ClO<Subscript>4</Subscript><Superscript>−</Superscript>/Zr-MCM-41 nanoparticles prepared at mild conditions: a novel solid acid catalyst for the synthesis of polyhydroquinolines

One-pot four-component reaction of aldehydes, dimedone, ethyl cyanoacetate or ethyl acetoacetate and ammonium acetate was studied in the presence of perchlorated Zr-MCM-41 (ClO₄ ^?/Zr-MCM-41) nanoparticles for the synthesis of dihydropyridines. Zr-MCM-41 nanoparticles with various molar ratios of Si/Zr were synthesized by sol–gel method under mild conditions, and then ClO₄ ^?/Zr-MCM-41 samples with different calcination temperatures were prepared and characterized by XRD, FT-IR and SEM techniques. The characterization results show the presence of perchlorate in the mesostructure of Zr-MCM-41 and the catalytic performance experiments show that ClO₄ ^?/Zr-MCM-41 with Si/Zr molar ratio of 25 and calcinations temperature of 300 °C has the best catalytic activity. The catalyst can be recovered easily and reused many times with moderate decrease in activity.     

A new method of synthesis of the B<Subscript>3</Subscript>H<Stack><Subscript>8</Subscript><Superscript>−</Superscript></Stack> anion

A new method of synthesis of the B₃H₈⁻ anion has been suggested. The method uses the reaction of some metal halides (CuCl, SnCl₂, CrCl₃, PbF₂, PbCl₂, PbBr₂, and BiCl₃) with sodium tetrahydroborate. It is characterized by high (up to quantitative) yields and simplicity of isolation of the target products ((n-C₄H₉)₄N)[B₃H₈] and Cs[B₃H₈].     

Influence of ion size on the stability of chloroplumbates containing PbCl<Stack><Subscript>5</Subscript><Superscript>−</Superscript></Stack> or PbCl<Stack><Subscript>6</Subscript><Superscript>2−</Superscript></Stack>

The enthalpies of formation of PbCl₄, PbCl₅⁻ and PbCl₆²⁻, originating from quantum mechanics, have enabled the thermodynamic behaviour of these ions with respect to Cl-detachment to be assessed. The stability of salts containing PbCl₅⁻ and PbCl₆²⁻ as a function of the dimensions of these anions and complementary cations was studied using an approach combining the Kapustinskii-Yatsimirskii equation with basic thermochemical relationships. It was found that hexachloroplumbates of monovalent metal cations will not dissociate into metal chlorides and PbCl₄, provided the complementary cations are suitably large in size. Hexachloroplumbates of divalent metal cations have not yet been synthesised since no known metal cations attain the requisite large size. Such salts will not dissociate if the divalent metal cations are able to complex suitably large electron-donating ligands. The pentachloroplumbates of both monovalent and divalent metal cations are unstable, since no known metal cations have appropriately large ionic radii. The approach adopted appears to be useful for the examination of the thermal behaviour, stability and reactivity of chloroplumbates.     

Identification of Anionic Supramolecular Complexes of Sulfonamide Receptors with Cl<Superscript>−</Superscript>, NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> by APCI-MS

As part of a mass spectrometric investigation of the binding properties of sulfonamide anion receptors, an atmospheric pressure chemical ionization mass spectrometric (APCI-MS) method involving direct infusion followed by thermal desorption was employed for identification of anionic supramolecular complexes in dichloromethane (CH₂Cl₂). Specifically, the dansylamide derivative of tris(2-aminoethyl)amine (tren) (1), the chiral 1,3-benzenesulfonamide derivatives of (1R,2S)-(+)-cis-1-amino-2-indanol (2), and (R)-(+)-bornylamine, (3), were shown to bind halide and nitrate ions in the presence of (n−Bu)₄N⁺X⁻ (X⁻ = Cl⁻, NO₃⁻, Br⁻, I⁻). Solutions of receptors and anions in CH₂Cl₂ were combined to form the anionic supramolecular complexes, which were subsequently introduced into the mass spectrometer via direct infusion followed by thermal desorption. The anionic supramolecular complexes [M+X]⁻, (M=1–3, X⁻=Cl⁻, NO₃⁻, Br⁻, I⁻) were observed in negative mode APCI-MS along with the deprotonated receptors [M−H]⁻. Full ionization energy of the APCI corona pin (4.5 kV) was necessary for obtaining mass spectra with the best signal-to-noise ratios.     

