Coordination of Palladium(II) and Platinum(II) Complexes to One Vacant Site in an α-Keggin-Type Polyoxotungstate.

A palladium-platinum bimetal complex containing a mono-lacunary α-Keggin-type polyoxotungstate is demonstrated. The bimetallic complex Cs2.5{PdII(bpy)}0.25[α-PW11O39{PdII(bpy)}{cis-PtII(NH3)2}]·12H2O·2CH3CN (bpy = 2,2'-bipyridine) (PdPt) was synthesized by the reaction of Cs4.9K0.1[α-PW11O39{cis-PtII(NH3)2}]·10H2O (Pt1) with PdII(bpy)Cl2 in aqueous solution. The compound PdPt was characterized via elemental analysis, thermogravimetric/differential thermal analysis, and Fourier transform infrared, ultraviolet-visible, cold-spray ionization mass, and solution (1H, 13C, and 31P) nuclear magnetic resonance spectroscopies. The coordination of {cis-PtII(NH3)2} and {PdII(bpy)} moieties to the mono-vacant site of [PW11O39]7- resulted in an asymmetric, monomeric compound. A unique exchange reaction between the counter cation [PdII(bpy)]2+ and {cis-PtII(NH3)2} moiety in [α-PW11O39{PdII(bpy)}{cis-PtII(NH3)2}]3- in a dimethylsulfoxide solution was also observed.

Synthesis, X-ray Crystal Structure, and Photochromism of a Sandwich-Type Mono-Aluminum Complex Composed of Two Tri-Lacunary α-Dawson-Type Polyoxotungstates.

The synthesis and molecular structure of a dimeric, mono-aluminum complex composed of two tri-lacunary α-Dawson polyoxometalates, [H14Al(B-α-P2W15O56)2]7- (1), is described herein. The tetra-n-butylammonium salt of 1, [(n-C4H9)4N]7[H14Al(B-α-P2W15O56)2] (TBA-1) was prepared by passing an aqueous solution of K6[B-α-H3P2W15O59{Al(OH2)}3]⋅14H2O through an ion-exchange resin column (H+-form), followed by addition of tetra-n-butylammonium bromide. Analytically pure and colorless crystals of TBA-1 were obtained via vapor diffusion from acetonitrile/methanol at ~25 °C. Single-crystal X-ray structure analysis revealed that a six-coordinate aluminum ion was sandwiched between two tri-lacunary α-Dawson-type units, resulting in an overall C2h symmetry. The characterization of TBA-1 was accomplished by elemental analyses, thermogravimetric/differential thermal analyses, Fourier-transform infrared spectroscopy, and solution 31P nuclear magnetic resonance spectroscopy. The photochromic properties of TBA-1 were also characterized in methanol under light irradiation (λ = 365 nm and ≥400 nm).

Binary Nanoparticle Graphene Hybrid Structure-Based Highly Sensitive Biosensing Platform for Norovirus-Like Particle Detection.

Nanoparticle (NP)-decorated carbon nanotubes or graphenes (GRPs) have attracted attention because of their synergic properties such as enhanced electrical conductivity, magneto-optical effect, and plasmon resonance energy transfer. These hybrid carbon nanomaterials are widely used in sensing platforms to monitor target biomolecules, gases, and chemicals. In this study, binary nanoparticles, specifically gold (Au)/magnetic nanoparticle (MNP)-decorated graphenes (GRPs), were applied in a virus-sensing platform. This hybrid material exhibited multiple functionalities, including magnetic, plasmonic, and enhanced electrical properties. The Au/MNP-GRPs were synthesized in two steps at room temperature under mild conditions and magnetically deposited on a Pt-interdigitated electrode as electrical-sensing channels. After deposition onto the electrode, the surface of Au/MNP-GRPs was conjugated with norovirus antibody to produce a norovirus-like particle (NoV-LP)-sensing platform. NoV-LPs were successfully detected by the hybrid nanomaterial-sensing platform, exhibiting high sensitivity and specificity in a concentration range from 0.01 pg to 1 ng. In this case, the limit of detection was calculated as 1.16 pg/mL. Thus, the binary nanoparticle-decorated graphene shows excellent potential as an electrical-sensing platform for biomolecules.

