Syntheses, Structures And Properties Of Novel Rare-Earth Substituted Polyoxotungstates

In the present thesis, in the conventional aqueous solution, we introduced organic solubilizers to the reaction system of rare-earth?RE? ions and simple tungstate to tune the reaction behavior of RE ions and then introduced stereochemically active As?, Sb?, Bi?, Se?, Te? as heteroatoms to in-situ construct lacunary polyoxotungstate?POT? fragments to bond more RE ions to prepare novel RE substituted POTs. Under the guidance of this synthetic strategy, upon systematically exploring the influence of the molar ratio of reactants, reaction temperature and pH value of the reaction system on the products, we synthesized novel RE substituted isopolyoxotungstates?iso-POTs?, RE substituted heteropolyoxotungstates?hetero-POTs? and 3d–4f or 4d–4f heterometallic hetero-POTs, which were structurally characterized by multiple techniques. The fluorescence and magnetic properties of some representatives were investigated. This work not only provides a convenient and effective method of preparing novel RE substituted POTs, but also enriches the structural types of polyoxometalates?POMs? and expandes the research areas of POM chemistry.The thesis can be divided into three sections to state my work during the master study:Part 1: By reaction of RE?NO₃?₃·6H₂O, Na2WO4·2H2O, H2C2O4·2H2O in aqueous solution and by the tuning role of different counter cations, four types of oxalate-bridging RE-substituted lacunary Lindqvist iso-POTs were synthesized. When Na+ ions acted as counter cations, RE substituted di-vacant Lindqvist iso-POT dimers Na10[RE2?C2O4??H2O?4?OH?W4O16]2·30H2O?RE = Eu?, Tb?, Dy?, Ho?, Er?, Tm?, Lu???1–7? were obtained. When Na+ and K+ ions were counter cations, RE-substituted mono-vacant Lindqvist iso-POT tetramers K4Na16[RE?C2O4? W5O18]4·60H2O?RE = Eu?, Tb?, Dy?, Ho?, Er?, Tm?, Lu???8–14? were made. When Na+ and Cs+ ions were counter cations, a one-dimensional chain RE substituted di-vacant Lindqvist iso-POT Na2H4[Er2?H2O?4?C2O4?W4O17]·8H2O?15? was isolated. When Na+ and [?CH3?NH2]+ ions were countercations, a one-dimensional doule-chain RE substituted di-vacant Lindqvist iso-POT [H2N?CH3?2]Na2H4[Er2?C2O4?2?OH?W4O16]·14H2O?16? was synthesized. They all were characterized by elemental analyses, IR spectra, X-ray single-crystal diffraction and thermogravimetric analyses. Under the irradiation of a UV lamp, 1 and 8 exhibit the red emission whereas 2 and 9 exhibit the green emission. Alternate current magnetic susceptibility measurements indicate that 2, 9, 4, 11, 5 and 12 don't exhibit the SMM behavior.By reaction of RE?NO₃?₃·6H₂O, Na2WO4·2H2O and [?CH3?2NH]·HCl in aqueous solution and by the combined action of RE cations and pH values, we synthesized three types of RE substituted iso-POTs [H2N?CH3?2]6Na6[RE4?H2O?22W28O94H2]2·113H2O?RE = Pr?, Nd?, Sm???17–19?, Na2[Eu?H2O?7]2[Eu?H2O?5]2[W22O74H2]·20H2O?20? and Na3H2[RE?H2O?4][RE?H2O?5]2 [W22O74H2]·36H2O?RE = Gd?, Tb?, Dy?, Ho?, Er ?, Tm?, Yb?, Lu???21–28?. 17–19 show the one-dimensional chain, 20 exhibits the two-dimensional sheet and 21–28 are isolated structures. ESI–MS spectra and UV spectra under different pH show that 19, 20 and 27 can be stable in aqueous solution. The photoluminescence properties of 19, 20, 22 and 23 have been investigtated.Part 2: In the presence of organic solubilizers, we systematically explored the reactions of stereochemically active NaAsO2, SbCl3, Na₂SeO₃, K₂TeO₃ with RE?NO₃?₃·6H₂O and Na2WO4·2H2O in conventional aqueous solution. By the one-pot reactions of RE?NO₃?₃·6H₂O, Na2WO4·2H2O, NaAsO2 or SbCl3 and dimethylamine hydrochloride, we prepared four types of RE substituted arsenotungstates and two types of RE substituted tungstoantimonates [H2N?CH3?2]8H3[RENa?H2O?4?OH?WO?H2O??B-?