The ESCA analysis of the B<Subscript>3</Subscript>H<Stack><Subscript>8</Subscript><Superscript>−</Superscript></Stack> anion

Compounds [Et₄N]₂B₃H₈ and CsB₃H₈ are studied using the ESCA method. The results of analysis of the B1s electron spectra and estimation of the effective charge differences in [Et₄N]₂B₃H₈ are compared to the data of theoretical calculations of the B₃H₈⁻ anion.     

Isothermal solubility diagram of the 2Na<Superscript>+</Superscript>,Mg<Superscript>2+</Superscript>‖2Cl<Superscript>−</Superscript>, 2ClO<Stack><Subscript>3</Subscript><Superscript>‒</Superscript></Stack>-H<Subscript>2</Subscript>O quaternary system at 20 and 100°C

The solubility in the 2Na⁺,Mg²⁺‖2Cl⁻, 2ClO₃⁻-H₂O system was studied at 20 and 100°C and the solubility diagrams were plotted. New compounds were not found to form in the title quaternary reciprocal system. The sodium chloride field was observed to expand with rising temperature.     

Hydroisomerization of benzene-containing gasoline fractions on a Pt/SO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack>-ZrO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst: III. The hydrogenating properties of the catalyst

The properties and state of platinum in Pt/SO₄²⁻-ZrO₂-Al₂O₃ catalysts with various alumina contents have been investigated in benzene hydrogenation as a model reaction using IR spectroscopy, temperature-programmed reduction, and H₂ chemisorption. As the Al₂O₃ content is raised, the hydrogenating activity of the catalyst increases, which is due to the increasing proportion of metallic platinum on the surface.     

Study on nonlinear kinetic and thermodynamics of oscillating reaction of amino Acid-BrO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack>-Mn<Superscript>2+</Superscript>-H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-acetone system

With the help of the kinetic parameters (the rate constant (k _in k _p) and the apparent activation energy (E _in E _p) of the oscillatory induction period and oscillation period) of the oscillating reaction using thirteen amino acids, leucine (Leu), threonine (Thr), arginine (Arg), lysine (Lys), histidine (His), alanine (Ala), glutamine (Glu), glycine (Gly), methionine (Met), cystine (Cys), tryptophan (Trp), serine (Ser) and tyrosine (Tyr), as organic substrates in amino acid-BrO₃⁻-Mn²⁺-H₂SO₄-acetone system, then based on the Oregonator model and the thermodynamics theory on irreversible process, the thermodynamic function (ΔH _in, ΔG _in, ΔS _in and ΔH _p, ΔG _p, ΔS _p) of these oscillating system are studied. The results indicate the entropy ΔS of these oscillating reaction are negative, thereby it is proved that the oscillating reaction is a noequilibrium system with dissipation structure in agreement with the character of the oscillating reaction from disorder to order in irreversible thermodynamics. These are satisfactorily to explain the experimental phenomena.     

The effect of NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack> and OH<Superscript>−</Superscript> ions on the laser ablation of Cs<Superscript>+</Superscript> ion on Type 304 stainless steel

Type 304 stainless steel specimens artificially contaminated with CsCl solution were treated with KOH solution and KNO₃ solution, respectively. Cs⁺ ion removal tests by a Q-switched Nd:YAG laser at 1064 nm at a given fluence of 57.3 J/cm² were performed. The surface morphology and the relative atomic mole ratio of the specimen surface were investigated by SEM and EPMA. The order of Cs⁺ ion removal efficiency of laser was no-treatment < KOH < KNO₃ during the 42 shots. From the investigation of XPS peaks around 532.7 and 292.9 eV, KNO₃ on a surface of specimen was found to be fully decomposed during the laser irradiation. It was suggested that Cs₂O particulates formed by the reaction between the reactive oxygen generated from the nitrate ion and Cs⁺ ion on the metal surface could be easily suspended. For the KOH system, FeOOH was formed during the laser irradiation and it changed into Fe₂O₃. It was also suggested that Cs₂O particulates were formed by the reaction between the reactive oxygen generated from the decomposition of K₂O and Cs⁺ ion on the metal surface..     

Comparison of Magnetic Properties between Spin Singlet and Triplet Li<Subscript>3</Subscript>Al<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> Clusters

With a second-order Møller–Plesset perturbation theory and Hartree–Fock nuclear magnetic resonance calculations, we investigated the magnetic properties of spin singlet and triplet Li₃Al ₄ ^? clusters. The obtained gauge-independent atomic orbital magnetic shielding tensors confirm the paramagnetism of singlet Li₃Al ₄ ^? and diamagnetism of the triplet. The planar rings composed of four aluminum atoms make the magnetic properties of Li₃Al ₄ ^? clusters versatile. The localized molecular orbital, low symmetry of geometric conformation and narrow gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital are found to correlate with the paramagnetism of singlet Li₃Al ₄ ^? . The origin of the paramagnetism is explained. In triplet Li₃Al ₄ ^? , the two outmost orbitals are degenerate, causing a conversion from the paramagnetism to diamagnetism.     