Syntheses and molecular structures of monomeric and hydrogen-bonded dimeric Dawson-type trialuminum-substituted polyoxotungstates derived under acidic and basic conditions.

The syntheses and molecular structures of the two types of α-Dawson-type trialuminum-substituted polyoxometalates, [B-α-H3P2W15O59{Al(OH2)}3](6-) (1) and [B-α-H3P2W15O59{Al(OH)}2{Al(OH2)}]2(16-) (2), are described herein. The potassium and cesium salts of 1, K6[B-α-H3P2W15O59{Al(OH2)}3]·14H2O (K-1), and Cs6[B-α-H3P2W15O59{Al(OH2)}3]·13H2O (Cs-1) were formed by a stoichiometric reaction in water of trilacunary α-Dawson polyoxotungstate with aluminum nitrate under acidic conditions (pH ∼3). The potassium/sodium and tetramethylammonium/sodium salts of 2, K14Na2[B-α-H3P2W15O59{Al(OH)}2{Al(OH2)}]2·30H2O (KNa-2) and [(CH3)4N]14Na2[B-α-H3P2W15O59{Al(OH)}2{Al(OH2)}]2·39H2O (TMANa-2) were obtained under basic conditions (pH ∼9). These compounds were characterized by X-ray structure analyses, elemental analyses, thermogravimetric/differential thermal analyses, Fourier transform infrared, and solution (31)P, (27)Al, and (183)W NMR spectroscopy. The polyoxoanion 1 is a monomeric, α-Dawson-type structure, resulting in an overall C3v symmetry, while the polyoxoanion 2 is a hydrogen-bonded dimeric structure, resulting in an overall S3 symmetry in the solid state. The pH dependence of polyoxoanions 1 and 2 in aqueous solution was also investigated by (31)P NMR spectroscopy.

Synthesis, molecular structure, and stability of a zirconocene derivative with α-Keggin mono-aluminum-substituted polyoxotungstate.

The synthesis and crystal structure of a zirconocene derivative with α-Keggin mono-aluminum-substituted polyoxotungstate, [α-PW(11)Al(OH)O(39)ZrCp(2)](2)(6-) (Cp = C(5)H(5)(-)) (1), which was obtained by the reaction of α-Keggin mono-aluminum-substituted polyoxotungstate with a biscyclopentadienylzirconium(IV) complex, is described herein. Analytically pure, homogeneous, yellow crystals of the tetra-n-butylammonium salt of polyoxoanion 1, [(n-C(4)H(9))(4)N](6)[α-PW(11)Al(OH)O(39)ZrCp(2)](2) (TBA-1), were obtained from the ca. 1 : 1 reaction of [(n-C(4)H(9))(4)N](4)[α-PW(11){Al(OH(2))}O(39)] with Cp(2)Zr(OTf)(2)·THF (OTf = O(3)SCF(3)(-)) in acetonitrile solution under an argon atmosphere, followed by precipitation from water and crystallization from acetonitrile. TBA-1 was characterized based on X-ray structure analysis, elemental analysis, thermogravimetric/differential thermal analysis (TG/DTA), Fourier transform infrared (FTIR), and solution ((31)P, (27)Al, (19)F, (1)H, and (13)C) nuclear magnetic resonance (NMR) spectroscopy. Single-crystal X-ray structure analysis revealed that the two {PW(11)AlO(40)} units are bridged by two "bent sandwich" Cp(2)Zr(2+) fragments with C(2) symmetry. Each zirconium center was bound to a terminal oxygen atom of the aluminum and tungsten sites and an edge-sharing oxygen atom at the Al-O-W linkage. Further, the stability towards water was investigated by NMR ((31)P, (1)H, and (13)C) and FTIR spectroscopy. The η(5)-cyclopentadienylzirconium fragments were not eliminated from the surface of [α-PW(11){Al(OH(2))}O(39)](4-) even after 24 h exposure to 50 equiv. of water.

