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ABSTRACT: Polyoxometalates (POMs) have demonstrated the unusual ability to both stabilize nanoclusters and facilitate catalytic activity by allowing substrate access to sufficient metallic surface area. This paper presents a wet chemical synthetic method to prepare Pd, Ag, and Au metal nanoclusters stabilized by tetrabutylammonium salts of Phosphotungstates with the well-known Keggin [α-PW(12)O(40)](3-) (PW(12)), Wells-Dawson [P(2)W(18)O(62)](6-) (P(2)W(18)), and their lacunary derivatives [α-PW(11)O(39)](7-) (PW(11)) and [P(2)W(15)O(56)](12-) (P(2)W(15)) structures. The preparation of this series of nanoclusters has facilitated a comparison of the effect these anions have in nanocluster stabilization and catalysis. The nanocluster systems were found to be re-dispersible in acetonitrile and acetone. The effect of aging on stability was followed over 3months and it was found that many systems were very stable for more than 70days without precipitation, depending on type of polytungstate stabilizer and the presence of competing ions. The PW(12), P(2)W(18), PW(11), and P(2)W(15) stabilized Pd nanoclusters have been investigated for catalytic activity in the hydrogenation of 1-hexene and were found to be very active with the P(2)W(18) stabilized Pd nanoclusters demonstrating a best of 139,000 Total Turnovers, thus ranking this "soluble heterogeneous catalyst" among one of the longest lived reported in the literature. The nanocluster systems were characterized using instrumental techniques such as UV-Visible Spectroscopy, FTIR Spectroscopy, Powder X-ray Diffraction, Energy Dispersive Spectroscopy, X-ray Photoelectron Spectroscopy, and Transmission Electron Microscopy.
Journal of Colloid and Interface Science 01/2013; · 3.07 Impact Factor
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Maria Barsukova-Stuckart,
Natalya V Izarova,
Ryan A Barrett,
Zhenxing Wang,
Johan van Tol,
Harold W Kroto,
Naresh S Dalal,
Pablo Jiménez-Lozano,
Jorge J Carbó,
Josep M Poblet,
Marc S von Gernler,
Thomas Drewello,
Pedro de Oliveira,
Bineta Keita, Ulrich Kortz
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ABSTRACT: A total of 16 discrete polyoxopalladates(II) [MO(8)Pd(II)(12)L(8)](n-), with a metal ion M encapsulated in a cuboid-shaped {Pd(12)O(8)L(8)} cage, have been synthesized: the phenylarsonate-capped series (1) L = PhAsO(3)(2-), M = Sc(3+) (ScPhAs), Mn(2+) (MnPhAs), Fe(3+) (FePhAs), Co(2+) (CoPhAs), Ni(2+) (NiPhAs), Cu(2+) (CuPhAs), Zn(2+) (ZnPhAs); the phenylphosphonate-capped series: (2) L = PhPO(3)(2-), M = Cu(2+) (CuPhP), Zn(2+) (ZnPhP); and the selenite-capped series (3) L = SeO(3)(2-), M = Mn(2+) (MnSe), Fe(3+) (FeSe), Co(2+) (CoSe), Ni(2+) (NiSe), Cu(2+), (CuSe), Zn(2+) (ZnSe), Lu(3+) (LuSe)). The polyanions were prepared in one-pot reactions in aqueous solution of [Pd(3)(CH(3)COO)(6)] with an appropriate salt of the metal ion M, as well as PhAsO(3)H(2), PhPO(3)H(2), and SeO(2), respectively, and then isolated as hydrated sodium salts Na(n)[MO(8)Pd(II)(12)L(8)]·yH(2)O (y = 10-37). The compounds were characterized in the solid state by IR spectroscopy, single-crystal XRD, elemental and thermogravimetric analyses. The solution stability of the diamagnetic polyanions ScPhAs, ZnPhAs, ZnPhP, ZnSe, and LuSe was confirmed by multinuclear ((77)Se, (31)P, (13)C, and (1)H) NMR spectroscopy. The polyoxopalladates ScPhAs, MnPhAs, CoPhAs, and CuPhAs were investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). Electrochemical studies on the manganese- and iron-containing derivatives demonstrated that the redox properties of the Mn(2+), Fe(3+), and Pd(2+) centers in the polyanions are strikingly influenced by the nature of the capping group. These results have subsequently been verified by density functional theory (DFT) calculations. Interestingly, electron paramagnetic resonance (EPR) measurements suggest that the coordination geometry around Mn(2+) is dynamically distorted on the EPR time scale (∼10(-11) s), whereas it appears as a static ensemble with cubic symmetry on the X-ray diffraction (XRD) time-scale (10(-15) s). The octacoordinated Cu(2+) cuboid is similarly distorted, in good agreement with DFT calculations. Interestingly, g(∥) is smaller than g(⊥), which is quite unusual, needing further theoretical development.
