Design And Synthesis And Properties Of Eight Cyano Lanthanide Metals And Transition Metal Compounds

In recent years, considerable efforts have been put into the design and elaboration of functional materials. Octacyanometallates [M(CN)8]n-(M=Mo, W; n=3,4) with flexible coordination modes and lower symmetries have been aggressively studied. The combination of the [M(CN)8]"" building blocks and the second metal centers has produced various dimensional molecular structures and the resulting materials have displayed interesting properties. The octacyanometallates units in these materials can adopt various geometries, e.g., dodecahedral, square antiprismatic or bicapped trigonal prismatic, depending on the external environments, such as the surrounding ligands. However, there are still some problems in this field. On one hand, the development of octacyano-and lanthanide-based assemblies has been somewhat hampered by the tendency of the lanthanide ions to adopt higher coordination numbers, their ability to easily adapt to given environments, and the absence of design strategies for4f-4d/5d networks. As far as we know, limited examples of octacyanometallate-based lanthanide compounds were documented to date. On the other hand, relatively few studies have focused on the porosities and adsorption/desorption properties, despite of the fact that a large number of [M(CN)8]n--based transition metal compounds have been characterized structurally and magnetically.The current research and development of octacyanometallate-based systems has been reviewed in this thesis, and both the [M(CN)8]n--based lanthanide or transition metal systems have been studied in detail, based on the present problems in this field. In order to construct functional [M(CN)8]n--based materials, fifteen three-dimensional (3D) compounds, including eight [W(CN)8]3--based lanthanide metal compounds and seven [M(CN)8]4--based transition metal compounds, have been synthesized through the slow diffusion or solution mixing methods, using the [M(CN)8]n-units as building blocks to react with series of lanthanide metal ions or transition metal ions. Tb(H2O)4(pyrazine)0.5W(CN)8(1) La(H2O)4(pyrazine)0.5W(CN)8(2) Ce(H2O)4(pyrazine)0.5W(CN)8(3) Pr(H2O)4(pyrazine)0.5W(CN)8(4) Nd(H2O)4(pyrazine)0.5W(CN)8(5) Sm(H2O)4(pyrazine)0.5W(CN)8(6) Eu(H2O)4(pyrazine)0.5W(CN)8(7) Gd(H2O)4(pyrazine)0.5W(CN)8(8)[Mn(H2O)2]2Mo(CN)8·3H2O (9·7H2O)[Mn(H2O)2]2W(CN)8·3H2O (10·7H2O)[Mn(H2O)2]2Mo(CN)8·4H2O (11·8H2O)[Co(H2O)2]2Mo(CN)8·4H2O (12·8H2O)[Fe(H2O)2]2Mo(CN)8·4H2O(13·8H2O)[Cd(H2O)2]2Mo(CN)8·3.5H2O(14·7.5H2O)[Cd(H2O)2]2W(CN)8·3.5H2O(15·7.5H2O)Then the resulting materials were characterized by spectroscopies, thermal analyses, single-crystal X-ray diffraction and (variable-temperature) powder X-ray diffraction, SQUID magnetometer, vapor and gas adsorption analyzers, and so on.For the3D octacyanometallate-based lanthanide metal compounds, the paramagnetic building block [W(CN)8]3-was employed to react with series of lanthanide metal ions Ln3+(Ln=La-Tb) and the pillar N-donor bidentate ligand pyrazine in the acetonitrile solution through the intercalation method, based on the structural features of2D layers Ln(H2O)5W(CN)8and the flexible coordination modes of lanthanide ions, isolating eight isostructural3D [W(CN)8]3"-based lanthanide compounds (1-8). These compounds mark the first structural patterns using neutral2D layers as building blocks and the first3D LnⅢ-WⅤ(CN)8compounds found in the octacyanometallate-based system. The possible formation mechanism and the relationship between structures and magnetic properties have been further investigated. The results showed that the diffusion temperature had played a crucial role for the formation of such3D system. Furthermore, the magnetic properties of these3D materials depend mainly on the lanthanides ions, together the structures and dimensionalities of inorganic cyanide subnetworks involved in frameworks. Importantly, compounds1,3,5,6and8were typical soft magnets.For the3D octacyanometallate-based transition metal compounds,[M(CN)8]4-(M=Mo, W) building blocks were employed to react with series of transition metal ions M’2+(M=Mn, Co, Fe, Cd) using water as the reaction solvent, resulting in the formation of seven3D [M(CN)8]4’-based transition metal compounds (9,10)·7H2O,(11-13)·8H2O and (14,15)·7.5H2O. The thermal stabilities, desorption/adsorption process of water molecules and gas adsorption properties have been studied. In addition, the relationship between structures and adsorption/desorption properties in such system has been further explored. The results showed that the porous features of these compounds were influenced obviously by the number of crystallized water molecules involved in pores and the difference of transition metal ions in frameworks. Among them, dehydrated compounds9and10exhibited typical porosities features and have moderate uptakes for water molecules, nitrogen and hydrogen gases, owing to the fact that all water molecules involved in pores can be removed without structural collapse. However, there are still two coordinated water molecules left in pores after partially dehydration for compounds (11-13)·8H2O, resulting in the small pore size, porosities and almost no uptake for hydrogen gas. There are still no gas uptake for fully dehydrated compounds14and15, although all water molecules can also been removed from pores in compounds (14,15)·7.5H2O, which can be attributed to the much small pore size for both materials. In addition, the coordination environment of metal centers for above seven compounds have changed with the desorption/adsorption of coordination water molecules, thus resulting in the change of porous frameworks. Interestingly, these materials can reversibly adsorb/desorb all crystallized and partial coordinated water molecules. More importantly, the high hydrogen enthalpy for dehydrated compounds9and10can be attributed to the presence of coordinatively-unsaturated Mn2+sites left exposed by the removal of coordinated water molecules in the structure.