Synthesis, characterization and electro-spectroelectrochemical studies of four macrocyclic Schiff-base Co(II) complexes having N2O2 set of donor atoms

Four macrocyclic Schiff-base cobalt complexes, [CoL¹][NO₃]₂ · 3H₂O, [CoL²][NO₃]₂ · 4H₂O, [CoL³][NO₃]₂ · 4H₂O and [CoL⁴][NO₃]₂ · 2H₂O, were synthesized by reaction of salicylaldehyde derivatives with 1,4-bis(3-aminopropoxy)butane or (±)-trans-1,2-diaminocyclohexane and Co(NO₃)₂ · 6H₂O by template effect in methanol. The metals to ligand ratio of the complexes were found to be 1:1. The Co(II) complexes are proposed to be tetrahedral geometry. The macrocyclic Co(II) complexes are 1:2 electrolytes as shown by their molar conductivities (Λ_M) in DMF (dimethyl formamide) at 10^?3 M. The structure of Co(II) complexes is proposed from elemental analysis, Ft-IR, UV–visible spectra, magnetic susceptibility, molar conductivity measurements and mass spectra. Electrochemical and thin-layer spectroelectrochemical studies of the complexes were comparatively studied in the same experimental conditions. The electrochemical results revealed that all complexes displayed irreversible one reduction processes and their cathodic peak potential values (E _pc) were observed in around of ?1.14 to 0.95 V. It was also seen that [CoL¹][NO₃]₂ · 3H₂O and [CoL²][NO₃]₂ · 4H₂O exhibited one cathodic wave without corresponding anodic wave but, [CoL³][NO₃]₂ · 4H₂O and [CoL⁴][NO₃]₂ · 2H₂O showed one cathodic wave with corresponding anodic wave, probably due to the presence of different ligand nature even if the complexes have the same N₂O₂ donor set. In view of spectroelectrochemical studies [CoL³][NO₃]₂ · 4H₂O showed distinctive spectral changes in which the intensity of the band (λ = at 316 nm, assigned to n → π* transitions) decreased and a new broad band in a low intensity about 391 nm appeared as a result of the reduction process based on the cobalt center in the complex.     

Synthesis,characterisation and dosimetric evaluation of MgB4O7 glass as thermoluminescent dosimeter

This study presumably reports the dosimetric properties of MgB₄O₇ glass system. A series of MgB₄O₇ glass samples with nominal compositions XMgO-(100-X) B₂O₃, with X?=?35, 40 and 45?mol% was successfully synthesied using conventional melt quenching method. The presence of broad humps and absence of any sharp peak in typical X-ray diffraction patterns confirm the amorphous nature of the synthesised glass samples. Good glass forming ability, 0.55, of the mixture resulting in a glass with excellent glass stability, 1.4, was observed. Thermoluminescence glow curve was observed to be simple with a single well defined dosimetric peak around 200°C. The dose response was found to be linear from 6?µGy to 0.5?kGy when irradiated to Cs-137 gamma rays. Considerably satisfying thermoluminescent (TL) characteristics suggests that the MgB₄O₇ glass could be recommended as a TL dosimeter.     

Theoretical studies and antibacterial activity for Schiff base complexes

New ligand 4‐((2‐Hydroxy1‐naphthyl) methylene amino)‐1.5‐dimethyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐one (HL) was synthesized from the reaction of 2‐hydroxy‐1‐naphthaldehyde and 4‐aminophenaz one. A complexes of this ligand [VO(II)(HL)(SO₄)], [Pt(IV)(L)Cl₃], [Re(V)(L)Cl₃]Cl, and [M(II)(L)Cl] (M═Pd(II), Ni(II), Cu(II)) were synthesized. The resulted compounds were characterized by IR, NMR (¹H and ¹³C), mass spectrometry, element analysis, and UV‐Vis spectroscopy. Additionally, the spectroscopic studies revealed octahedral geometries for the Re(V), Pt(IV) complexes, and square pyramidal for VO(II), square planar for Pd(II) complex, and tetrahedral for the Ni(II) and Cu(II) complexes. Thermodynamic parameters (ΔE^*, ΔH^*, ΔS^*, ΔG^*, and K) were calculated using from the TGA curve Coats‐Red fern method. Therefore, hyper Chem‐8 program has been used to predict structural geometries of compounds in the gas phase. Finally, the synthesized Schiff base and its metal complexes were screened for their biological activity against bacterial species, 2 Gram‐positive bacteria (Bacillus subtilis and Staphylococcus aureus) and 2 Gram‐negative bacteria (Escherichia coli and Pseudomonas aeruginosa).     