Inorganic Chemistry 11/2012; · 4.60 Impact Factor
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ABSTRACT: The synthetic macrocycle cucurbit[6]uril forms host-guest inclusion complexes with molecular dibromine and diiodine. As evidenced by their crystal structures, the encapsulated dihalogens adapt a tilted axial geometry and are held in place by two different types of halogen bonding interactions, one with a water molecule (bond distances 2.83 Å for O---Br and 3.10 Å for O---I) and the other one with the ureido carbonyl groups of the molecular container itself (bond distances 3.33 Å for O---Br and 3.49 Å for O---I). While the former is of the conventional type, involving the lone electron pair of an oxygen donor, the latter is perpendicular, involving the π system of the carbonyl oxygen (N-C=O---X dihedrals ca. 90°). Such perpendicular interactions resemble those observed in protein complexes of halogenated ligands. A statistical analysis of small-molecule crystal structural data, as well as quantum-chemical calculations with urea as a model (MP2/aug-cc-pVDZ-PP), demonstrate that halogen bonding with the π-system of the carbonyl oxygen can become competitive with the commonly favored lone-pair interaction whenever the carbonyl group carries electron-donating substitutents, specifically for ureas, amides, and esters, and particularly when the lone pairs are engaged in orthogonal hydrogen bonding (hX bonds). The calculations further demonstrate that the perpendicular interactions remain significantly attractive also for nonlinear distortions of the O---X-X angle to ca. 140°, the angle observed in the two reported crystal structures. The structural and theoretical data jointly support the assignment of the observed dihalogen-carbonyl contacts as genuine halogen bonds.
Journal of the American Chemical Society 11/2012; · 9.91 Impact Factor
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Maria Barsukova-Stuckart,
Luis F Piedra-Garza,
Bimersha Gautam,
Gabriela Alfaro-Espinoza,
Natalya V Izarova,
Abhishek Banerjee,
Bassem S Bassil,
Matthias S Ullrich,
Hans J Breunig,
Cristian Silvestru, Ulrich Kortz
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ABSTRACT: Three discrete organoantimony(III)-containing heteropolytungstates [(PhSb(III))(4)(A-α-Ge(IV)W(9)O(34))(2)](12-) (1), [(PhSb(III))(4)(A-α-P(V)W(9)O(34))(2)](10-) (2), and [{2-(Me(2)NCH(2)C(6)H(4))Sb(III)}(3)(B-α-As(III)W(9)O(33))](3-) (3) have been synthesized in one-pot reactions in aqueous medium using the appropriate lacunary heteropolyanion precursor and organoantimony(III) source. Polyanions 1-3 were isolated as hydrated salts, (NH(4))(12)[(PhSb(III))(4)(A-α-Ge(IV)W(9)O(34))(2)]·20H(2)O (1a), Rb(9)Na[(PhSb(III))(4)(A-α-P(V)W(9)O(34))(2)]·20H(2)O (2a), and Rb(3)[{2-(Me(2)NCH(2)C(6)H(4))Sb(III)}(3)(B-α-As(III)W(9)O(33))]·7H(2)O (3a). The compounds 1a-3a were fully characterized in the solid state using infrared (IR) spectroscopy, single-crystal XRD, and thermogravimetric and elemental analyses. The stability of 1-3 in aqueous solution was confirmed by multinuclear NMR ((1)H, (13)C, (31)P, and (183)W) spectroscopy. Preliminary studies on the biological activity of 1-3 showed that all three compounds might act as potent antimicrobial agents.
