The use of ultrasonic treatment for improvement of metrological performance of sorption atomic absorption determination of lead(II) and cadmium(II) traces

The optimal parameters for ultrasonic treatment (frequency 200–300 kHz, intensity 2–4 W cm^?2) were obtained to intensify Pb(II) and Cd(II) sorption concentration by carbon sorbent from apricot pit. The combined action of ultrasonic frequency of 18 kHz and 1 MHz on concentrate slurry increases its sedimentation stability from 3 to 180 minutes and decreases S_r value up to 7% at Pb(II), Cd(II) hybrid sorption atomic absorption determination in natural waters, brines, common salt.      

Stereoselective preparation of mono- and bis-derivatives of pentacyclo[6.3.0.02,6.03,10.05,9] undecane (D 3-trishomocubane)

The rearrangement of easily accessible Cookson’s diketone with chlorosulfonic acid in chloroform followed by the acidic hydrolysis gave 6-chloro-7-hydroxy-dichloropentacyclo[6.3.0.0^2,6.0^3,10.0^5,9]undecane-4-one, whose syn-stereochemistry was assigned through the X-ray crystal structure analysis. This key structure was used for the stereoselective synthesis of the D ₃-trishomocubane derivatives as well as for the preparation of potential drugs bearing hydroxy- and amino-functional groups. A new multigram preparative synthesis of D ₃-trishomocubane was developed.      

Polymer conjugates with potential biological activity based on new derivatives of 2-mercaptobenzoxazole-synthesis and characterization

New potentially biologically active compounds derived from 2-mercapto-benzoxazole were synthesized and coupled on polymeric support of poly (maleic anhydride-alt-vinyl acetate) for the preparation of polymer-drug conjugates with controlled drug release. All compounds were characterized by elemental and spectroscopy (FT-IR, ¹H-NMR) analysis. The toxicological tests recommend the products for further laboratory screening.      

Copper-cobalt ferrites as catalysts for methanol decomposition

Copper-cobalt ferrites with composition Cu_1?xCo_xFe₂O₄, where x= 0.2 and 0.8 were prepared by thermal treatment of co-precipitated precursor. The obtained materials were characterized by TG-DSC, XRD, Transmission and Conversion Electron Mössbauer spectroscopy and temperature programmed reduction with hydrogen. The catalytic properties of ferrites were tested in methanol decomposition to CO and hydrogen.      

The synthesis, structure and physical properties of lanthanide(III) complexes with nicotinic acid

This article reports the synthesis of novel, rare-earth coordination complexes with nicotinic acid. Three compounds with the general formula Ln₂[(C₅H₄NCOO)₆(H₂O)₄] (Ln = Yb, 1; Ln = Gd, 2; Ln = Nd, 3) were prepared from relatively cheap and readily available reactants. Their compositions and structure were characterized by IR spectroscopy and single-crystal X-ray diffraction. The magnetic and thermogravimetric properties were also studied. The complexes consist of centrosymetric, dimeric molecules having all six nicotinato ligands coordinated with the central atom in the bidentate mode. The coordination environment of the Ln³⁺ for all three compounds is 8. Here we describe the crystal structure of Yb and Gd complexes with nicotinic acid.      

Investigation of electrical properties of PANI/chalcogenide junctions

Pure Polyaniline (EB) and Polyaniline doped with different protonic acids (ESs) were chemically synthesized using ammonium peroxydisulphate (APS) as an oxidant. Junctions have been prepared by evaporating chalcogenide materials (ZnSe, CdSe) on conducting polyaniline (EB & ESs) pellets using a vacuum evaporation technique. I–V characteristics of junctions have been studied at room temperature using the Keithley electrometer 6517A. I–V measurements show the rectification effect. A junction of ES[PO₄ ^3?] may be preferred over the other junctions due to its low ideality factor and maximum rectification ratio.      

Characterization of the passive films on electrodeposited Fe-Ni-Cr alloys in borate solution at pH 8.4

The corrosion properties of the passive layers formed on iron-nickel-chromium electrodeposits of Fe₂₉Ni₅₁Cr₂₀ were investigated in 0.3 M borate solution at a‘ pH of 8.4. On the basis of measurements by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy, a low passive dissolution/corrosion rate was identified for the electrodeposited Fe-Ni-Cr alloys due to the nature of the established corrosion layer. The stability of this passive layer was further enhanced after corrosion under oxidizing conditions. Mössbauer spectroscopic measurements confirmed the existence of a thin passive layer on the amorphous electrodeposits.      

Complexes of platinum and palladium with 4-nitrobenzoic hydrazide: synthesis and cytotoxic activity

New complexes of platinum and palladium were isolated with 4-nitrobenzoic hydrazide (4-NH) and characterized by spectroscopic techniques. Results show that the ligand is coordinated to metallic ions by the basic nitrogen of NH₂ group and have the general structure cis-[M(4-NH)₂X₂] where M= Pt or Pd and x = Cl or I. The compound III, [Pt(4-NH)₂I₂], was found to display cytotoxicity (IC₅₀ = 0.96 μmol L^?1) against the K562 tumoral cell line. This complex is significantly more cytotoxic than cisplatin.      