Cross‐coupling reactions in water using ionic liquid‐based palladium(II)–phosphinite complexes as outstanding catalysts

Two new phosphinite ligands based on ionic liquids [(Ph₂PO)C₇H₁₄N₂Cl]Cl ( 1 ) and [(Cy₂PO)C₇H₁₄N₂Cl]Cl ( 2 ) were synthesized by reaction of 1‐(3‐chloro‐2‐hydoxypropyl)‐3‐methylimidazolium chloride, [C₇H₁₅N₂OCl]Cl, with one equivalent of chlorodiphenylphosphine or chlorodicyclohexylphosphine, respectively, in anhydrous CH₂Cl₂ and under argon atmosphere. The reactions of 1 and 2 with MCl₂(cod) (M = Pd, Pt; cod = 1,5‐cyclooctadiene) yield complexes cis‐[M([(Ph₂PO)C₇H₁₄N₂Cl]Cl)₂Cl₂] and cis‐[M(Cy₂PO)C₇H₁₄N₂Cl]Cl)₂Cl₂], respectively. All complexes were isolated as analytically pure substances and characterized using multi‐nuclear NMR and infrared spectroscopies and elemental analysis. The catalytic activity of palladium complexes based on ionic liquid phosphinite ligands 1 and 2 was investigated in Suzuki cross‐coupling. They show outstanding catalytic activity in coupling of a series of aryl bromides or aryl iodides with phenylboronic acid under the optimized reaction conditions in water. The complexes provide turnover frequencies of 57 600 and 232 800 h^?1 in Suzuki coupling reactions of phenylboronic acid with p‐bromoacetophenone or p‐iodoacetophenone, respectively, which are the highest values ever reported among similar complexes for Suzuki coupling reactions in water as sole solvent in homogeneous catalysis. Furthermore, the palladium complexes were also found to be highly active catalysts in the Heck reaction affording trans‐stilbenes. Copyright © 2014 John Wiley & Sons, Ltd.     

Recovery and pre-concentration of gold onto poly((N-(Hydroxymethyl)methacrylamide)–1-allyl-2-thiourea) hydrogels synthesized by gamma radiation

Poly((N-(Hydroxymethyl)methacrylamide)–1-allyl-2-thiourea) hydrogels, Poly(NHMMA–ATU), were synthesized by gamma radiation using ⁶⁰Co γ source at different irradiation doses and different ATU content in the irradiated monomer mixture. The swellability of the synthesized hydrogels was changed by irradiation doses and by the content of ATU in the irradiated mixture. These hydrogels were used for the specific gold recovery and pre-concentration from single gold ion solutions and from different natural samples. It has been observed that gold adsorption capacity onto the hydrogels was high at low pHs and reached maximum value at pH = 0.5. Adsorption capacity of the hydrogels for gold at pH = 0.5 was found to be about 698 mg g^− 1 dry hydrogels. Adsorption equilibrium time of gold ions onto the hydrogels was found to be very short and also these hydrogels were showed extremely high selectivity to the gold ions in acidic media when the concentration of the other metal ions were extremely higher than gold. Because of the high specificity of these hydrogels to gold beside the other metal ions at low pHs, all matrix effects were easily eliminated adsorbing gold onto the hydrogels and desorbing into 3 M HCl solution containing 0.8 M thiourea. These hydrogels were found to be highly open pore size. This property of the hydrogels make them attractive due to high adsorption capacity of gold ions on/in the hydrogels penetrating inside and react to all functional groups in the interior surface of the hydrogels.     

Synthesis and characterization of novel 4-nitro-2-(octyloxy)phenoxy substituted symmetrical and unsymmetrical Zn(II), Co(II) and Lu(III) phthalocyanines

Compounds 3 and 4 have been prepared by the reaction of 4-nitrocatechol 1 and 4-nitrophthalonitrile 2 by a common method, aromatic nucleophilic subtitution of the nitro group in 4-nitrophthalonitrile. Starting from 4 and 1-bromooctane, their alkylation reaction gave compound 5. Zn(II) 8, Co(II) 9 and Lu(III) 10 complexes were synthesized from the corresponding metal salts by the tetramerization of compound 5. Compound 7 was prepared by the statistical condensation of 5 and 4,5-bis(hexylthio)phthalonitrile 6 with CoCl₂ · 6H₂O in dry dimethylformamide. The new compounds were characterized by FT-IR, UV/Vis, NMR and mass spectra. The electrochemical properties of the complexes were also investigated by cyclic voltammetry in non-aqueous medium. The effect of temperature on the dc conductivity and the impedance spectra of spin coated film of the compounds was investigated at temperatures between 295 and 433 K and in the frequency range 40–10⁵ Hz. Thermally activated conductivity dependence on temperature was observed for all compounds.     

