Bis[1,1'-N,N'-(2-picolyl)aminomethyl]ferrocene as a redox sensor for transition metal ions

The compound bis[1,1'-N,N'-(2-picolyl)aminomethyl]ferrocene, L(1), was synthesized. The protonation constants of this ligand and the stability constants of its complexes with Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+) were determined in aqueous solution by potentiometric methods at 25 degrees C and at ionic strength 0.10 mol dm(-3) in KNO(3). The compound L(1) forms only 1:1 (M:L) complexes with Pb(2+) and Cd(2+) while with Ni(2+) and Cu(2+) species of 2 [ratio] 1 ratio were also found. The complexing behaviour of L(1) is regulated by the constraint imposed by the ferrocene in its backbone, leading to lower values of stability constants for complexes of the divalent first row transition metals when compared with related ligands. However, the differences in stability are smaller for the larger metal ions. The structure of the copper complex with L(1) was determined by single-crystal X-ray diffraction and shows that a species of 2:2 ratio is formed. The two copper centres display distorted octahedral geometries and are linked through the two L(1) bridges at a long distance of 8.781(10) Angstrom. The electrochemical behaviour of L(1) was studied in the presence of Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+), showing that upon complexation the ferrocene-ferrocenium half-wave potential shifts anodically in relation to that of the free ligand. The maximum electrochemical shift ([capital Delta]E(1/2)) of 268 mV was found in the presence of Pb(2+), followed by Cu(2+)(218 mV), Ni(2+)(152 mV), Zn(2+)(111 mV) and Cd(2+)(110 mV). Moreover, L(1) is able to electrochemically and selectively sense Cu(2+) in the presence of a large excess of the other transition metal cations studied.     

Protolytic reactions of 3,3'-dimethylnaphthidine and 3,3'-dimethoxybenzidine

The dissociation constants of diprotonated 3,3'-dimethylnaphthidine (DMN) and 3,3'-dimethoxybenzidine (DMB) have been determined spectrophotometrically. They are: pK(a1) = 2.62 +/- 0.03, pK(a2) = 3.33 +/- 0.09 for DMN: pK(a1) = 2.83 +/- 0.07, pK(a2) = 4.05 +/- 0.12 for DMB. The molar absorptivities (l.mole(-1).cm(-1)) of all forms of the indicators have been also determined: epsilon(B) = 1.68 x 10(4), epsilon(BH(+)) = 9.34 x 10(3), epsilon(BH(2+)(2)) = 1.80 x 10(3) at 300 nm for DMB; epsilon(B) = 7.33 x 10(3), epsilon(BH(+)) = 3.73 x 10(3), epsilon(BH(2+)(2)) = 0 at 330 nm for DMN.     

Hydration of gaseous copper dications probed by IR action spectroscopy

Clusters of Cu (2+)(H 2O) n , n = 6-12, formed by electrospray ionization, are investigated using infrared photodissociation spectroscopy, blackbody infrared radiative dissociation (BIRD), and density functional theory of select clusters. At 298 K, the BIRD rate constants increase with increasing cluster size for n >or= 8, but the trend reverses for the smaller clusters where Cu (2+)(H 2O) 6 is less stable than Cu (2+)(H 2O) 8. This trend in stability is consistent with a change in fragmentation pathway from loss of a water molecule for clusters with n >or= 9 to loss of hydrated protonated water clusters and the formation of the corresponding singly charged hydrated metal hydroxide for n 相似文献   

Ion flotation of rhodium(III) and palladium(II) with anionic surfactants

The ion flotation of rhodium(III) and palladium(II) with some anionic surfactants has been investigated. Two flotation procedures are proposed for the separation of some platinum metals, based on differences in the kinetic properties of the chloro-complexes of rhodium(III), palladium(II) and platinum(IV). The first involves the selective flotation of Rh(H(2)O)(3+)(6) from PdCl(2-)(4) and PtCl(2-)(6) in dilute hydrochloric acid with sodium dodecylbenzenesulfonate (SDBS). After precipitation of the hydroxide and redissolution in dilute acid, the Rh(III) is converted into Rh(H(2)O)(3+)(6), Pd(II) and Pt(IV) remaining as PdCl(2-)(4) and PtCl(2-)(6) respectively, and separation is achieved by floating the Rh(H(2)O)(3+)(6) with SDBS. The second is for separation of Pd(II). Prior to flotation, the solution of PdCl(2-)(4) and PtCl(2-)(6) is heated with ammonium acetate to convert PdCl(2-)(4) into Pd(NH(3))(2+)(4). The chloro-complex of Pt(IV) is unaffected. The complex cation, Pd(NH(3))(2+)(4), is then selectively floated with SDBS. The procedures are fast, simple and do not require expensive reagents and apparatus.     