Novel ion-binding C3 symmetric tripodal triazoles: synthesis and characterization

Novel C₃ symmetric tripodal molecules were synthesized from cyclohexane 1,3,5-tricarboxylic acid. Utilizing click and Sonogashira reactions, ion-binding triazole and pyridazin-3(2H)-one units were incorporated to form polydentate ligands for ion complexation. The structures of the novel C₃ symmetric derivatives were extensively characterized by ¹H, ¹³C and 2D NMR techniques along with HRMS and IR. The copper(I)-binding potentials of these ligands were investigated by using them as additives in model copper(I)-catalysed azide-alkyne cycloaddition (CuAAC) reactions. The copper(I) complexation ability of our compound was also proved by different spectroscopic methods, such as mass spectrometry, UV and NMR spectroscopy. Based on the mass spectrometric data all of the C₃ symmetric ligands formed 1:1 complex with copper(I) ion. The specific role of C₃ symmetric polydentate form in the complexation process was also discussed      

Supramolecular complexes of podand ligands with xenon

Formation of stable complexes between xenon and podand polyoxyethylene ligands was ascertained. The complexation process was studied by ¹²⁹Xe NMR titration, NMR diffusiometry and heteronuclear NOE measurements. The ligands studied form a 1:1 complexes with Xe(0). Their stability constants depend on the ligand structure, i.e., polyoxyethylene chain length, number of complexating polyether units and the topology of the anchoring centre.      

Preparation of selectively protected protoescigenin derivatives for synthesis of escin analogs and neoglycoconjugates

Protoescigenin, the main aglycone of horse chestnut saponin mixture known as escin, was selected as substrate for exploratory chemistry towards selective protection, followed by propargyl ether formation and subsequent condensation with azido-monosaccharides, to obtain novel triazole linked conjugates of the triterpene.      

Reaction of barbituric acid with organic azides and phosphonium ylides

Amination by organic azides has been carried out to provide aminobarbiturates by fusion of a triazole ring to the 5,6-positions of barbituric acid followed by cleavage and thermal elimination of nitrogen, whereas aza-Wittig reaction gave phosphoranylidene barbituric acid salts.      

The first synthesis of 3-deoxyoripavine and its utilization in the preparation of 10-deoxyaporphines and cyprodime

The synthesis of 3-deoxyoripavine (7) was realized as a novel and promising intermediate towards the synthesis of the important class of dopaminergic and/or serotonergic 10-deoxyaporphines and the special pharmacological tool µ opioid antagonist cyprodime. Generally, the preparation of these valuable biologically active compounds was achieved in remarkable yields.      

Organoruthenium(II) thiosemicarbazone complexes: synthesis, spectral characterization, DNA binding and DNA cleavage studies

A series of new ruthenium(II) complexes were synthesized with Schiff bases derived from salicylaldehyde / o-hydroxyacetophenone/ o-vanillin / 2-hydroxy-1-naphthaldehyde with thiosemicarbazide and acetyl furan. They are characterized by elemental analysis, IR, electronic, ¹H NMR, ¹³C NMR and mass spectral studies. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). Four of these complexes were tested for its binding with CT-DNA using absorption spectroscopic studies and two of these complexes exhibit efficient DNA cleavage activity.      

Electrode processes of selected redox active substances on poly(o-aminophenol) film electrode

Using the method of cyclic voltammetry, the electrode process of Ni²⁺, Pb²⁺, Cu²⁺ and pyrocatechin on a poly(o-aminophenol) (PoAP) modified glassy carbon electrode (GCE) was investigated. The PoAP polymer was found to affect the redox process of copper and pyrocatechin. The use of polymer of different thicknesses showed that the obtained film has a dense, nonporous structure. The redox process of the examined substances may be considered as proceeding on the polymer surface. The PoAP polymer obtained in the described conditions takes part in charge transfer.      

Cobalt electrodeposition onto polycrystalline gold from ammoniacal solutions

In the present work, the cobalt electrodeposition onto polycrystalline gold electrodes from aqueous solutions containing 0.01M CoSO₄ + 1 M (NH₄)₂SO₄ at pH=7 was analyzed. Linear voltammetry results suggested a change in the kinetic of the cobalt electrodeposition. In all cases, the nucleation rate (A), the number of active nucleation sites (N ₀) and the saturation number of nuclei (N _s ) values were potential dependent. The calculated Gibbs free energy (ΔG) for this system was 1.88×10^?20 J nuclei^?1 and the transfer coefficient for the Hydrogen Electroreduction Reaction (HER) was 0.47.      

Extraction properties of β-aminophosphine oxides towards lanthanides and alkaline earth metals

The investigation of the extraction properties of a series of polyoligodentate β-aminophosphine oxides 1–8 bearing from one to six phosphine oxide groups in a molecule towards Ln(III) and alkaline earth metals ions from neutral media has revealed that, using common diluents, the extraction efficiency increases with an increase of a number of P=O functions in a ligand. The addition of ionic liquid, namely 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([bmim][NTf₂]), significantly increasing the extraction efficiency and application of IL concentration of 0.05 M (in 1,2-dichloroethane) providing the maximum recovery of metal ions with Lu/La separation factor reaching up to 91. Hexapodal tris[bis(2-diphenylphosphorylethyl)aminoethyl]amine 8 demonstrates the highest extraction under all conditions applied and the separation factor for U and Eu of this compound exceeded 10³.      

Comparative studies of Pd, Ru, Ni, Cu/ZnAl2O4 catalysts for the water gas shift reaction

The activity of monometallic Pd, Ru, Ni and Cu catalysts supported on spinel ZnAl₂O₄ for water gas shift reaction (WGS) was investigated. The physicochemical properties of each catalyst was studied by XRD, TPR, BET and chemisorption methods. The highest activity was obtained for Cu/ZnAl₂O₄ among the catalysts tested. The activation process carried out in a reducing atmosphere 5%H₂-95%Ar in the case of Cu/ZnAl₂O₄ system lead to the catalytic activity improvement. In the case of copper catalysts, the water gas shift reaction proceeded by the redox surface mechanism between Cu⁰/Cu⁺. The PdZn alloy formation after reduction at 350°C was shown.