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Syntheses, Structures And Properties Of Supramolecular Assemblies Based On Organic Amines And Polyoxometalates

Posted on:2006-07-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z G HanFull Text:PDF
GTID:1101360152486136Subject:Inorganic Chemistry
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In this thesis, a new series of supramolecular compounds based on organic amines andclassical polyoxometalates (POMs) has been synthesized and characterized viaself-assembly under hydrothermal reaction conditions. The physical and chemical propertiesof these compounds, such as thermal stabilities and redox electrochemical behaviors, havealso been researched in detail. Multiple intermolecular interactions drive together thesupramolecuar assembly processes of these compounds. Organic species derived fromsubstituted aromatic amines, formulated: 4-(pyridin-2-yl)pyridine (bpy),4-(5-chloropyridin-2-yl)pyridine (cbpy), 4-(5-phenylpyridin-2-yl)pyridine (ppy) and4-(5-(4-bromophenyl)pyridin-2-yl)pyridine (bppy), with good π-electron conjugated system,may act as π-electron donors' moiety. POM anions may act as electron-accepting moiety.Therefore, these salt-like compounds containing inorganic POM anions and organicaromatic amines may be endowed with interesting physical and chemical properties. Thesecompounds are below: (bpy)4H6[SiMo12O40] (1),(ppy)4H6[SiMo12O40] (2),(ppy)4H6[SiW12O40]·2H2O (3), (ppy)4H5[PMo(12O40]·1.25H2O (4),(ppy)8H3[PW12O40]·2H2O (5), (ppy)4H[PMo12(VO)O40] (6),(cbpy)3H3[PMo12O40]·2.2H2O (7), (bppy)4H5[PMo12O40]·3H2O (8),(bppy)4H6[SiW12O40]·3H2O (9), (bppy)10H5[PW12O40]·5H2O (10),(cbpy)(bppy)2H5[PMo12O40]·H2O (11), (ppy)5H5[PW11O39Co(ppy)]·2H2O (12), {[Ag2(bppy)3][Ag(bppy)2][Ag(bppy)]2PW11Co(bppy)O39}·2H2O (13), (bppy)7H6[P2W18O62]·3.5H2O (14),(bppy)4H4[Mo8O26] (15), (NH4)[Cu(en)2][Na(en)Cu(en)2(H2O)(Mo7O24)]·4H2O (16) All these crystal structures are in low symmetric crystal system: Triclinic or Monoclinic,which may be explained from the structures of spherical inorganic POM anions and planeorganic pyridine derivatives. In these compounds with supramolecular structure, Kegginpolyanions form 1D chain, 1D double-chain, 2D plane and 2D 'wave' layer structures viaintermolecular interactions occurred among surface oxygen atoms from different anionclusters. Most of organic moieties exhibit regular pillar-like arrangements owing to π-πpacking interaction. Intermolecular hydrogen bonding and aryl packing exist extensively in crystal structureof compounds 1-6. Compound 1 forms in the solid state a supramolecular structureH-bonding drives the self-organization of the protonized bpys as helical chains that in turnarrange around the polyoxometalate centers; compound 2 contains alternative arrays ofinorganic and organic layers; compounds 4-6 represent rare organic bicapped Kegginstructures and are supported by supramolecular interactions to extend into a 3D network. Inparticular, the unusual structural feature of compound 6 contains simultaneously organicbicapped and inorganic monocapped structure. In compounds 7-11, intermolecular interactions hydrogen bonding, halogen bondingand aryl packing co-exist in the self-assembly processes of Keggin POMs. The C-X…O (X= Cl, Br) synthon is introduced for the first time to assemble Keggin POMs. The crystalstructure analyses reveal that the substituted groups of organic bipyridine have a majorinfluence on the packing arrangement of crystals. In compound 11, Keggin anion introducesthe self-assembly of organic molecules cbpy and bppy to form a 3D framework structure. By replacing one W with transitional metal Co, compounds 12-13 were obtained.Compound 12 is a monosubstituted tungstophosphate with one pendant tricyclic, aromaticentity ligand, other organic ppys play a role in balancing electronic charge. The structure of13 consists of a 1D chain constructed from a monosubstituted tungstophosphate with onependant conjugated bppy ligand, and five silver-bppy groups. The periphery of the Keggincluster extends its linkages with five Ag-bppy groups into a bicapped trisupporting Kegginstructure. In compounds 14 and 15, the POM anions are replaced with Dawson [P2W18O62]6- andisopolyanion β-[Mo8O26]4...
Keywords/Search Tags:polyoxometalate, organic amine, supramolecular assembly, electrochemistry, hydrothermal synthesis.
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