Construction and analytical applications of an extractive electrode sensitive to mercury(I)

The construction and characteristics of a new type of extractive electrode sensitive to Hg(2+)(2) are described. The performance of the electrode is compared with that of an ion-selective electrode with mercurous dithizonate as the active substance. The Hg(2+)(2) -extractive electrode contains Pd(HDz)(2) in its membrane. Its stability and sensitivity are remarkable. It has been used as indicator electrode for the titration of halides alone and in mixtures, and for determination of mercury(I), mercury(II), silver, and of substances containing or reacting with mercury. The basis of the electrode response is discussed.     

Dual function of rare earth doped nano Bi(2)O(3): white light emission and photocatalytic properties

Undoped Bi(2)O(3) and single and double doped Bi(2)O(3)?:?M (where M = Tb(3+) and Eu(3+)) nanophosphors were synthesized through a simple sonochemical process and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), EDS, diffuse reflectance (DRS) and photoluminescence (PL) spectrophotometry. The TEM micrographs show that resultant nanoparticles have a rod-like shape. Energy transfer was observed from host to the dopant ions. Characteristic green emissions from Tb(3+) ions and red emissions from Eu(3+) ions were observed. Interestingly, the Commission International de l'Eclairage (CIE) coordinates of the double doped Bi(2)O(3)?:?Eu(3+)(0.8%)?:?Tb(3+)(1.2%) nanorods lie in the white light region of the chromaticity diagram and it has a quantum efficiency of 51%. The undoped Bi(2)O(3) showed a band gap of 3.98 eV which is red shifted to 3.81eV in the case of double doped Bi(2)O(3)?:?Eu(3+)(0.8%)?:?Tb(3+)(1.2%) nanorods. The photocatalytic activities of undoped nano Bi(2)O(3) and double doped nano Bi(2)O(3)?:?Eu(3+)(0.8%)?:?Tb(3+)(1.2%) were evaluated for the degradation of Rhodamine B under UV irradiation of 310 nm. The results showed that Bi(2)O(3)?:?Eu(3+)(0.8%)?:?Tb(3+)(1.2%) had better photocatalytic activity compared to undoped nano Bi(2)O(3). The evolution of CO(2) was realized and these results indicated the continuous mineralization of rhodamine B during the photocatalytic process. Thus double doped Bi(2)O(3)?:?Eu(3+)(0.8%)?:?Tb(3+)(1.2%) nanorods can be termed as a bifunctional material exhibiting both photocatalytic properties and white light emission.     

Ternary rare earth osmium aluminides R(7+)(x)Os(12)Al(61+)(y) belonging to a structural family with layered topology

The 10 intermetallic compounds R(7+)(x)Os(12)Al(61+)(y) (R = Y, Nd, Sm, Gd-Tm) were prepared by arc-melting of the elemental components. They crystallize with a hexagonal structure very similar to that of Y(7.28)Re(12)Al(61.38). The structure was determined from four-circle diffractometer data of Y(7+)(x)Os(12)Al(61+)(y): P6(3)/mcm, a = 1301.5(2) pm, c = 903.0(2) pm, Z =1. Four atomic sites, all located on the 6(3) axis, show fractional occupancy, resulting in the composition Y(7.86(1))Os(12)Al(61.51(4)), corresponding to the Pearson symbol hP90-8.63. The structure may be viewed as consisting of alternating atomic layers of two kinds, although chemical bonding within and between the layers is of similar character as can be judged from the near-neighbor environments, where all of the 11 atomic sites have high coordination numbers. One kind of layers (A). is relatively loosely packed and contains the yttrium and some aluminum atoms. The other kind (B). consists of the osmium and the remaining aluminum atoms in a nearly hexagonal close-packed arrangement. These layers are stacked in the sequence ABAB. A similar building principle has recently been recognized for several other structures of ternary intermetallic compounds of rare earth and transition metals with a high content of aluminum or gallium, where the structures of CeOsGa(4), Ho(3)Ru(4)Ga(15), and Y(2)Pt(6)Al(15) are the most recent examples. This structural family is briefly reviewed. The cell volume of Yb(7+)(x)Os(12)Al(61+)(y) indicates a mixed or intermediate valence character +2/+3 for the ytterbium atoms of this compound.     

Two-dimensional molecular ordering of Os(II) complexes in organo-clay hybrid ultrathin films

An ordered structure of [OsL(3)](2+)(L = 2, 2'-bipyridine or 1, 10-phenanthroline) layer in an ultrathin film composed of the complex cations, clay nanosheets and alkylammonium cations is reported on the basis of its in-plane X-ray diffraction and polarized electronic spectral data.     