Inorganic Chemistry 10/2012; · 4.60 Impact Factor
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ABSTRACT: The biological significance of polyoxometalates is well renowned owing to their anticancer, antiviral and antibiotic properties. Here another therapeutic aspect of polyoxometalates has been explored as alkaline phosphatase inhibitors along with the remarked anticancer and amoebicidal properties. Synthesis and inhibitory studies of a set of seven polyoxotungstates against two major isozymes of alkaline phosphatase i.e. tissue specific and tissue non-specific alkaline phosphatase revealed their promising activity as alkaline phosphatase inhibitors. All compounds exhibited alkaline phosphatase inhibitory potency in nanomolar ranges. For tissue specific alkaline phosphatase, Na(10)[H(2)W(12)O(42)]·27H(2)O () was found to be the most potent inhibitor (K(i) value 313 ± 7 nM), while for tissue non-specific alkaline phosphatase Na(33)[H(7)P(8)W(48)O(184)]·92H(2)O () showed the highest inhibition potency (K(i) values 135 ± 10 nM). Moreover cytotoxicity evaluation of these compounds against lung carcinoma cells and immortalized human corneal epithelial cells demonstrated their anticancer potential with no cytotoxic effects on normal human cell lines. All anticancer drugs result in an impaired immune system and such immunocompromised persons become vulnerable to opportunistic infections specially Acanthamoeba which causes granulomatous amoebic encephalitis (GAE) which almost always results in death. The exclusive property of our tested polyoxotungstates is their strong amoebicidal activity against Acanthamoeba. Hence the study reveals a new window towards cancer therapy with the combined control of elevated levels of alkaline phosphatase and granulomatous amoebic encephalitis in cancer patients.
Dalton Transactions 10/2012; · 3.84 Impact Factor
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ABSTRACT: The discrete heteropolyaurate [Au(III)(4)O(4)(Se(IV)O(3))(4)](4-) () represents only the second member of this class ever reported, and was synthesized via one-pot room temperature condensation in aqueous medium. was structurally characterized in the solid state and in solution by single-crystal XRD, TGA, FT-IR, (77)Se NMR, mass spectrometry and electrochemistry.
Chemical Communications 08/2012; 48(79):9849-51. · 6.17 Impact Factor
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ABSTRACT: Polyoxometalates containing noble metal ions, such as ruthenium, osmium, rhodium, palladium, platinum, silver and gold, are a structurally diverse class of compounds. They include both classical heteropolyanions (vanadates, molybdates, tungstates) in which noble metals are present as heteroatoms, as well as the recently discovered class of polyoxometalates with noble metal "addenda" atoms. The focus of this Review is on complexes that should, in principle, exist as discrete molecular species in solution, and which are therefore of interest for their reactivity, their future synthetic utility and potential applications, for example, in catalysis or nanoscience.
Angewandte Chemie International Edition 08/2012; 51(38):9492-510. · 13.45 Impact Factor
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ABSTRACT: In the wide area of polyoxometalate (POM) chemistry, diphosphate/diphosphonate-based POMs represent a more recent area of study. However, in this short time it has emerged to become very dynamic, as shown by the wide variety of compounds reported. Ever since the discovery of the first polyoxotungstate framework constructed from diphosph(on)ate ligands, a widespread investigation on the preparative chemistry and properties of such compounds has followed. The main focus of such a study is based on factors such as the oxidation state of the metal, the effect of pH and temperature during synthesis, and the presence of different functional groups on the diphosphonate. In this review we discuss in detail all diphosphate/diphosphonate-based POMs, beginning with early developments, subsequent growth in interest, and finally focusing on the very latest developments.
