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41.
The 48-FeIII-containing 96-tungsto-16-phosphate, [FeIII48(OH)76(H2O)16(HP2W12O48)8]36− ( Fe48 ), has been synthesized and structurally characterized. This polyanion comprises eight equivalent {FeIII6P2W12} units that are linked in an end-on fashion forming a macrocyclic assembly that contains more iron centers than any other polyoxometalate (POM) known to date. The novel Fe48 was synthesized by a simple one-pot reaction of an {Fe22} coordination complex with the hexalacunary {P2W12} POM precursor in water. The title polyanion was characterized by single-crystal XRD, FTIR, TGA, magnetic and electrochemical studies.  相似文献   
42.
43.
Pyrogallol[4]arenes form stable hydrogen-bonded nanocapsules that have unique properties that may make them suitable for diverse applications, such as catalysts and molecular transporters. Little is known about the behavior of the interior of these new materials in solution, and by using the solvent-dependent properties of 1-(9-anthryl)-3-(4-dimethylaniline) propane (ADMA), the inner phase properties of the hexamers are investigated. Steady-state and dynamic spectrofluorometric results are in agreement, are consistent with solid-state studies, and indicate that the majority of ADMA is sequestered in an extended conformation with the crystallization solvent. The conformational flexibility of ADMA is attributed to lower capsule occupancies ( approximately 50%, i.e., 1 molecule per 2 capsules, one occupied and one empty) relative to our previous study with pyrene butyric acid (occupancy of 150%, i.e., 1.5 molecules per capsule) in which the probe was restricted within a nanocapsule. The nature of the encapsulated ADMA complexes are found to change with time, as there is either fluorophore leaching from the capsule or endo-exo-capsule solvent exchange. However, the choice of crystallizing solvent (ethyl acetate or acetonitrile) and PgC(n) alkyl tail (C(6) or C(10)) does not influence experimental outcomes. These research findings give a better understanding of the encapsulation versatility of these unique supramolecular assemblies and the protective nanopockets that can exist for guest molecules.  相似文献   
44.
The three novel, discrete palladium(II)‐oxo clusters [CaPd12O8(PhAsO3)8]6? ( CaPd12 ), [SrPd12O6(OH)3(PhAsO3)6(OAc)3]4? ( SrPd12 ), and [BaPd15O10(PhAsO3)10]8? ( BaPd15 ) encapsulating alkaline earth metal ions were prepared and fully characterized by a multitude of solution and solid‐state physicochemical techniques. We have discovered a structure‐directing template effect induced by the respective size of the alkaline earth guest ion, which determines the detailed condensation arrangement of the peripheral PdII‐oxo shell. The unprecedented SrPd12 with an open‐shell type structure is of particular importance and reflects a successful strategy for deliberate design of new structural classes of polyoxo‐noble‐metalates. Furthermore, the unusual acetate–water ligand exchange phenomenon renders SrPd12 as a promising candidate for noble‐metal‐based catalysis.  相似文献   
45.
46.
We present an ensemble of formulae for the calculation of the Glauber correction to incoherent production on deuterons. The formulae are written in terms of phases, slopes and integrated cross sections and both the diffractive and non-diffractive case are considered. It is shown in the case K+ → K0π+, that only if the analysis is done in such a way that the final set of states is complete, is there agreement between theory and experiment.  相似文献   
47.
We have synthesized and structurally characterized the unprecedented peroxo-zirconium(IV) containing [Zr6(O2)6(OH)6(gamma-SiW10O36)3]18- (1). Polyanion 1 comprises a cyclic 6-peroxo-6-zirconium core stabilized by three decatungstosilicate units. We have also prepared the isostructural hafnium(IV) analogue [Hf6(O2)6(OH)6(gamma-SiW10O36)3]18- (2). We investigated the acid/base and redox properties of 1 by UV-vis spectroscopy and electrochemistry studies. Polyanion 1 represents the first structurally characterized Zr-peroxo POM with side-on, bridging peroxo units. The simple, one-pot synthesis of 1 and 2 involving dropwise addition of aqueous hydrogen peroxide could represent a general procedure for incorporating peroxo groups into a large variety of transition metal and lanthanide containing POMs.  相似文献   
48.