-AsW9O33?2]·8H2O?RE = La?, Ce?, Pr???29–31?, [H2N?CH3?2]8Na8{[W3RE2?H2O?8AsO8?OH?][B-?-AsW9 O33]2}2·74H2O?RE = Eu?, Gd?, Tb?, Dy?, Ho?, Y???32–37?, [H2N?CH3?2]6Na24H16{[RE10W16?H2O?30O50]?B-?-AsW9O33?8}·97H2O?RE = Sm?, Eu?, Gd?, Tb?, Dy?, Ho?, Er?, Tm???38–45?, Na4[H2N?CH3?2]10H29[Nd?H2O?7][W16Nd10O50?H2O?34?AsW9O33?8]·26H2O?46?, [H2N?CH3?2]8Na4H26[{Y3?H2O?8W2O4?H2O?2?Sb4O4??SbW9 O33?4]2·87H2O?47?, [H2N?CH3?2]12Na10{[Ho4?H2O?6Sb6O4]?SbW10O37?2?SbW8O31?2}·50H2O?48? and a tungstoantimonate [H2N?CH3?2]2Na8[Sb2W21O71]·40H2O?49?, which were characterized by elemental analyses, IR spectra and X-ray single-crystal diffraction. 29–31 are a class of sandwich-type RE substituted arsenotungstates and 29 displays the obvious electrocatalytic activity on the reduction of the hydrogen peroxide. 32–37 are tetrameric arsenotungstates constructed from two {?W3RE2?H2O?8O7??B-?-AsW9O33?2}8- subunits via two triangular pyramidal {AsO2?OH?} bridges. The stability of 34, 36 and 37 in aqueous solution was studied by UV spectra and ESI–MS spectra. The thermal stability of 32, 35 and 37 was probed by thermogravimetric analyses, variable-temperature IR spectra and variable-temperature powder X-ray diffraction. The fluorescence properties and decay lifetimes of 32, 34 and 35 were also studied. 38–45 consist of eight trilacunary Keggin [B-?-AsW9O33]9- fragments linked by a [RE10W16?H2O?30O50]26+ cluster. The thermal stability of 40, 41 and 43 was studied by thermogravimetric analyses, variable-temperature IR spectra and variable-temperature powder X-ray diffraction. The results of UV spectra showed that 41 and 45 can be stable for eight days in the aqueous solution and the pH stable range of 41 and 45 in the aqueous solution can be 3.9–7.5. The anticancer activities of 41 and 45 aganist human cervical cancer cells?HeLa? and human breast cancer cells?MCF-7? were intensively examined. Moreover, the fluorescence properties of 38, 39, 41 and 42 were also studied. 46 is a one-dimensional chain based on octameric ployoxoanions by RE linkers. 47 is a tetrameric tungstoantimonate constructed from four [B-?-SbW9O33]9– fragments in the tetrahedral distribution mode through a {RE3?H2O?8W2O4?H2O?2?Sb4O4?}21+ cluster, in which a rare?Sb4O4?4+ cluster is seen. 48 is a tetrameric tungstoantimonate made up of two divacant Keggin [SbW10O37]11– fragments and two tetravacant Keggin [SbW8O31]11– fragments connected by a [Ho4?H2O?6Sb6O4]22+ cluster core.By reactions of Na₂SeO₃, K₂TeO₃ with RE?NO₃?₃·6H₂O and Na2WO4·2H2O, we synthesized eight types of RE-substituted selenotungstates and two types of RE-substituted tungstotellurites Na13H8[Ce?SeW17O59?2]·31H2O?50?, [?CH3?2NH2]4H2[Ho6?H2O?12SeO2][Se2W14O52]2·18H2O?51?, Na4K8H5[W3RE2?H2O?3O6?NO3?]?SeW9O33?2?Se2W14O52?·41H20?RE = Ce?, Pr?, Nd???52–54?, [H2N?CH3?2]10Na2H20[RE4?H2O?12W8O28?SeW9O33?4]·4Cl·50H2O?RE = Dy?, Ho?, Tm?, Lu???55–58?, [H2N?CH3?2]10Na2H24[Er4?H2O?12W8O28?SeW9O33?4]·50H2O?59?, [H2N?CH3?2]2 Na15K2H21{[RE4W4Se4O24?H2O?3]?Se2W14O52?2}2·71H2O?RE = Tb?, Dy?, Ho?, Er?, Tm?, Yb???60–65?, [H2N?CH3?2]7H11[RE2?H2O?8?Se2W16O60H4?][RE2W3O7?H2O?6?SeW9O33?2]2·66H2O?RE = Sm?, Eu?, Gd?, Tb?, Dy?, Ho?, Tm???66–72?, [H2N?CH3?2]2Nd0.5Na3.5H19 {[Nd2?H2O?9?Se2W16O60?][W3Nd2?H2O?5O8?SeW9O33?2]2}·29H2O?73?, [H2N?CH3?2]10H22[RE2W4 O11?H2O?5?SeW9O33?3]2·59H2O?RE = La?, Ce???74–75?, [H2N?CH3?2]18Na12H8{[W16La10?H2O?34 O56][SeW9O33]8}·100H2O?76?, [H2N?CH3?2]4Na2H32{[W18RE10?H2O?38O50][SeW9O33]8}·93H2O?RE = La?, Ce?, Pr???77–79?, [H2N?CH3?2]4Na30K22[Ce4?CH3COO?2W2Te?H2O?3O9]2 [TeW8O30]2[Te2W18O67]2·20Cl·58H2O?80? and [H2N?CH3?2]12Na6H22{Ce2?H2O?5W4O12?TeW9 O33?2}4·36H2O?81?, which were structurally characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. 