Mössbauer Spectroscopy and Radiofrequency Absorption Investigations of Pr Substituted 1-2-3 Type Compounds

⁵⁷Fe and ¹⁵¹Eu Mössbauer spectroscopy as well as RF susceptibility measurements were applied to study the effects of Pr substitution either into the rare earth or into the Ba site in Eu_1–x Pr _x Ba₂Cu₃O_7– and EuBa_2–x Pr _x Cu₃O_7–, respectively. Site mixing of Pr between the rare earth and Ba sites could be excluded by the utilization of ⁵⁷Fe Mössbauer spectroscopy. It was found that there exists a correlation between the ¹⁵¹Eu isomer shift and the onset temperature of the superconducting transition independent of the location of Pr. RF susceptibility measurements provide an evidence for a difference in the magnetic moment of Pr substituted for the Eu or Ba sites. The obtained results can be explained by hole filling as the dominant effect of Pr substitution.     

Allylic activation across an Ir–Sn heterobimetallic catalyst: nucleophilic substitution and disproportionation of allylic alcohol

A nucleophilic substitution of allylic alcohols with carbon (arene, heteroarene, allyltrimethylsilane, and 1,3-dicarbonyl compound), sulfur (thiol), oxygen (alcohol), and nitrogen (sulfonamide) nucleophiles has been demonstrated using an in house developed [Ir(COD)(SnCl₃)l(μ-Cl)]₂ heterobimetallic catalyst in 1,2-dichloroethane to afford the corresponding allylic products in moderate to excellent yields. In 4-hydroxycoumarin, allylation occurs at the 3-position. The diaryl-substituted allylic alcohols undergo disproportionation in presence of the heterobimetallic catalyst to provide the corresponding alkenes and chalcones. An electrophilic mechanism is proposed from Hammett correlation study.     

Thin films of Pd and Pd–1% MWCNT as new electrocatalysts for oxidation of phenol in acid medium

Thin films of pure Pd and composite of Pd and 1% multiwalled carbon nanotube have been obtained on glassy carbon electrodes by borohydride reduction method and investigated as electrocatalysts for the oxidation of phenol in acid medium at 25 °C, using cyclic voltammetry (CV), chronopotentiometry, and high-performance liquid chromatography. The CV study showed that both the electrocatalysts are quite stable and active for the phenol oxidation in acid medium. Further, these electrodes do not seem to undergo deactivation due to intermediates and products formed during the phenol oxidation. With the increase in phenol concentration from 2 to 25 mM, the peak current (I _p) increases initially, reaches maximum at about 15 mM, and tends to decrease thereafter. The peak potential (E _p) value was found to be practically unchanged with phenol concentration. The rate for phenol oxidation (I _p) at the surface of both the electrocatalysts increased with the decrease in pH of the reaction mixture. The electrocatalytic activity of the composite electrode was, however, higher than that of pure Pd under similar experimental conditions. Benzoquinone and hydroquinone were identified as the major phenol degradation intermediate products.     

Immobilization and recovery of au nanoparticles from anion exchange resin: resin-bound nanoparticle matrix as a catalyst for the reduction of 4-nitrophenol

The immobilization of gold nanoparticles in anion exchange resin and their quantitative retrieval by means of a cationic surfactant, cetylpyridinium chloride, is studied. The resin-bound gold nanoparticles (R-Au) have been used successfully as a solid-phase catalyst for the reduction of 4-nitrophenol by sodium borohydride. At the end of the reaction, the solid matrix remains activated and separated from the product. The recycling of catalyst particles after the quantitative reduction of 4-nitrophenol and the recovery of gold nanoparticles with unaffected particle morphology from the resin-bound gold nanoparticle entity have been reported.     

Cytotoxic Effect of Microbial Biosurfactants Against Human Embryonic Kidney Cancerous Cell: HEK-293 and Their Possible Role in Apoptosis

Two different microbial biosurfactants S9BS and CHBS were isolated from Lysinibacillus fusiformis S9 and Bacillus tequilensis CH. Cytotoxicity effect of these biosurfactants on human embryonic kidney cancerous cell (HEK-293) were studied with the help of 3-(4,5-dimethylthiazol-2yl-)-2, 5-diphenyl tetrazolium bromide (MTT) assay and morphological changes were observed under inverted microscope. The biosurfactants exhibited positive cytotoxic effect on HEK-293 cell line. It was found that LC₅₀ of S9BS and CHBS were 75 and 100 μg ml^?1, respectively. Further cell cycle and apoptosis analysis of biosurfactant-treated HEK-293 cell line were done by FACS. In this study, cytotoxic effect of glycolipid biosurfactant against HEK-293 cell lines is reported for the first time. Mechanism towards increased membrane permeability of biosurfactant-treated cancer cell may be the incorporation of its lipid moiety into the plasma membrane leading to formation of pores and membrane disruption. Hence, these microbial biosurfactants can prove to be significant biomolecule for cancer treatment.     

