The Study Of The Modification Of Vanadium-containing Polyoxometalates Using Transition-metal Complexes

The aim of this thesis is the synthesis of new polyoxometalate derivatives based on vanadium-containing polyoxoanion building blocks, which are decorated or bridged by various transition metal compounds. By using N-donor ligands of different traits such as 2, 2'-bipyridine (2, 2'-bipy), 1, 10'-phenanthroline (phen), dipyrido[3, 2-d:2', 3'-f]quinoxaline) (dpq), 4,4'-bipyridine (4,4'-bipy) and 1, 1'-(1, 4-butanediyl)bis(imidazole) (bbi), a new series of functional derivatives with isolated or extended structures based on {V15O36(Cl)}, {V16O38(Cl)}, {As8V14O42} and {PM12O40(VO)2} (M=Co or Ni) clusters have been synthesized. Furthermore, we also extended the study on the modification of the Keggin and Wells-Dawson building blocks using flexible ligand.Twenty-two new polyoxometalate compounds have been synthesized on the basis of hydrothermal technique and structurally characterized by elemental analyses, IR, EPR, XPRD, TG and single crystal X-ray diffractions. The study on synthetic conditions and rules for these new compounds are carried out. The physical and chemical properties of these compounds, such as thermal stabilities and redox electrochemical behaviors have also been researched in detail.1. Eight new hybrid inorganic-organic polyoxovanadate derivatives have been synthesized by using rigid chelate bidentate N-donor ligands of 2, 2'-bipy, phen and dpq. [Cu(2, 2'-bipy)3]2[H4V16O38Cl]·4H2O (1) [Cu(2, 2'-bipy)3]3[V15O36Cl]·3H2O (2) [Ni(phen)3]2{[V15O36Cl]0.5[V17O40Cl]0.5}·H2O (3) [Cu(phen)2]4[As8V14O42(H2O)] (4) [Cu(dpq)2]4[As8V14O42(H2O)]·2H2O (5) H2[Cd(phen)3]2{[Cd(H2O)(phen)2](V16O38Cl)}·2.5H2O (6) H2[Cd(2,2'-bipy)3][Cd(H2O)(2,2'-bipy)2]{[Cd(H2O)(2,2'-bipy)2](V16O38Cl)}·1.5H2O (7) H2[C(CH2OH)3NH3]0.5[Cd(phen)3]{[Cd(H2O)(phen)2]2(V16O38Cl)}0.5{[Cd(H2O)(phen)2]2(V16O39Cl)}0.5·2H2O (8)All these structures in compounds 1–8 are zero-dimensional. The second metal-organic subunits act as the counter ions and space-filling units in compounds 1–5. Compounds 1 and 2 are based on [V16O38(Cl)]8- and [V15O36(Cl)]6- building blocks, respectively. They were synthesized under the same reaction condition but in different pH range, which shows that the pH value of the reaction plays a key role in the structural control of self-assemble process. Compounds 4 and 5 exhibit two types of configurations of low-oxidation state arsenic-vanadium clusters, which are the [β-As8V14O42]4- and the [α-As8V14O42]4-. They were synthesized under the same condition but by using different chelate ligands of phen and dpq, which illustrates that the initial reagent has important influence on the microstructure of the inorganic oxide. Compounds 6–8 are the hexadecavanadate derivatives decorated by the transition metal Cd complexes of [CdLx]. The [CdLx] subunits in these compounds act as both the counter ions and the pendent groups which coordinate with the polyoxoanion framework and help to consolidate the structure.Furthermore, compounds 6 and 7 bulk-modified carbon paste electrodes 6-CPE and 7-CPE exhibit bifunctional electrocatalytic activities toward both oxidation and reduction of nitrite, reduction of bromate, as well as oxidation of ascorbic acid in aqueous H2SO4 solutions, and they exhibit good electrocatalytic stability. It is promising to use them as a kind of new-style electrochemical sensors.2. Two novel isostructural hexadecavanadate frameworks have been synthesized by using rigid bridging bidentate ligand of 4, 4'-bipy. (4,4'-bipy)[Zn(4,4'-bipy)2]2[H4ClV16O38]·6H2O (9) (4,4'-bipy)[Co(4,4'-bipy)2]2[H4ClV16O38]·6H2O (10)Compounds 9 and 10 are three-dimensional (3D) open frameworks constructed from four-connecting [V16O38Cl]8- polyoxoanions and six-connecting M2+(M=Zn or Co). The synthesis of these compounds opens a new route in designing POMs-based porous polymer materials.3. Ten high-dimensional polyoxometalate derivatives based on {As8V14O42}, {V16O38Cl}, {PM12O40(VO)2} (M=Mo or W) and {PW12O40} clusters have been constructed by using bridging ligand containing flexible butyl backbone. [M(bbi)2]2[As8V14O42(H2O)] [M=Co (11), Ni (12) and Zn (13)] [Cu(bbi)]4[As8V14O42(H2O)] (14) [Cu(bbi)]6[V16O38Cl] (15) (bbi)1.5[Cu(bbi)]4.5[PW12O40]1.5 (16) M1.5(bbi)4[PW12O40(VO)2]·H2O [M=Co (17) and Ni (18)] M1.5(bbi)4[PMo12O40(VO)2]·H2O [M=Co (19) and Ni (20)]The polyoxoanions in these compounds all exert the special template role. Compounds 11–13 exhibit two-dimensional network based on four-connecting [As8V14O42]4- clusters and six-connecting transition metal ions (M = Co2+ (11), Ni2+ (12), Zn2+ (13)). The topology can be represented by the Schl?fli symbol of (34·42)(34·44·5434·63)2. Compound 14 shows a 3D structure which is composed of [As8V14O42]4- polyoxoanions and [Cu-bbi]+ cationic subunits. It represents the first example of 3D motif based on [As8V14O42]4- building block. Compound 15 displays 3D structure based on [V16O38Cl]6- polyoxoanion and [Cu-bbi]+ subunits with an S-shaped metal-organic segment forming around two ellipsoidal V16 polyoxoanions. Compound 16 is a novel polyoxometalate derivative based on the [PW12O40]3- polyoxoanion and [Cu-bbi]+ cationic subunits. Both the coordinating and the uncoordinating polyoxanions in this compound exhibit the template role, inducing the formation of the [Cu(bbi)]4.5[PW12O40] poly-chain subunits and the (bbi)[PW12O40]0.5 single-chain. Compounds 17–20 exhibit three-fold interpenetrated 3D motifs based on bicapped-Keggin [PM12O40(VO)2]3- (M=W(17–18) or Mo (19–20)) building blocks. There are a few of reports on the interpenetration structure containing polyoxoanions. Such kind of three-fold interpenetrated 3D network structures is reported at the first time in polyoxometalate chemistry.4. Two novel compounds based on [α-P2W18O62]6?and [V16O38Cl]5- have been constructed by using mixed rigid ligand of phen and flexible ligand of bbi at the same time. H2(bbi)0.5[Ni(phen)(bbi)2]2[P2W18O62] (21) [Cu2(phen)2(bbi)]2[Cu(bbi)] [V16O38Cl]·H2O (22) Compound 21 exhibits a tetrasupporting Wells-Dawson type polyoxometalate structure where four [Ni(phen)(bbi)2]2+ fragments are supported on the two polar {W3O13} triads symmetrically. Through the O–Ni–O linkages, the [P2W18O62]6? polyoxoanions form an interesting wavelike chain along the C3 axis. Compound 22 displays a {V16O38Cl} cluster-based homochiral 3D framework induced by infinite cationic single-stranded left-handed helix chains of [Cu(bbi)]n.