Dinuclear Zn2+ complexes in the hydrolysis of the phosphodiester linkage in a diribonucleoside monophosphate diester

Dizinc complexes that were formed from 2:1 mixtures of Zn(NO3)2 and dinucleating ligands TPHP (1), TPmX (2) or TPpX (3) in aqueous solutions efficiently hydrolyzed diribonucleoside monophosphate diesters (NpN) under mild conditions. The dinucleating ligand affected the structure of the aquo-hydroxo-dizinc core, resulting in different characteristics in the catalytic activities towards NpN cleavage. The pH-rate profile of ApA cleavage in the presence of (Zn2+)(2)-1 was sigmoidal, whereas those of (Zn2+)(2)-2 and (Zn2+)(2)-3 were bell-shaped. The pH titration study indicated that (Zn2+)(2)-1 dissociates only one aquo proton (up to pH 12), whereas (Zn2+)(2)-2 dissociates three aquo protons (up to pH 10.7). The observed differences in the pH-rate profile are attributable to the various distributions of the monohydroxo-dizinc species, which are responsible for NpN cleavage. As compared to that using (Zn2+)(2)-1, the NpN cleavage using (Zn2+)(2)-2 showed a greater rate constant, with a higher product ratio of 3'-NMP/2'-NMP. The saturation behaviors of the rate, with regard to the concentration of NpN, were analyzed by Michaelis-Menten type kinetics. Although the binding of (Zn2+)(2)-2 to ApA was weaker than that of (Zn2+)(2)-1, (Zn2+)(2)-2 showed a greater kcat value than (Zn2+)(2)-1, resulting in higher ApA cleavage activity of the former.     

Stability and distribution studies on Sn(IV) and Cr(III) arsenophosphates: Separations of metal ions

The stability of tin(IV) and chromium(III) arsenophosphates in mineral acids and sodium hydroxide has been investigated. Structures for the two compounds are proposed, based on the results of thermogravimetric analysis, K(d) values for metal ions on these two compounds have been determined and separations of UO(2+)(2)-Th(4+), UO(2+)(2)-Zr(4+) and Na(+)-K(+) achieved.     

Use of chromium ferrocyanide membrane electrode in the potentiometric titration of ferrocyanide with metal ions

Membranes based on the inorganic ion-exchanger chromium ferrocyanide have been prepared, which exhibit linear response to ferrocyanide over the concentration range 10(-1)-10(-4)M. Although the electrode is not very specific for ferrocyanide, it can be used for potentiometric titration of metal ions with ferrocyanide ion or vice versa. Hg(2+), Th(6+), UO(2+)(2), Pb(2+), Cu(2+) and Zn(2+) have been determined in this way.     

Bimetallic reactivity. One-site addition two-metal oxidation reaction of dioxygen with a bimetallic dicobalt(II) complex bearing five- and six-coordinate sites

The di-Co(2+) complex, [Co(2+)(mu-OH)(oxapyme)Co(2+)(H(2)O)](+), contains an unsymmetrical binucleating ligand (oxapyme) which provides five- and six-coordinate metal sites when a hydroxide bridge is introduced. This complex absorbs 1 equiv of O(2) irreversibly in solution, producing an unstable di-Co(3+) oxygenated product. The oxygenated product has been studied at low temperatures, where its electronic absorption and (1)H NMR spectra were recorded. It is probable that the oxygenation reaction involves a one-site addition two-metal oxidation reaction to produce an end-on-bonded peroxide ligand at the available coordination site, giving the complex [Co(3+)(mu-OH)(oxapyme)Co(3+)(mu(1)-O(2))](+). Addition of 1 equiv of HClO(4) to this oxygenation product gives a stable peroxide complex, [Co(3+)(mu,eta(1):eta(2)-O(2))(oxapyme)Co(3+)](2+), where one of the oxygen atoms bridges the two metals and is sideways bonded to one of the metals. The formation of this stable complex involves expulsion of the OH(-) bridge. Addition of NO(2)(-) to the sideways-bonded peroxide complex leads to the formation of another stable complex, [Co(3+)(mu,eta(1):eta(1)-O(2))(oxapyme)Co(3+)(NO(2))](+), where the peroxide forms a classic di-end-on bridge to the two metals. Both of these complexes have been fully characterized. Addition of acid to this second stable dioxygen complex leads to the release of HNO(2) and the formation of the mu,eta(1):eta(2) sideways-bonded peroxide complex.     