The 36-NiII-containing 54-tungsto-6-silicate, [Ni36(OH)18(H2O)36(SiW9O34)6]6− ( Ni36 ) was synthesized by a simple one-pot reaction of the Ni2-pivalate complex [Ni2(μ-OH2)(O2CCMe3)4(HO2CCMe3)4] with the trilacunary [SiW9O34]10− polyanion precursor in water and structurally characterized by a multitude of physicochemical techniques including single-crystal XRD, FTIR, TGA, elemental analysis, magnetic and electrochemical studies. Polyanion Ni36 comprises six equivalent {NiII6SiW9} units which are linked by Ni−O−W bridges forming a macrocyclic assembly. Magnetic studies demonstrate that the {Ni6} building blocks in Ni36 remain magnetically intact while forming a hexagonal ring with antiferromagnetic exchange interactions between adjacent {Ni6} units. Electrochemical studies indicate that the first reduction is reversible and associated with the WVI/V couple, whereas the second reduction is irreversible attributed to the NiII/0 couple.  相似文献   
49.
The sequestration of carbon dioxide fumes from oxyfuel combustion is used to reduce significantly the carbon dioxide emissions from coal-fired power plants. Impurities like nitric oxide, present in the fumes, can cause technical difficulties during the capture, the treatment, the transport, and the storage steps of the CO2 fumes. The purpose of this study is to better understand the oxidation of nitric oxide under pressure in the presence of carbon dioxide and in the experimental condition of flue gas treatment. This reaction is known to be a third-order reaction, two order in nitric oxide and first order in oxygen. To examine the effect of the temperature, the pressure and the volume fraction of oxygen on the rate constant of oxidation, k1, an autoclave is used. The first experiment studies the influence of the temperature between 288 and 323 K. The results found are in the form of an Arrhenius-type equation: k1 = 810 exp(620/T) and are in agreement with the literature. Carbon dioxide does not seem to have an influence on the rate constant, whereas our experimental measurements indicate an influence of the volume fraction of oxygen. The rate constant decreases when the oxygen volume fraction increases by up to 10%. Then the rate constant remains constant. This observation allows us to conclude that the mechanism involving the mechanism with a dimer of NO as an intermediate is more likely to be the mechanism involved in the nitric oxide oxidation in our experimental conditions: high pressure and ambient temperature. The rate constant k2, k–2, and k3 were also estimated in these conditions.  相似文献   
50.
A family of three sandwich‐type, phenylantimony(III)‐containing tungstoarsenates(III), [(PhSbIII){Na(H2O)}AsIII2W19O67(H2O)]11? ( 1 ), [(PhSbIII)2AsIII2W19O67(H2O)]10? ( 2 ), and [(PhSbIII)3(B‐α‐AsIIIW9O33)2]12? ( 3 ), have been synthesized by one‐pot procedures and isolated as hydrated alkali metal salts, Cs3K3.5Na4.5[(PhSbIII){Na(H2O)}AsIII2W19O67(H2O)]?41H2O ( CsKNa ‐ 1 ), Cs4.5K5.5[(PhSbIII)2AsIII2W19O67(H2O)]?35H2O ( CsK‐2 ), and Cs4.5Na7.5[(PhSbIII)3(B‐α‐AsIIIW9O33)2]?42H2O ( CsNa ‐ 3 ). The number of incorporated {PhSbIII} units could be selectively tuned from one to three by careful control of the reaction parameters. The three compounds were characterized in the solid state by single‐crystal XRD, IR spectroscopy, and thermogravimetric analysis. The aqueous solution stability of sandwich polyanions 1 – 3 was also studied by multinuclear (1H, 13C, 183W) NMR spectroscopy. Effective inhibitory activity against six different kinds of bacteria was identified for all three polyanions, for which the activity increased with the number of incorporated {PhSbIII} groups.  相似文献   
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