Diplatinum(II)-coordinated polyoxotungstate: synthesis, molecular structure, and photocatalytic performance for hydrogen evolution from water under visible-light irradiation.

The synthesis and molecular structure of a monomeric diplatinum(II) complex composed of mono-lacunary α-Keggin polyoxometalate is described. The polyoxometalate, Cs(3)[α-PW(11)O(39){cis-Pt(NH(3))(2)}(2)]·8H(2)O (Cs-1), afforded by a stoichiometric reaction of mono-lacunary Keggin polyoxotungstate with cis-diamminedichloroplatinum(ii) in water, followed by crystallization from water, was obtained as analytically pure, homogeneous, yellow crystals. The compound Cs-1 was characterized by elemental analysis, thermogravimetric/differential thermal analysis (TG/DTA), Fourier transform infrared (FTIR) and UV-visible spectroscopy, solution (1)H and (31)P nuclear magnetic resonance (NMR), and X-ray crystallography. The single-crystal X-ray structure analysis revealed that the two cis-platinum(ii) moieties, [cis-Pt(NH(3))(2)](2+), were coordinated each to two oxygen atoms in a mono-vacant site of [α-PW(11)O(39)](7-) with asymmetric configuration, resulting in an overall C(1) symmetry. Furthermore, hydrogen evolution from an EDTA·2Na (ethylenediamine tetraacetic acid disodium salt) aqueous solution under visible-light irradiation (≥400 nm) was achieved by using polyoxoanion 1 and titanium dioxide.

A sandwich-type aluminium complex composed of tri-lacunary Keggin-type polyoxotungstate: synthesis and X-ray crystal structure of [(A-PW9O34)2{W(OH)(OH2)}{Al(OH)(OH2)}{Al(µ-OH)(OH2)2}2]7-.

The synthesis and molecular structure of a dimeric aluminium complex composed of tri-lacunary α-Keggin polyoxometalate is described. The polyoxometalate, K(6)Na[(A-PW(9)O(34))(2){W(OH)(OH(2))}{Al(OH)(OH(2))}{Al(µ-OH)(OH(2))(2)}(2)]·19H(2)O (KNa-1), afforded by the reaction in water of a tri-lacunary Keggin polyoxotungstate with excess aluminium nitrate, followed by crystallization from water, was obtained as analytically pure, homogeneous, colorless crystals. The compound KNa-1 was characterized by elemental analysis, TG/DTA, FT-IR, solution NMR ((31)P, (27)Al, and (183)W), and X-ray crystallography. The single-crystal X-ray structure analysis revealed that two 6-coordinate aluminium ions linked with two bridging hydroxyl groups and four water molecules, i.e., [Al(III)(2)(µ-OH)(2)(OH(2))(4)](4+); a unit of a 6-coordinate tungsten ion linked with a hydroxyl group and a water molecule, i.e., [W(OH)(OH(2))](5+); a unit of a 6-coordinate aluminium ion linked with a hydroxyl group and a water molecule, i.e., [Al(OH)(OH(2))](2+), were sandwiched between two tri-lacunary α-Keggin polyoxotungstates, resulting in an overall C(s) symmetry.

Syntheses and X-ray crystal structures of zirconium(IV) and hafnium(IV) complexes containing monovacant wells-Dawson and Keggin polyoxotungstates.