Modeling of crystallization process in confined melt of sulfuric acid catalyst

Metropolis Monte Carlo technique has been applied to simulate the crystallization process in the melt of vanadium sulfuric acid supported catalysts. The melt is a lattice binary compound consisting of (V4+)(2) and (V5+)(2) binuclear complexes (dimers) confined by pore walls of cylindrical or slitlike shape. It has been shown that the crystallization process retards significantly as the pore size decreases. This result is in good agreement with the experimental data obtained earlier. The effect of the energy properties of pore walls (attractive, repulsive, or inert) on the crystallization features has been studied as well.     

Molecular-dynamics simulations of alkaline-earth metal cations in water by atom-bond electronegativity equalization method fused into molecular mechanics

Intermolecular potential for alkaline-earth metal (Be(2+), Mg(2+), and Ca(2+)) cations in water has been derived using the atom-bond electronegativity equalization method fused into molecular mechanics (ABEEM/MM), and it is consistent with what was previously applied to the hydration study of the monovalent cations. Parameters for the effective interaction between a cation and a water molecule were determined, reproducing the ab initio results. The static, dynamic, and thermodynamic properties of Be(2+)(aq), Mg(2+)(aq), and Ca(2+)(aq) were studied using these potential parameters. Be(2+) requires a more complicated form of the potential function than Mg(2+) and Ca(2+) in order to obtain better fits. Strong influences of the twofold charged cations on the structures of the hydration shells and some other properties of aqueous ionic solutions are discussed and compared with the results of a previous study of monovalent cations in water. At the same time, comparative study of the hydration properties of each cation is also discussed. This work demonstrates that ABEEM/MM provides a useful tool in the exploration of the hydration of double-charged cations in water.     

Billion-fold acceleration of the methanolysis of paraoxon promoted by La(OTf)3 in methanol

The methanolysis of the insecticide paraoxon (2) was investigated in methanol solution containing varying [La(OTf)(3)] (OTf = (-)OS(O)(2)CF(3)) as a function of at 25 degrees C. Plots of the pseudo-first-order rate constants (k(obs)) for methanolysis as a function of [La(OTf)(3)](total) were obtained under buffered conditions from 5.15 to 10.97, and the slopes of the linear parts of these were used to determine the second-order rate constants (k(2)(obs)) for the La(3+)-catalyzed methanolysis of 2. Detailed analysis of the potentiometric titration data of La(OTf)(3) in methanol through fits to a multicomponent equilibrium mixture of dimers of general stoichiometry La(3+)(2)((-)OCH3)n, where n assumes values of 1-5, gives the equilibrium distribution of each as a function of. These data, when fit to a second expression describing k(2)(obs) in terms of a linear combination of individual rate constants k(2)(2:1), k(2)(2:2).k(2)(2:)n for the dimers, allow one to describe the overall catalytic profile in terms of the individual contributions. The most catalytically important species are the three dimers La(3+)(2)((-)OCH3)1, La(3+)(2)((-)OCH3)2, and La(3+)(2)((-)OCH3)3. The catalysis of the methanolysis of 2 is spectacular: a 2 x 10(-3) M solution of [La(3+)](total), at neutral, affords a 10(9)-fold acceleration relative to the base reaction (t(1/2) approximately 20 s at 8.2) with excellent turnover. A mechanism of the catalyzed reaction involving the La(3+)(2)((-)OCH3)2 species is proposed.     

New SrAl2B2O7:Eu2+, Mn2+ phosphors for white light-emitting diodes

A series of Eu(2+) and Mn(2+) co-doped SrAl(2)B(2)O(7) phosphors were prepared by solid-state reaction method. X-ray powder diffraction (XRD) and photoluminescence excitation and emission were employed to characterize the phosphors. The results show that energy transfers between Eu(2+)and Mn(2+) ions. As the content of Ca(2+) ions in Ca(x)Sr(0.92-x)Al(2)B(2)O(7):Eu(2+)(0.06), Mn(2+)(0.02) phosphors increased, the CIE coordinates decreased and close to the white color standard mandated by the National Television Standard Committee (NTSC). Meanwhile, a white LED (light-emitting diode) was fabricated by combining the Ca(0.5)Sr(0.42)Al(2)B(2)O(7):Eu(2+)(0.06), Mn(2+)(0.02) phosphors with a 370 nm InGaN chip. The color coordinate of the fabricated white LED was also close to the white color standard, indicating that the Ca(0.5)Sr(0.42)Al(2)B(2)O(7):Eu(2+)(0.06), Mn(2+)(0.02) phosphor is a promising single-host phosphor that can be used in white LEDs.     

