Synthesis, Crystal Structure And Properties Research Of Polyoxometalate-based Inorganic-Organic Hybrid Materials

Polyoxometalates have been attracting a lot of attention due to their unique property, various structures and vast species. The development of polyoxometalate chemistry marches on multinucleation and chemical modification. In this thesis, phosphonopropionic acid and N-（phosphonomethyl）-iminodiacetic acid were chosen as the organic component of inorganic-organic hybrids and used to synthesize（1） new organo-modificated polyoxometalates and（2） phosphonopropionate-containing inorganic-organic hybrid polyoxometalate compounds with multidimensional structure. The influences of the acidity of solution, reaction temperature, reaction time on product structure have been investigated and eleven new hybrid compounds were obtained with conventional and hydrothermal methods. Further, some properties of the hybrids have been studied by XRPD, elemental analysis, IR spectroscopy, thermogravimetric analysis, fluorescence and solid ultraviolet diffuse spectroscopy, magnetic property. The relationships between properties and structures for the hybrids have been also analyzed.1. In order to explore the reactivity of phosphonocarboxylate derivatives of pentamolybdodiphosphate anion, molybdate, transition metal ions（Co2+, Fe2+ and Cu2+）, phosphonopropionic acid and 4,4’-bipyridine（bipy） were chosen as starting materials and carry out the reaction in aqua solution. Four new compounds of pentamolybdodiphosphonopropionate were obtained. [Co3（bipy）4（H2O）6{（HO2CC2H4PO3）2Mo5O15}2]·（H2bipy）2·18H2O（1） [Fe3（bipy）4（H2O）6{（HO2CC2H4PO3）2Mo5O15}2]·（H2bipy）2·18H2O（2） [Cu（bipy）（H2O）2{（HO2CC2H4PO3）2Mo5O15}]·（H2bipy）·4H2O（3） [H3O]2[{Cu6（bipy）10（H2O）4}{Cu2（bipy）2（H2O）4}{（HO2CC2H4PO3）Mo5O15（O2CC2H4P O3）}2{（HO2CC2H4PO3）2Mo5O15}2]·30H2O（4）Carboxyl-functionalized Strandberg-type polyoxometalate anion, [（HO2CC2H4PO3）2Mo5O15]4-, formed in situ acts as a tridentate ligand in 1 and 2 or a bidentate ligand in 3 and link metal ions together with bipy, forming different 2D frameworks. The different 2D frameworks lead to different photoluminescent emissions and magnetic exchange.The compound 4 has a 3D inorganic-organic framework structure. This compound is the first example that carboxylic-functionalized pentamolybdodiphosphate anions acts as a four dentate ligand including the coordination of the carboxylic groups. The coordination of the carboxylic groups of [（HO2CC2H4PO3）2Mo5O15]4– to Cu2+ ions plays a crucial role in the formation of the three dimensional covalence framework. This compound is also an excellent example that the photoluminescent property of a compound definitely depends on the structure.2. Using 3-Phosphonopropionic acid, molybdate, transition metal ions Cu2 + / Ni2 + and 4, 4 ’- bipyridine as starting materials leads to two Keggin-based hybrids with 4,4’-bipyridine–dedicated Ni/Cu- monosubstituted POMs by hydrothermal methods.（4,4’-H2bipy）2[PNi（4,4’– Hbipy） Mo11O39]·4H2O（5）（4,4’-H2bipy）1.5[PCu（4,4’– Hbipy）Mo11O39]·4H2O（6）3-Phosphonopropionic acid is not stable under hydrothermal conditions and its decomposition product, PO43-, was combined in the new compounds. The compounds 5 and 6 have 3D supramolecular structure formed through various hydrogen bonds. Successful synthesis of the compounds showed POMs anion, 4,4 ’- bipyridine coordination model and solution p H value play an important role in the formation of the hybrid materials.3. With hydrothermal method three unreported compounds containing transition ions were obtained by using 4, 4’-bipyridine and ^2-phosphono-aceticacid as organic ligands, transition metal ions and tungstate as inorganic components.[（H2bipy）3（H2Co Co W11O39）]·2H2O（7）{（Hbipy）2[Co（bipy）2（H2O）4]2（Co W12O40）（bipy）2}（8）{[Ni2（bipy）3（H2O）4]（H2W12O40）H2}·5H2O（9）The heteropoly anion of 7 has a center Co atom and a substituted Co atom. These anions link into an anionic chain by sharing the terminal oxygen atom of the substituted atom of the anions. In 8 a heteropolyanions, the complex ions, [Co（bipy）2（H2O）4]2+, construct a supramolecular layer through hydrogen bonds. Compound 9 has a 2D structure forming from metatungstate anions and binuclear Ni-bipy complexes through the coordination of metatungstate anions and bipy to Ni ions. Between the anions, the anionic chains, the complex cations the layers and bipyridine molecules are the hydrogen bonds.The formation of 7-9 shows that the solution acidity and reaction time influence greatly the structure of the compounds. Solid ultraviolet diffusion results indicate that the compounds 7-9 are potential wide-gap semiconductor materials. In 7,8 there exists antiferromagnetic interaction.4. A multi-dentate ligand, N-（phosphonomethyl）-iminodiacetic acid（（HO）2P（O）CH2N（CH2COOH）2）, as the organic component of organic-inorganic hybrids, molybdate and nickel ion as inorganic components are used and obtained a new compound（10） under hydrothermal conditions.[Ni4（pzac）4（H2O）8（β-Mo8O26）]·2H2O（10）But it is ^2-pyrazinecarboxylate（pzac） that exists in the product. That is,（HO）2P（O）CH2N（CH2COOH）2 was decomposed and the decomposedproducts reformed the pzac. In 10 the pzac chelates and bridges Ni2+ ions into a Ni-pzac polymeric chain; [β-Mo8O26]4- acts as tetra-dentate ligand, combining the Ni-pazc chains through weak Ni-O covalent interaction into a 3D covalent structure. The results imply that the coordination modes of the octamolybdate anion and the pazc ligand play important roles in the formation of the hybrid materials.Reaction of 3-Phosphonopropionic acid, molybdate, transition metal ions Cr2 + and 4, 4 ’- pyridine under hydrothermal conditions gave a B series of Anderson compound:（Hbipy）2[H6Cr Mo6O24)]（bipy）（11）In 11 anion [H6Cr Mo6O24)]^2- acts as either the donor or the acceptor of the hydrogen bonds which is the force constructing the 3D supramolecular structure. Compound 11 has a strong fluorescent emission from Cr3+ ion.