Chemical Society Reviews 07/2012; 41(22):7590-604. · 28.76 Impact Factor
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ABSTRACT: The reaction of [Sb(2)W(22)O(74)(OH)(2)](12-) and [Fe(4)(H(2)O)(10)(β-TeW(9)O(33))(2)](4-) with (NH(4))(2)[RuCl(6)] in aqueous solution resulted in the novel ruthenium(IV)-containing polyanions [{Ru(IV)(4)O(6)(H(2)O)(9)}(2)Sb(2)W(20)O(68)(OH)(2)](4-) and [{Ru(IV)(4)O(6)(H(2)O)(9)}(2){Fe(H(2)O)(2)}(2){β-TeW(9)O(33)}(2)H](-), exhibiting two cationic, adamantane-like, tetraruthenium(IV) units {Ru(4)O(6)(H(2)O)(9)}(4+) bound to the respective polyanion in an external, highly accessible fashion.
Inorganic Chemistry 07/2012; 51(14):7442-4. · 4.60 Impact Factor
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ABSTRACT: Interaction of potassium antimony(iii) tartrate hydrate K(2)(SbC(4)H(2)O(6))(2)·3H(2)O with the trilacunary Keggin derivatives [A-α-XW(9)O(34)](10-) (X = Si(IV), Ge(IV)) and [A-α-PW(9)O(34)](9-) in aqueous acidic medium (pH 4.8) resulted in three novel polyanions, [Sb(3)(A-α-XW(9)O(34))(2)](11-) (X = Si(IV) (1), Ge(IV) (2)) and [Sb(6)O(2)(A-PW(6)O(26))(A-α-PW(9)O(34))(2)](15-) (3), which were isolated as the hydrated potassium salts K(11)[Sb(3)(A-α-XW(9)O(34))(2)]·31H(2)O (X = Si(IV) (K-1), Ge(IV) (K-2)) and the mixed potassium-sodium salt K(14)Na[Sb(6)O(2)(A-PW(6)O(26))(A-α-PW(9)O(34))(2)]·61H(2)O (KNa-3) salts, respectively, and characterized by single-crystal X-ray diffraction, IR spectroscopy, as well as elemental and thermogravimetric analyses. The Sb(III)-containing polyanions 1-3 possess unique structural features, as they represent the first examples of sandwich-type POMs with trigonal-pyramidal Sb(III)O(3) linkers. The stability of 1-3 in aqueous media was investigated by multinuclear ((183)W, (31)P) NMR and UV-Vis spectroscopy.
Dalton Transactions 04/2012; 41(33):9914-21. · 3.84 Impact Factor
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ABSTRACT: The mixed-valence 24-vanadophosphate
[ { \textRu\textII3 (dmso)9 \textPV\textV11 \textV\textIV \textRu\textIII \textO37 \text(OH)3 }2 ]8 - {\left[ {{\left\{ {{\text{Ru}}^{{{\text{II}}}}_{3} (dmso)_{9} {\text{PV}}^{{\text{V}}}_{{11}} {\text{V}}^{{{\text{IV}}}} {\text{Ru}}^{{{\text{III}}}} {\text{O}}_{{37}} {\text{(OH)}}_{3} } \right\}}_{2} } \right]}^{{8 - }} (1) has been synthesized and characterized in the solid state by IR, magnetism, EPR, XPS, and elemental analysis. Single-crystal
X-ray analysis was carried out on
\textNa8 [ { \textRu\textII3 (dmso)9 \textPV\textV11 \textV\textIV \textRu\textIII \textO37 \text(OH)3 }2 ] 46\textH2 \textO {\text{Na}}_{8} {\left[ {{\left\{ {{\text{Ru}}^{{{\text{II}}}}_{3} (dmso)_{9} {\text{PV}}^{{\text{V}}}_{{11}} {\text{V}}^{{{\text{IV}}}} {\text{Ru}}^{{{\text{III}}}} {\text{O}}_{{37}} {\text{(OH)}}_{3} } \right\}}_{2} } \right]} \cdot 46{\text{H}}_{2} {\text{O}} (Na-1), which crystallizes in the triclinic system, space group P[`1] \hbox{P}\overline{1} , with a=17.168(3)Å, b=18.1971(14)Å, c=20.1422(13)Å, α=114.753(3)°, β=99.390(4)°, γ=95.124(4)°, and Z=2. Polyanion 1 has an unusual, open structure composed of 2 RuIIIO6 octahedra, 2 VIVO6 octahedra, 14 VVO5 square-pyramids, 8 VVO4 tetrahedra, and 2 PO4 tetrahedra which are all directly linked via edges and corners. The outer surface of 1 is decorated with six RuII(dmso)3 groups. XPS studies on Na-1 confirm the presence of 2 RuIII and 6 RuII as well as 22 VV and 2 VIV centers. Magnetic susceptibility data on Na-1 show that the VIV–RuIII pairs are coupled antiferromagnetically, with J
1=−13K and J
2∼−3K. We did not detect any peak in our EPR measurements on Na-1, thus supporting the conclusion that Na-1 is diamagnetic in its ground state.