新的聚苯乙烯负载锌化合物:高效苯酚氧化催化剂(英文)

The novel recyclable free –ONNO– tetradentate Schiff base ligand N,N′‐bis(2‐hydroxy‐3‐ methox‐ybenzaldehyde)4‐methylbenzene‐1,2‐diamine (3‐MOBdMBn) was synthesized. Complexation of this ligand with zinc(3‐MOBdMBn‐Zn) was performed, and the catalytic activity of the complex was evaluated. The polymer‐supported analog of this complex(P‐3‐MOBdMBn‐Zn) was synthesized, and its catalytic activity was studied. These free and polymer‐anchored zinc complexes were prepared by the reactions of metal solutions with one molar equivalent of unsupported 3‐MOBdMBn or P‐3‐MOBdMBn in methanol under nitrogen. The catalytic activity of 3‐MOBdMBn‐Zn and P‐3‐MOBdMBn‐Zn was evaluated in phenol oxidation. The activity of P‐3‐MOBdMBn‐Zn was signif‐icantly affected by the polymer support, and the rate of phenol conversion was around 50% for polystyrene‐supported 3‐MOBdMBn. The experimental results indicated that the reaction rate was affected by the polymer support, and the rate of phenol conversion was 1.64 μmol/(L·s) in the presence of polystyrene‐supported 3‐MOBdMBn.     

Influence of Confined Water on the Photophysics of Dissolved Solutes in Reverse Micelles

The photophysical parameters of two probes with largely different hydrophobic character, namely, coumarin 1 and coumarin 343, are investigated in sodium bis‐(2‐ethylhexyl)sulfosuccinate (AOT)/hexane/water reverse micelles at various water/AOT molar ratio w₀. Correlation of photophysical parameters such as fluorescence quantum yield, fluorescence lifetime, and emission maxima with w₀ indicate distinctly different trends below and above w₀≈7 for both probes. The variation of the average rotational correlation times obtained from fluorescence anisotropy decays for both probes in reverse micelles further corroborate the above observation. Similar studies were also performed in nonaqueous reverse micelles with acetonitrile as polar solvent. Similar to aqueous reverse micelles, breaks in the photophysical parameters with increasing acetonitrile/AOT molar ratios w′₀ were also observed in these cases, although at a much lower w′₀ value of 3. The present results indicate that around w₀≈7 for aqueous reverse micelles (and around w′₀≈3 for nonaqueous reverse micelles) a distinct change occurs in the probe microenvironment, which is rationalized on the basis of the relative populations of interfacial and core water. We propose that until the ionic head groups and counterions are fully solvated by polar solvents, that is, up to w₀≈7 (or w′₀≈3), the interfacial water population dominates. Above these molar ratios coalescence of excess water molecules with each other to form truncated H‐bonded water clusters leads to a sizable population of core water. This is further substantiated by changes in the IR absorption spectra for the O? D stretching mode of diluted D₂O in reverse micelles with varying w₀. Critical comparison of the present results with relevant literature reports provide clear support for the proposals made on water structure in reverse micelles. The role of relative size of the probe and the reverse micelles for differences in polar solvent to AOT ratios (w₀=7 and w′₀=3) in the observed breaks in the two types of reverse micelles is also discussed.     

Synthesis, spectroscopic studies of new water-soluble Co(II) and Cu(II) macrocyclic complexes of 4,15-bis(2-hydroxyethyl)-2,4,6,13,15,17-hexaazatricyclodocosane: their interaction studies with calf thymus DNA and guanosine 5′ monophosphate

New water soluble Co(II) 1, Ni(II) 2 and Cu(II) 3 complexes of 4,15-bis(2-hydroxyethyl)-2,4,6,13,15,17-hexaazatricyclodocosane Co(II) were synthesized and characterized by various techniques, viz. elemental analysis, conductivity measurements, infrared, electronic, ESI-MS, ¹H and ¹³C NMR spectroscopy. Molar conductance measurements in aqueous solution showed that complexes 1, 2 and 3 are ionic in nature. On the basis of spectroscopic data, a square planar geometry was assigned to the complexes involving four N-atoms of the two cyclohexane moieties. Interaction studies of 1 and 3 with CT-DNA were carried using UV/Visible absorption spectroscopy, fluorescence spectrophotometry, cyclic voltammetry and viscosity measurements. Absorption spectral traces reveal 27.7 and 23.3% hyperchromism for complexes 1 and 3, respectively indicative of strong binding to CT-DNA. These results were authenticated by fluorescence quenching experiments and viscosity measurements. The intrinsic binding constants K _b of 1 and 3 are 2.94 × 10⁴ and 2.71 × 10⁴ M^?1, respectively. Early transition metals show preference for O6 position while later ones copper and cobalt prefer N7 position of DNA base guanine. To validate this hypothesis, interaction studies of copper (II) and cobalt (II) complexes were carried out with 5′GMP, which revealed electrostatic interactions are more favored along with hydrogen bonding than coordinate covalent interaction to N7 position of guanine.