Solid phase extraction of heavy metal ions based on a novel functionalized magnetic multi-walled carbon nanotube composite with the aid of experimental design methodology

We report that magnetic multiwalled carbon nanotubes functionalized with 8-aminoquinoline can be applied to the preconcentration of Cd(II), Pb(II) and Ni(II) ions. The parameters affecting preconcentration were optimized by a Box-Behnken design through response surface methodology. Three variables (extraction time, magnetic sorbent amount, and pH value) were selected as the main factors affecting sorption, and four variables (type, volume and concentration of the eluent; elution time) were selected for optimizing elution. Following sorption and elution, the ions were quantified by FAAS. The LODs are 0.09, 0.72, and 1.0 ng mL^?1 for Cd(II), Ni(II), and Pb(II) ions, respectively. The relative standard deviations are <5.1 % for five separate batch determinations at 30 ng mL^?1 level of Cd(II), Ni(II), and Pb(II) ions. The sorption capacities (in mg g^?1) of this new sorbent are 201 for Cd(II), 150 for Pb(II), and 172 Ni(II). The composite was successfully applied to the rapid extraction of trace quantities of heavy metal ions in fish, sediment, soil, and water samples.

Synthesis,characterization, spectrophotometric and electrochemistry studies,and DNA cleavage of copper(II) complexes of a new azacrown bis-macrocycle and its mono-cyclic analogue

A new azacrown bis-macrocycle (5) and its mono–cyclic analogue (7) were synthesized and characterized by FT-IR, ¹H NMR, ¹³C NMR, DEPT ¹³C NMR, MS, and elemental analysis. The reaction with copper(II) nitrate yielded the corresponding complexes, formulated as Cu(5)(NO₃)₂·3H₂O (8), and Cu(7)(NO₃)₂·2.5H₂O (9). Also the stoichiometries of the complexes were determined in alcoholic solution and the results show that for both complexes the ratio of ligand to metal was 1:1 in methanol. The redox behavior of both complexes has been studied by cyclic voltammetry in DMF. Cyclic voltamogram of 8 shows quasi-reversible Cu^II/Cu^I redox couple whereas 9 shows a reversible Cu^II/Cu^I redox couple. Mono- and bis-macrocycle copper(II) complexes (8 and 9 respectively) cleaved plasmid pGS2 DNA by using an oxidative mechanism with 3- mercaptopropionic acid (MPA) as the reductant under aerobic conditions. The bis-macrocycle copper(II) complex 8 showed higher cleavage efficiency than their mono-macrocycle analogue 9 at the same Cu²⁺ concentration.     

Photocatalytic degradation of RhB,MG, MB,Roz.B, 3-BL and CI-50 by PW12-APTES@MCF as nanosized mesoporous photocatalyst

Surface of mesocellular silica foam (MCF) was modified by grafting 3-aminopropyltriethoxysilane (APTES) to have the positive charge, and thus, to provide sites for the immobilization of H₃PW₁₂O₄₀ (PW₁₂). This modified-nanosized mesoporous silica (PW₁₂-APTES@MCF) was characterized by FTIR, XRD, BET and TEM. The photoefficiency of this nanosized mesoporous toward photodegradation of six dye solutions [rhodamine B, malachite green, methylene blue, rose bengal, solophenyl red (3-BL), yellow direct 50 (CI-50)] was investigated in a photocatalytic reactor using UV lamp as a light source. The effect of various experimental parameters on the degradation performance of the process was evaluated by examining catalyst dosage, initial dye concentration and pH of the dye solution in the presence of PW₁₂-APTES@MCF. The photocatalytic behaviors of the PW₁₂-APTES@MCF were also compared with two mesoporous silica-supported PW₁₂-APTES@SBA-15 and PW₁₂-APTES@KIT-6. It indicated that the PW₁₂-APTES@MCF had the highest photocatalytic efficiency among three mesoporous silica-supported PW₁₂-APTES. These photocatalysts can be reused several times although they get less active.     

DFT Calculations and NBO Analysis of 2-Chloroethylethyldichlorosilane Unimolecular Elimination Kinetics in the Gas Phase

Ab initio molecular orbital calculations have been used to investigate the thermal decomposition kinetics of 2-chloroethylethyldichlorosilane at the B3LYP/6-311+G**,B3PW91/6-311+G**,and MPW1PW91/6-311+G** levels of theory.Among these methods,the results(activation parameters) obtained using the B3LYP/6-311+G** level are in good agreement with the available experimental data.The calculated data imply that in the unimolecular β-elimination reactions of the studied compound in the gas phase,the polarization of C(1)-Cl(3) and C(1)-H(4) bonds in the sense of C(1)δ+-Cl(3)δ-and C(1)δ+-H(4)δ-,respectively,is a determining factor in the gas phase elimination reactions 1,2 and 3.Analysis of bond order,natural bond orbital charges,bond indexes,synchro-nicity parameters,and IRC calculations suggest the elimination of 2-chloroethylethyldichlorosilane via reactions 1～3 can be described as concerted and slightly asynchronous.The transition state structures of these reactions are a four-membered cyclic structure.     