Journal of Cluster Science 04/2012; 19(1):259-273. · 0.92 Impact Factor
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ABSTRACT: Wheely: For the first time and very unexpectedly, a rupture of the very stable {P(8)W(48)} wheel was observed in aqueous solution at pH 4 and 80 °C in the presence of Fe(III), Eu(III)/Gd(III), and H(2)O(2). This inorganic ring opening is unprecedented in polyoxometalate chemistry.
Chemistry 04/2012; 18(20):6163-6. · 5.93 Impact Factor
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ABSTRACT: Trapped in a noble cube: A novel family of noble metalates has been discovered in which a 3d metal ion M (M = Mn(II), Fe(III), Co(II), Cu(II), Zn(II)) is encapsulated by a 12 palladium-oxo cage {Pd(12)O(32)}, which is capped by eight phosphate groups. Such discrete nanocubes were further investigated by EPR spectroscopy, electrochemistry, and in homogeneous hydrogenation catalysis.
Chemistry 04/2012; 18(20):6167-71. · 5.93 Impact Factor
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ABSTRACT: Iron-substituted crown-type polyoxometalate (POM) [P(8)W(48)O(184)Fe(16)(OH)(28)(H(2)O)(4)](20-) has been successfully immobilized onto glassy carbon electrode surfaces by means of the layer-by-layer (LBL) technique employing the cationic redox active dye, methylene blue (MB). The constructed multilayers exhibit pH-dependent redox activity for both the anionic POM and the cationic dye moieties, which is in good agreement with their solution behavior. The films have been characterized by alternating current impedance, atomic force microscopy, and X-ray photoelectron spectroscopy, whereby the nature of the outer layer within the assemblies was found to have an effect upon the film's behavior. Preliminary investigations show that the POM dye-based films show electrocatalytic ability toward the reduction of hydrogen peroxide, however, only when there is an outer anionic POM layer.
Langmuir 02/2012; 28(12):5480-8. · 4.19 Impact Factor
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Masahiro Sadakane,
Sachie Moroi,
Yoshifumi Iimuro,
Natalya Izarova, Ulrich Kortz,
Shinjiro Hayakawa,
Kazuo Kato,
Shuhei Ogo,
Yusuke Ide,
Wataru Ueda,
Tsuneji Sano
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ABSTRACT: Ruthenium(III)-substituted α-Keggin-type silicotungstates with pyridine-based ligands, [SiW(11)O(39)Ru(III)(Py)](5-), (Py: pyridine (1), 4-pyridine-carboxylic acid (2), 4,4'-bipyridine (3), 4-pyridine-acetamide (4), and 4-pyridine-methanol (5)) were prepared by reacting [SiW(11)O(39)Ru(III)(H(2)O)](5-) with the pyridine derivatives in water at 80 °C and then isolated as their hydrated cesium salts. These compounds were characterized using cyclic voltammetry (CV), UV/Vis, IR, and (1)H NMR spectroscopy, elemental analysis, titration, and X-ray absorption near-edge structure (XANES) analysis (Ru K-edge and L(3)-edge). Single-crystal X-ray analysis of compounds 2, 3, and 4 revealed that Ru(III) was incorporated in the α-Keggin framework and was coordinated by pyridine derivatives through a Ru-N bond. In the solid state, compounds 2 and 3 formed a dimer through π-π interaction of the pyridine moieties, whereas they existed as monomers in solution. CV indicated that the incorporated Ru(III)-Py was reversibly oxidized into the Ru(IV)-Py derivative and reduced into the Ru(II)-Py derivative.