The syntheses and crystal structures of a series of zirconium(IV) and hafnium(IV) complexes with Dawson monovacant phosphotungstate [alpha2-P2W17O61](10-) and in situ-generated Keggin monovacant phosphotungstate [alpha-PW11O39](7-), which was obtained by a reaction of [alpha-PW12O40](3-) with Na2CO3, are described. K15H[Zr(alpha2-P2W17O61)2].25H2O (K-1), K16[Hf(alpha2-P2W17O61)2].19H2O (K-2), (Et2NH2)10[Zr(alpha-PW11O39)2].7H2O (Et2NH2-3), and (Et2NH2)10[Hf(alpha-PW11O39)2].2H2O (Et2NH2-4), being afforded by reactions in aqueous solutions of monolacunary Dawson and Keggin polyoxotungstates with ZrCl2O.8H2O and HfCl2O.8H2O followed by exchanging countercations, were obtained as analytically pure, homogeneous colorless crystals. Single-crystal X-ray structure analyses revealed that the Zr(IV) and Hf(IV) ions are in a square antiprismatic coordination environment with eight oxygen atoms, four of them being provided from each of the two monovacant polyanion ligands. Although the total molecular shapes and the 8-coordinate zirconium and hafnium centers of complexes 1-4 are identical, the bonding modes (bond lengths and bond angles) around the zirconium(IV) and hafnium(IV) centers were dependent on the monovacant structures of the polyanion ligands. Additionally, the characterization of complexes 1-4 was accomplished by elemental analysis, TG/DTA, FTIR, and solution (31P and 183W) NMR spectroscopy.

Discovery and development of microporous metal carboxylates.

We have found a form of copper(II) terephthalate that occluded an enormous amount of gases such as N2, Ar, O2, and Xe. Copper(II) terephthalate is the first metal complex found capable of adsorbing gases. This complex has opened a new field of adsorbent chemistry and is recognized as a leader in the construction of microporous metal complexes. In extending the route for the synthesis of microporous complexes, we obtained many new porous materials that are widely recognized as useful materials for applications in areas such as gas storage, molecular sieves, catalysis, inclusion complexes, and surface science.

Tetrameric, trititanium(IV)-substituted polyoxotungstates with an alpha-Dawson substructure as soluble metal-oxide analogues: molecular structure of the giant "tetrapod" [(alpha-1,2,3-P2W15Ti3O62)4[mu3-Ti(OH)3]4Cl]45-.

The preparation and structural characterization of the novel polyoxoanion [(alpha-1,2,3-P(2)W(15)Ti(3)O(62))(4)[mu(3)-Ti(OH)(3)](4)Cl](45-) (1 a; abbreviated to [TiO(6)](16); FW approximately 16 000) which consists of four tri-Ti(IV)-1,2,3-substituted alpha-Dawson substructures, four Ti(OH)(3) bridging groups, and one encapsulated Cl(-) ion, are described. A water-soluble, all-inorganic composition compound of the tetrameric Ti-O-Ti-bridged anhydride form, Na(x)H(45-x)[1 a].y H(2)O (1; x=16-19, y=60-70), which was afforded by the reaction of the tri-lacunary Dawson polyoxotungstate Na(12)[B-alpha-P(2)W(15)O(56)].19 H(2)O with an excess of TiCl(4) in aqueous solution, was obtained as analytically pure, homogeneous colorless crystals. Single-crystal X-ray structure analysis revealed that 1 a was an inorganic, giant "tetrapod"-shaped molecule (inscribed to a sphere with a diameter of approximately 32 A) with approximately T(d) symmetry, in which the 16 edge- and/or corner-shared TiO(6) octahedra were contained. This number of TiO(6) octahedra was larger than that found in other titanium(IV)-substituted polyoxotungstates. Complex 1 was characterized by complete elemental analysis, TG/DTA, FTIR, UV/Vis absorption, and solution ((31)P and (183)W) NMR spectroscopy. The longest wavelength band in the UV/Vis absorption spectra of 1 in water was attributed to the O-->Ti(IV) ligand-to-metal charge-transfer (LMCT) transition: the wavelength of the LMCT band increased linearly as the number of TiO(6) octahedra contained in the Keggin and Dawson polyoxoanions increased. The Ti(n) chromophores formed in the Keggin and Dawson polyoxotungstates are water-soluble analogues of solid TiO(2) or SrTiO(3) as light-semiconductors and photocatalysts.