Tb(15),Dy(16),Er(17),Yb(18)].In their crystal structures,the metal ions are eight-coordinated to give a dodecahedron configuration.The basic building unit of complex is a Ln2(CO2)4 unit,which is bridged by the carboxylate of the ligand.Each building unit is connected by the ligands to form a three-dimensional network of crystal structure.We have studied the thermal stability and fluorescence of the above crystal structures,and found that the complexes possess good thermal stability under 100 ?;However,the complex 15 exhibits the characteristic fluorescent emission.3.The ligand,1,3-bis-(4-carboxyphenyl)imidazolium salt,has been synthesized and hydrothermally reacted with rare earth salt to give eight complexes,being four dinuclear complexes [Ln(L-)2(HL)(Cl-)]n,[Ln = Pr(19),Nd(20),Sm(21),Eu(22)],and four tetranuclear complexes [Ln4(L-)6(HL)2(NO3)6]n,[Ln = Gd(23),Tb(24),Dy(25),Er(26)].The central metal ions of complexes 19-22 are eight coordi-nated to generate a dodecahedron structure.The ligand has two kinds of coordination modes,which is self-assembled with metal ions to form a layered structure.The three-dimensional network structure is formed by intermolecular interaction between layers and layers.For complexes23-26,their central metal ions is nine-coordinated to give tricapped trigonal prism tetradecahedron.Ligand has only one coordination mode,which connect the metal ions to give chain-like one-dimensional structure,the neighbouring chains are linked through the intermolecular force to produce a three-dimensional structure.We have investigated their thermal stability and fluorescence properties and found that the complexes possess good thermal stability under 330 ? and complexes 22 and 24 show good fluorescentperformance.