Chemistry - An Asian Journal 02/2012; 7(6):1331-9. · 4.50 Impact Factor
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ABSTRACT: Reaction of (C2H5)2SnCl2 with the trilacunary 9-tungstoarsenate(V) [A–a–AsW9O34]9- in aqueous pH 5 medium resulted in the diethyltin-containing polyanion [{Sn(C2H5)2}3(H2O)6(A–a–AsVW9O34)]3- (1), which crystallized as a hydrated guanidinium salt, [C(NH2)3]3[{Sn(C2H5)2}3(H2O)4(A–a–AsVW9O34)] 9H2O (1a). Polyanion 1 represents the first example of a diethyltin-containing polyanion. The diethyltin groups are bound to the trilacunary Keggin units via two Sn–O(W) bonds involving edge-shared WO6 octahedra. Each Sn atom also has two terminal, cis-related water ligands, and two terminal, trans-related ethyl groups. Multinuclear (1H, 13C, 119Sn, 183W) NMR spectrometry indicated that polyanion 1 is stable in solution. Compound 1a was structurally characterized in the solid state by single-crystal XRD, FT-IR, as well as thermogravimetric and elemental analyses. Single-crystal X-ray analysis showed that 1a crystallizes in the orthorhombic system, space group Pnma, with a = 23.5280(10) A ̊ , b = 15.5435(6) A ̊ , c = 18.6191(9) A ̊ , V = 6809.1(5) A ̊ 3 and Z = 4. The structure of 1a is an extended 2D assembly of individual polyanion units 1 linked via Sn–O(W) bridges.
Journal of Cluster Science 01/2012; · 0.92 Impact Factor
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ABSTRACT: Reaction of (C 2 H 5 ) 2 SnCl 2 with the trilacunary 9-tungstoarsenate(V) [ A–α– AsW 9 O 34 ] 9− in aqueous pH 5 medium resulted in the diethyltin-containing polyanion [Sn(C 2 H 5 ) 2 3 (H 2 O) 6 ( A–α– As V W 9 O 34 )] 3− ( 1 ), which crystallized as a hydrated guanidinium salt, [C(NH 2 ) 3 ] 3 [Sn(C 2 H 5 ) 2 3 (H 2 O) 4 ( A–α– As V W 9 O 34 )]·9H 2 O ( 1a ). Polyanion 1 represents the first example of a diethyltin-containing polyanion. The diethyltin groups are bound to the trilacunary Keggin units via two Sn–O(W) bonds involving edge-shared WO 6 octahedra. Each Sn atom also has two terminal, cis -related water ligands, and two terminal, trans -related ethyl groups. Multinuclear ( 1 H, 13 C, 119 Sn, 183 W) NMR spectrometry indicated that polyanion 1 is stable in solution. Compound 1a was structurally characterized in the solid state by single-crystal XRD, FT-IR, as well as thermogravimetric and elemental analyses. Single-crystal X-ray analysis showed that 1a crystallizes in the orthorhombic system, space group P nma , with a = 23.5280(10) Å, b = 15.5435(6) Å, c = 18.6191(9) Å, V = 6809.1(5) Å 3 and Z = 4. The structure of 1a is an extended 2D assembly of individual polyanion units 1 linked via Sn–O(W) bridges.
Journal of Cluster Science 01/2012; 23(3):939-951. · 0.92 Impact Factor
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ABSTRACT: Reaction of [MnIII8MnIV4O12(CH3COO)16(H2O)4] with [A-a-PW9O34]9 in a 1:2 molar ratio in aqueous, acidic medium resulted in the manganese(III)-containing, sandwich-type tungstophosphate [MnIII3(H2- O)5(A-a-PW9O34)2]9 (1). Polyanion 1 crystallizes as a mixed potassium/cesium/guanidinium salt in the triclinic space group P1, with cell parameters a = 13.1718(19) Å, b = 16.505(2) Å, c = 22.842(4) Å, a = 104.141(7)°, b = 106.267(8)°, c = 101.369(6)°, V = 4430.6(12) Å3, and Z = 2. The title polyanion com- prises two [A-a-PW9O34]9 Keggin fragments linked via three MnIII ions, two of which are 6-coordinated and one is 5-coordinated. Polyanion 1 was further characterized by IR, TGA, elemental analysis, magnetic measurements, and electrochemistry.