Tuning charge recombination rate constants through inner-sphere coordination in a copper(I) donor-acceptor compound

The coordination compounds [Cu(bpy-MV2+)(PPh3)2](PF6)3, where bpy-MV2+ is the 1-(4-(4'-methyl-2,2'-bipyridin-4-yl)butyl)-1'-methyl-4, 4'-bipyridinediium(2+) cation, and [Cu(dmb)(PPh3)2](PF6), where dmb is 4,4'-dimethyl-2,2'-bipyridine, have been prepared and characterized. Visible light (417 nm) excitation of [Cu(bpy-MV2+)(PPh3)2]3+ at room temperature leads to rapid intramolecular electron transfer, kcs > 1 x 10(8) s-1, to form a charge-separated state with an electron localized on the pendant viologen group and a copper(II) metal center, abbreviated [CuII-bpy-MV.+]. This state recombines to ground-state products with first-order rate constants that can be tuned with solvent over a approximately 10(7)-10(5) s-1 range. The activation parameters were determined from temperature-dependent electron-transfer data with Arrhenius analysis. A model is proposed wherein a solvent molecule is coordinated to Cu(II) in the charge-separated state, [(S)CuII-bpy-MV.+]. Visible light excitation of [Cu(dmb)(PPh3)2](PF6) in argon-saturated dichloromethane produces long-lived photoluminescent excited states, tau = 80 ns, that are dynamically quenched by the addition of Lewis basic solvents. The measured quenching constants each correlate well with the lifetime of the charge-separated state measured after excitation of [Cu(bpy-MV2+)(PPh3)2]3+ in the corresponding solvent.     

The use of outer-sphere complex formation reactions in ion-exchange chromatography Separation of oxalate and sulphate ions

It has been found that outer-sphere complex formation reactions can be used to increase the selectivity of ion-exchange separations. A method has been developed for the quantitative separation of sulphate and oxalate. The stability constants of the sulphate and oxalate complexes of tris(ethylenediamine) cobalt(III) and hexa-amminecobalt(III) have been determined at different ionic strengths from the elution volumes and the parameters of the ion-exchanger bed, and the values at I = 0 have been obtained by extrapolation. They are log K[Co(en)(+3)(3) + SO(2-)(4)] = 3.38; log K[Co(NH(3))(3+)(6) + SO(2-)(4) = 3.60; log K[Co(en)(3+)(3) + C(2)O(2-)(4) = 3.23.     

Structure of the Aqua Ions and Fluoride Complexes of Uranium(IV) and Thorium(IV) in Aqueous Solution an EXAFS Study

The structures of aqueous M(4+)(aq) and MF(3+)(aq), where M is uranium(IV) or thorium(IV), have been determined by L(III) edge EXAFS using data from solutions of 1.5 M HClO(4) in which the M(IV) concentrations ranged from 0.03 to 0.3 M. A least-squares refinement of the data for the aqua ions indicated 10.8 +/- 0.5 water molecules in the first hydration sphere of both ions and M-O bond distances for U(IV) and Th(IV) of 2.42 +/- 0.01 and 2.45 +/- 0.01 ?, respectively. By considering both previous structure information and the EXAFS data, we selected N = 10 +/- 1 as the most likely coordination number of both M(IV) aqua ions. EXAFS measurements from acidic aqueous uranium(IV) and thorium(IV) solutions containing fluoride show that large changes in the first coordination sphere occur. The experimental data indicates an asymmetrical distribution of the distances, probably as a result of differing M-F and M-O bond lengths. These can be described by a model that contains two different bond distances, one M-F distance at 2.10 ? and one M-O distance at 2.45 ? for U(IV); for Th(IV), the corresponding distances are 2.14 and 2.48 ?. The total coordination number in this model is unchanged from the aqua ions, i.e., 10 +/- 1.     

The use of outer-sphere complex formation reactions in ion-exchange chromatography Separation of maleate and fumarate ions

Outer-sphere complex formation reactions have been used to increase the selectivity of ion-exchange separation of maleate and fumarate ions. The stability constants of the maleate and fumarate complexes of tris(ethylenediamine)cobalt(III) and hexa-amminecobalt(III) have been determined at different ionic strengths from the elution volumes and the parameters of the ion-exchanger bed, and the values at I = 0 obtained by extrapolation. They are: log K [Co(en)(3+)(3) + Ma(2-)] = 3.33; log K [Co(NH(3))(3+)(6) + Ma(2-)] = 3.77; log K [Co(en)(3+)(3) + Fu(2-)] = 1.19; log K [Co(NH(3))(3+)(6) + Fu(2-)] = 1.99. The two anions can be separated quantitatively.