Computational studies of the interactions of I<Superscript>−</Superscript> and I<Subscript>3</Subscript><Superscript>−</Superscript> with TiO<Subscript>2</Subscript> clusters: implications for dye-sensitized solar cells

Abstract  

First principle density-functional theory calculations have been carried out on the interaction of I⁻ and I₃ ⁻ with TiO₂ anatase surfaces, modeled by finite clusters that range in size from 48 to 180 atoms. The total energy per TiO₂ unit and the HOMO-LUMO gaps decrease with increasing the size of the clusters. Both redox species (I⁻ and I₃ ⁻) are strongly adsorbed on the TiO₂ surface with the adsorbtion of I⁻ being stronger. Adsorption of triiodide leads to its dissociation. The positions of the HOMO and LUMO of the adsorbed systems shift negatively from their respective cluster values. Solvation effects have been modeled using the CPCM model. Introducing solvent reduces the shifting of HOMO and LUMO. Implications for dye-sensitized solar cells (DSSC) are discussed. Both the HOMO-LUMO shifting and the strong adsorption might affect the performance of the cell.     

Preparation of nano-SO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack>/TiO<Subscript>2</Subscript> catalyst and its application in esterification of sebacic acid with 2-ethyl hexanol

A pure anatase phase nano-SO₄²⁻ /TiO₂ catalysts were synthesized and their catalytic activities were tested. Nano-SO₄²⁻/TiO₂ shows high activity and effective re-usable when used as basic catalysts for the synthesis of dioctyl sebacate.     

A molecular dynamics simulation of H<Subscript>3</Subscript>PO<Subscript>4</Subscript>, H<Subscript>2</Subscript>PO<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack>, and the protonated form of N,N-dimethylformamide in liquid N,N-dimethylformamide

The molecular dynamics simulation method was for the first time used to study the structural and energy parameters of H₃PO₄, H₂PO₄⁻, and (DMFA)H⁺ (protonated dimethylformamide) in liquid N,N-dimethylformamide. The predominant orientation of the nearest neighbors of H₃PO₄, H₂PO₄⁻, DMFA, and (DMFA)H⁺ was determined from ranked distribution functions. The most probable structure of H-bonded complexes was obtained. It was shown that H₃PO₄ formed H-bonds with two DMFA molecules, and and (DMFA)H⁺ formed H-bonds with one molecule. The dependence of Coulomb interaction energies on the distance between H₃PO₄, H₂PO₄⁻, (DMFA)H⁺, and DMFA had the form of damped oscillations, as is characteristic of intermolecular interactions in pure DMFA. The molecular dynamics simulation of the H₂PO₄⁻-(DMFA)H⁺-DMFA ternary system showed a high probability of the formation of contact ion pairs.     

Experimental Determination of the Isotherm at 15°C of the System Mg<Superscript>2+</Superscript>/Cl<Superscript>−</Superscript>, SO<Subscript>4</Subscript><Superscript>2</Superscript>–H<Subscript>2</Subscript>O

Summary.  The diagram of the ternary system Mg²⁺/Cl⁻, SO₄ ²⁻–H₂O was established at 15°C by means of analytical and conductimetric measurements. Three compounds were found in this diagram, which are MgSO₄·6H₂O, MgSO₄·7H₂O, and MgCl₂·6H₂O. The solubility field of MgSO₄·7H₂O is important whereas those of MgSO₄·6H₂O and MgCl₂·6H₂O are small. The compositions (mass-%) of the two invariant points determined by the two methods are: MgSO₄:MgCl₂=2.73:33.80 and MgSO₄: MgCl₂=3.38:28.91. Both the measured and the calculated isotherm at 15°C have been used for modelling of the diagram Mg²⁺/Cl⁻, SO₄ ²⁻–H₂O between 0 and 35°C. The polythermal invariant point was approximately located between 15 and 10°C.  Corresponding author. E-mail: ariguib@planet.tn Received October 16, 2002; accepted (revised) December 3, 2002 Published online April 24, 2003 RID="a" ID="a" Dedicated to Prof. Dr. Heinz Gamsj?ger on the occasion of his 70^th birthday     