Polyhedron 01/2012; · 2.06 Impact Factor
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ABSTRACT: We have synthesized and structurally characterized three pyridylethylidene-functionalized diphosphonate-containing polyoxomolybdates, [{Mo(VI)O(3)}(2){Mo(V)(2)O(4)}{HO(3)PC(O)(CH(2)-3-C(5)NH(4))PO(3)}(2)](6-) (1), [{Mo(VI)(2)O(6)}(2){Mo(V)(2)O(4)}{O(3)PC(O)(CH(2)-3-C(5)NH(4))PO(3)}(2)](8-) (2), and [{Mo(V)(2)O(4)(H(2)O)}(4){O(3)PC(O)(CH(2)-3-C(5)NH(4))PO(3)}(4)](12-) (3). Polyanions 1-3 were prepared in a one-pot reaction of the dinuclear, dicationic {Mo(V)(2)O(4)(H(2)O)(6)}(2+) with 1-hydroxo-2-(3-pyridyl)ethylidenediphosphonate (Risedronic acid) in aqueous solution. Polyanions 1 and 2 are mixed-valent Mo(VI/V) species with open tetranuclear and hexanuclear structures, respectively, containing two diphosphonate groups. Polyanion 3 is a cyclic octanuclear structure based on four {Mo(V)(2)O(4)(H(2)O)} units and four diphosphonates. Polyanions 1 and 2 crystallized as guanidinium salts [C(NH(2))(3)](5)H[{Mo(VI)O(3)}(2){Mo(V)(2)O(4)}{HO(3)PC(O)(CH(2)-3-C(5)NH(4))PO(3)}(2)]·13H(2)O (1a) and [C(NH(2))(3)](6)H(2)[{Mo(VI)(2)O(6)}(2){Mo(V)(2)O(4)}{O(3)PC(O)(CH(2)-3-C(5)NH(4))PO(3)}(2)]·10H(2)O (2a), whereas polyanion 3 crystallized as a mixed sodium-guanidinium salt, Na(8)[C(NH(2))(3)](4)[{Mo(V)(2)O(4)(H(2)O)}(4){O(3)PC(O)(CH(2)-3-C(5)NH(4))PO(3)}(4)]·8H(2)O (3a). The compounds were characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric and elemental analyses. The formation of polyanions 1 and 3 is very sensitive to the pH value of the reaction solution, with exclusive formation of 1 above pH 7.4 and 3 below pH 6.6. Detailed solution studies by multinuclear NMR spectrometry were performed to study the equilibrium between these two compounds. Polyanion 2 was insoluble in all common solvents. Detailed computational studies on the solution phases of 1 and 3 indicated the stability of these polyanions in solution, in complete agreement with the experimental findings.
Inorganic Chemistry 11/2011; 50(22):11667-75. · 4.60 Impact Factor
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ABSTRACT: We have prepared the three novel Pd(II)-containing tungstophosphates [Pd(2)(α-PW(11)O(39)H(0.5))(2)](9-) and two structural isomers of [Pd(2)(α(2)-P(2)W(17)O(61)H(n))(2)]((16-2n)-) via simple synthetic procedures and characterized their potassium salts by single-crystal X-ray diffraction, elemental analysis, and IR and multinuclear ((31)P and (183)W) NMR spectroscopy. This study sheds light on the long-standing question about the nature and structure of the actual products formed in the reaction of Pd(II) ions with monolacunary Keggin-type [α-XW(11)O(39)](n-) and Wells-Dawson-type [α(2)-P(2)W(17)O(61)](10-) heteropolytungstates.
Inorganic Chemistry 09/2011; 50(20):10379-86. · 4.60 Impact Factor