Volumetric and Viscometric Studies of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-Bis(salicylaldehyde)-1,3-diaminopropane Schiff Base (Salpr) in Ionic Liquid + DMF solutions

The apparent molar volumes and viscosities of N,N′-bis(salicylaldehyde)-1,3-diaminopropane Schiff base (Salpr) have been determined in ionic liquid {1-pentyl-3-methylimidazolium bromide ([PnMIm]Br)} + N,N-dimethylformamide (DMF) solutions at 298.15 K from density and viscosity measurements using a vibrating tube densimeter and übbelohde type viscometer, respectively. These data have been used to calculate standard partial molar volumes, V_f ⁰V_{\phi} ^{0}, transfer partial molar volumes, Δ_tr V ⁰, and viscosity B-coefficients of the solutions. The transfer partial molar volumes are negative, and decrease with increasing the concentration of ionic liquid for all of the investigated solutions. It found that this ionic liquid interacts strongly with the Schiff base (Salpr) and has desolvation effect on the Schiff base molecules.     

Synthesis of new unsymmetrical 4,5-dihydroxy-2-imidazolidinones. Dynamic NMR spectroscopic study of the prototropic tautomerism in 1-(2-benzimidazolyl)-3-phenyl-4,5-dihydroxy-2-imidazolidinone

The acid-catalyzed cyclocondensation in refluxing acetonitrile of aqueous glyoxal with N-heteroaryl-N'-phenylureas 4a-f (heteroaryl = 2-thiazolyl, 2-pyrimidinyl,2-pyrazinyl, 2-pyridinyl, 3-pyridinyl and 2-benzimidazolyl) led to the formation of the corresponding 1-heteroaryl-3-phenyl-4,5-dihydroxy-2-imidazolidinones 5a-f. All the products were characterized by elemental and spectroscopic analyses. The free-energy barrier (Delta G not equal) for prototropic tautomerism in 1-(2-benzimidazolyl)-3-phenyl-4,5-dihydroxy-2-imidazolidinone (5f) was determined by dynamic NMR studies to be 81 +/- 2 KJ mol(-1).     

A simple, solvent and catalyst-free green synthesis of novel N-[(1H-indol-3-yl)arylmethyl]heteroarylamines

One-pot, three-component coupling reactions of indole, aromatic aldehydes, and heteroaryl amines under solvent-free conditions lead to the formation of the corresponding novel 3-[(N-heteroaryl)(aryl)methyl]indoles in moderate to high yields. The key features of this multi-component reaction are the simple reaction procedure, no organic solvent or acid catalyst, and easy product separation without further purification.     

Synthesis,characterization and crystal structures of dinuclear macrocyclic Schiff base copper(I) complexes bearing different bridges

Utilizing a new 20-membered macrocyclic Schiff base ligand with two coordination sites formed from the [2+2] condensation of 1,3-diaminopropane and benzene-1,3-dicarboxaldehyde in the presence of CuX (X = Cl⁻, Br⁻, I⁻) salts, air-stable dicopper(I) complexes were synthesized in acetonitrile, intramolecularly linked via two halide groups, and characterized by different physico-chemical techniques. The single crystal X-ray diffraction technique indicates these complexes consist of two N₂X₂ donor sets that have distorted tetrahedral coordination environments around the copper(I) ions. In these halogen-bridged binuclear Cu₂LX₂ systems the Cu?Cu separation can be controlled, as this distance is reduced on increasing the halide size and hence the X?X repulsion, with the rigidity of the macrocycle playing a significant role.     

Higher dimensional Shimura varieties in the Prym loci of ramified double covers

In this paper, we construct Shimura subvarieties of dimension bigger than one of the moduli space ${\mathsf{A}}_p^{\delta }$ of δ-polarized abelian varieties of dimension p, which are generically contained in the Prym loci of (ramified) double covers. The idea is to adapt the techniques already used to construct Shimura curves in the Prym loci to the higher dimensional case, namely, to use families of Galois covers of ${\mathbb{P}}^1$. The case of abelian covers is treated in detail, since in this case, it is possible to make explicit computations that allow to verify a sufficient condition for such a family to yield a Shimura subvariety of ${\mathsf{A}}_p^{\delta }$.