Synthesis and Structure of the bismuth complex [Ph<Subscript>3</Subscript>PrP]<Stack><Subscript>4</Subscript><Superscript>+</Superscript></Stack>[Bi<Subscript>4</Subscript>I<Subscript>16</Subscript>]<Superscript>4−</Superscript>

The complex [Ph₃P] ₄ ⁺ [Bi₄I₁₆]^4? · 2 Me₂C=O (I) was synthesized by the reaction of triphenyl(propyl)phosphonium iodide with bismuth iodide in acetone. The crystal structure of complex I was determined by X-ray crystallography. It contains, in addition to solvent molecules, two types of crystallographically independent tetrahedral tetraphenyl(propyl)phosphonium cations and tetranuclear anions [Bi₄I₁₆]^4? in a chair conformation with the bismuth atoms being in an octahedral coordination. The Bi-I distances in the anion vary within 2.8768(4)–3.2524(4) Å.     

Chemical Bonding in the Complexes XeF<Stack><Subscript>5</Subscript><Superscript>+</Superscript></Stack>XF<Stack><Subscript>6</Subscript><Superscript>−</Superscript></Stack> (X = P,As, Sb,and Bi)

Ab initio quantum-chemical calculations of the complexes XeF ₅ ⁺ XF ₆ ^? (X = P, As, Sb, and Bi) were performed with the use of relativistic pseudopotentials for heavy atoms and full-electron basis sets. The chemical bonds were characterized by the parameters of critical points (electron density, its Laplacian, total electron energy, and its kinetic and potential components). It was demonstrated that the interaction between the XeF ₅ ⁺ cation and the XF ₆ ^? anion in XeF ₅ ⁺ XF ₆ ^? follows a key-lock scheme involving directed interactions of bridging fluorine atoms F_b → Xe and that the structuring function of the lone electron pair of the Xe atom is to compensate the destabilizing electrostatic interaction between the Xe and X atoms bearing excess positive charges.     

Study on the thermal behavior of the complexes of the type [PdX<Subscript>2</Subscript>(tdmPz)] (X = Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>, I<Superscript>−</Superscript>, SCN<Superscript>−</Superscript>)

Four new mononuclear Pd(II) complexes of the type [PdX₂(tdmPz)] {X = Cl⁻ (1); Br⁻ (2); I⁻ (3); SCN⁻ (4); tdmPz = 1-thiocarbamoyl-3,5-dimethylpyrazole} have been synthesized and characterized by elemental analysis, IR spectroscopy, ¹H and ¹³C{¹H}-NMR experiments. The thermal behavior of the complexes 1–4 has been investigated by means of thermogravimetry (TG) and differential thermal analysis (DTA). From the initial decomposition temperatures, the thermal stability of the complexes can be ordered in the sequence: 3 < 4 ≡ 2 < 1. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

SO<Stack><Subscript>2</Subscript><Superscript>−·</Superscript></Stack> electron transfer ion/ion reactions with disulfide linked polypeptide ions

Multiply-charged peptide cations comprised of two polypeptide chains (designated A and B) bound via a disulfide linkage have been reacted with SO2-* in an electrodynamic ion trap mass spectrometer. These reactions proceed through both proton transfer (without dissociation) and electron transfer (with and without dissociation). Electron transfer reactions are shown to give rise to cleavage along the peptide backbone, loss of neutral molecules, and cleavage of the cystine bond. Disulfide bond cleavage is the preferred dissociation channel and both Chain A (or B)-S* and Chain A (or B)-SH fragment ions are observed, similar to those observed with electron capture dissociation (ECD) of disulfide-bound peptides. Electron transfer without dissociation produces [M + 2H]+* ions, which appear to be less kinetically stable than the proton transfer [M + H]+ product. When subjected to collision-induced dissociation (CID), the [M + 2H]+* ions fragment to give products that were also observed as dissociation products during the electron transfer reaction. However, not all dissociation channels noted in the electron transfer reaction were observed in the CID of the [M + 2H]+* ions. The charge state of the peptide has a significant effect on both the extent of electron transfer dissociation observed and the variety of dissociation products, with higher charge states giving more of each.     

Enthalpy of solution of VOCl<Subscript>3</Subscript> in dilute sodium hydroxide solutions and the standard enthalpy of formation of the HVO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack> ion

The calorimetric enthalpies of solution of liquid vanadium oxytrichloride in dilute sodium hydroxide solutions were measured at 298.15 K and ionic strengths I = 0.5, 1.0, or 1.5 (NaClO₄). The standard enthalpy of formation of the HVO ₄ ^2? ion was calculated from the measured data.