Preparation, crystal structure, and reactivity of bis {tris(trimethylsilyl) methyl} magnesium

Heating of the lithium magnesate [Li(THF)₂(μ-Br)₂Mg(Tsi)(THF)] (Tsi = (Me₃Si)₃C) under vacuum gives the dialkylmagnesium compound Mg(Tsi)₂, the first two-coordinate magnesium derivative to have been structurally characterized in the solid state. The compound is remarkably thermally stable, not decomposing (or melting) when heated to 350°C. It has a very low reactivity, failing to react in toluene with, for example, CO₂, Me₃SiCl, Me₂SiHCl, MeI, BCl₃ or CH₃COCl, and even with neat CH₃COCl at its boiling point. It does react, though fairly slowly, with I₂ in toluene to give TsiI, and more rapidly with Br₂ to give TsiBr, and with an excess of PhSO₂Cl in toluene at 1OO°C to give TsiCl. It decomposes quickly in the air, and reacts readily with MeOH in toluene to give TsiH without formation of detectable amounts of the intermediate TsiMgOMe, and with O₂ in toluene.     

Chemical and photolytical transformation of biomedically significant compounds in the presence of deuterated solvents

The effect of the nature of solvent on the properties of biomedically important compounds is of particular importance. The conversion of certain biomedical compounds with deuterated solvents is an area of research that has not been accorded adequate recognition in the literature. We explored this area in the interest of shedding some light on the possible effects of solvent on the nature of the solute. The transformation of specific medically important compounds such as bilirubin, thymine, uracil, dehydrocholesterol (7-DHC) and vitamin D(3) was observed in the presence of deuterated solvents such as heavy water and deuterated chloroform. The products of the relevant reactions were confirmed spectrophotometrically. An additional feature to our investigation involved the photolysis of the aforementioned compounds by solar irradiation. The pure samples were dissolved in solutions of the deuterated solvents, corresponding to concentrations of typically 10(-2) mM, and exposed to sunlight for about 15-30 min. The deuterated solvents caused chemical transformation in all chemical compounds tested, and produced intense characteristic absorbance maxima between 200 and 700 nm. Sunlight exposure was also effective in either augmenting the effects of deuterated solvent as in bilirubin and 7-DHC or reducing it as with thymine or having no effect as with uracil or completely changing it as in vitamin D(3). It has been shown that the use of deuterated solvents produces unique chemical and photochemical conversions of bilirubin, 7-DHC, thymine, uracil and vitamin D(3). This was attributed to the fact that deuterated compounds display a somewhat different chemistry to their ordinary counterparts and that possibly thermodynamic considerations could be responsible for the novel transformations.     

Cytotoxic naphthoquinones from Arnebia densiflora (Nordm.) Ledeb and determining new apoptosis inducers

Abstract

In this study, phytochemical composition of Arnebia densiflora (AD) was determined and cytotoxic effects of the n-hexane extract and compounds isolated from this species on various cell lines were investigated. By means of serial chromatographic studies, 6 naphthoquinone derivatives were yielded, which are isovalerylalkannin, α-methyl-n-butyl alkannin, acetylalkannin, β-acetoxy isovalerylalkannin, alkannin and a new compound: 4-hydroxy 4-methyl valeryl alkannin. Structures of the isolated compounds were elucidated using UV, IR, 1D-2D NMR, MS and CD methods. Cytotoxic effects of the extract and isolated alkannins were investigated on L929, HeLa, HEp-2 cells. AD and the isolated compounds demonstrated moderate to strong cytotoxic effects (IC₅₀ range: 4.92-172.35?µg/ml). The results of DNA fragmentation and caspase-3 activity studies on HeLa cells exhibited that AD and the naphthoquinones isolated from it caused cytotoxicity through induction of apoptosis.