50 is a dimeric selenotungstate formed by a Ce? ion connecting two [SeW17O59]12– fragments and its electrochemical properties were also probed. 51 is composed of two tetravacant Dawson [Se2W14O52]12– subunits sandwiching a unique hexa-RE [Ho6?H2O?12SeO2]18+ cluster. 52–54 consist of two trivacant Keggin [SeW9O33]8– fragment and a divacant Dawson [Se2W16O60H4]12– fragment, forming mixed Keggin-Dawson RE-substituted selenotungstate and the fluorescence properties of 53 and 54 were studied. 55–59 is a type of RE-substituted selenotungstate tetramer construced from four trilacunary Keggin [SeW9O33]8– fragments linked by a [RE4?H2O?12W8O28]4+ cluster and the fluorescence properties of 55, 56, 59 were measured. 61-66 are also a class of RE-substituted selenotungstate tetramer containing tetravacant Dawson [Se2W14O52]12– fragments and fluorescence properties of 62, 63, 64 and 65 were studied. 67–73 are pentameric mixed Keggin-Dawson selenotungstates formed by four trivacant Keggin [SeW9O33]8– fragments and a divacant Dawson [Se2W16O60H4]12– fragment and the fluorescence properties of 67, 68, 70, 71, 72 and 73 were discussed. 74 and 75 are a type of a RE-substituted selenotungstate hexamer contaning six trilacunary Keggin units. Althoug both 76 and 77–79 are octameric RE-substituted selenotungstates, the numbers of central tungsten atoms are different. 80 is a hexameric RE-substituted tungstotellurite including six tetravacant Keggin [TeW8O30] 8– fragments. 81 is an octameric RE-substituted tungstotellurite.Part 3: We introduced organic ligands or the second metal ions to the RE-substituted hetero-POT system and synthesized organic-inorganic hybrid hetero-POTs and 3d–4f or 4d–4f heterometallic hetero-POTs [H2N?CH3?2]6NaH[RE?H2O?4?Ser??AsW11O38?]2·30H2O?RE = Eu?, Gd?, Tb?, Dy?, Ho?, Er?, Tm?, Yb?, Y?, Ser = serine??82–90?, [H2N?CH3?2]6Nax REyHz[RE4?H2O?11W8?Ser?2O20?AsW9O33?4]·38 H2O?RE = Eu?, x = 6, y = 0, z = 4; RE = Gd?, x = 6, y = 0, z = 4; RE = Tb?, x = 5, y = 1, z = 2; RE = Dy?, x = 6, y = 0, z = 4; RE = Ho?, x = 6, y = 0, z = 4; RE = Er?, x = 6, y = 0, z = 4; RE = Tm?, x = 5, y = 1, z = 2; RE = Yb?, x = 6, y = 0, z = 4; RE = Y?, x = 6, y = 0, z = 4??91–99?, [H2N?CH3?2]4Na4H10[Ho4?H2O?10?D-ala?2W6O17] [As2W19O68]2·38H2O?100?, [H2N?CH3?2]8H8[Pr4?Ser?4?H2O?10W8O22][?-SeW9O33]4·40H2O?ala = alanine??101?, [H2N?CH3?2]6Na2H16{[Ho5W7?H2O?14O18?DHCBDO?2]?AsW9O33?5}·39H2O?DHCBDO = 3,4-dihydroxy-3-cyclobutene-1,2-dione??102?, [H2N?CH3?2]5Na2H4[Cu?H2L?] {[Ho0.5Na1.5Cu3?H2O?5]?AsW9O33?2}·9H2O?H6L = 1,3-bis[tris?hydroxymethyl?methylamino] propane??103? and [H2N?CH3?2]4H6[Se2Ho2Zr2O4?H2O?4][Se2W14O52]2?104? [H2N?CH3?2]10H3 [NaHo2?H2O?4?H2PDA?Se2O2?Se2W13O49?2]·14H2O?H2PDA = pyrazine-2,3-dicarboxylic acid??105?. 82–90 are dimeric arsenotungstates with serine ligand built by two monovacant Keggin [AsW11O38]7- fragments connected via two RE ions and the aqueous solution stability of 82 and 84 and the solid-state fluorescence properties of 82 and 84–89 have been examined. 91–99 are composed of four trivacant Keggin [B-?-AsW9O33]9- fragments and a [Eu4W8O45?H2O?10Ser2]30-cluster and the aqueous solution stability of 91 and 93 and the solid-state fluorescence properties of 91 and 93–98 have been investigated. The structure of 100 is similar to 91–99. 101 is the first organic-inorganic hybrid selenotungstate containing a [Pr4?Ser?4?H2O?10?OH?2W8O22]14+ cluster connecting four [SeW9O33]8– subunits. 102 is a pentameric Keggin-type arsenotungstate with square acid ligand. 103 is the first organic-inorganic hybrid 3d–4f heterometallic arsenotungstate with 1,3-bis[tris?hydroxymethyl?methylamino]propane ligand. 104 is the first 4d–4f heterometallic selenotungstate. 105 is a sandwich-type organic-inorganic hybrid selenotungstate with 2,3-pyrazine dicarboxylic acid ligand.