Mercury(II) complexes of new bidentate phosphorus ylides: synthesis,spectra and crystal structures

The reaction of dppm (1,1-bis(diphenylphosphino)methane) with 2-bromo-4-phenylacetophenone and benzyl bromoacetate in chloroform produces new phosphonium salts, [Ph₂PCH₂PPh₂CH₂C(O) C₆H₄Ph]Br (I) and [Ph₂PCH₂PPh₂CH₂COOCH₂Ph]Br (II). By allowing the phosphonium salts to react with the appropriate base, the bidentate phosphorus ylides, Ph₂PCH₂PPh₂=C(H)C(O)C₆H₄Ph (III) and Ph₂PCH₂PPh₂=C(H)C(O)OCH₂Ph (IV), were obtained. The reaction of these ligands with mercury(II) halides in dry methanol led to the formation of the mononuclear complexes {HgX₂[(Ph₂PCH₂PPh₂C(H)C(O)C₆H₄Ph)]} (X = Cl (V); X = Br (VI); X = I (VII)) and {HgX₂[(Ph₂PCH₂PPh₂C(H)COOCH₂Ph)]} (X = Cl (VIII); X = Br (IX); X = I (X)). The FTIR and ¹H, ³¹P and ¹³C NMR spectra were studied. The structure of compound III was unequivocally determined by the single-crystal X-ray diffraction technique. Single-crystal X-ray analysis of the {HgBr₂[(Ph₂PCH₂PPh₂C(H)C(O)C₆H₄Me)]} complex (XI) revealed the presence of a mononuclear complex containing the Hg atom in a distorted tetrahedral environment. In all complexes, the ylides referred to above were coordinated through the ylidic carbon and the phosphine atom.     

Quenching effect of deferoxamine on free radical-mediated photon production in luminol and ortho-phenanthroline-dependent chemiluminescence

Removing excessive free radicals （FRs） by a synthetic chemical might give a clue for treatment of many iron-mediated diseases. Deferoxamine （DFO） can be one of the chemicals of choice for the clue. To investigate photoredox properties of DFO, its quenching effect on superoxide radical （O2°）, hydrogen peroxide （H202） and hydroxyl radical （OH~） was examined using luminol and ortho-phenanthroline （o- phen） chemiluminescence （CL） systems and UV-vis spectrophotometry. Stern-Volmer equation was also used for the CL kinetics. The observed quenching effect of DFO on CL]photon production in luminol and o-phen CL systems strongly confirmed the static arm of quenching properties of DFO on OH° and H2O2, but much less pronounced on O2^-°; the quenching property was maximal when iron was involved in the reaction systems. The Stern-Volmer plots in the designed photochemical reaction systems also confirmed a potent quenching effect of DFO on FR-mediated CL. Our study highlights strong photoreducing and antioxidant properties of DFO with huge quenching capacity on excessive FRs, and thus implies its promising prospects for therapeutic applications.     

Ab initio study of Pd-decorated single-walled carbon nanotube with C-vacancy as CO sensor

In this paper, the adsorption of CO onto Pd-decorated (5,5) single-walled carbon nanotube (Pd/SWCNT) and Pd-doped (5,5) single-walled carbon nanotube (Pd/SWCNT-V) has been investigated using ab initio studies. The larger binding energies and charges transfer show that the adsorption of CO onto Pd/SWCNT is more stable than that of CO onto Pd/SWCNT-V. The Pd/SWCNT can be utilized as good sensors for CO molecules due to strong binding energy and large electron charge transfer between the Pd/SWCNT and this molecule. Furthermore, the topological properties of the electron density distributions for intramolecular interactions have been analyzed in terms of the Bader theory of atoms in molecules. Finally, the natural population analysis method has been used to evaluate the Pd–C and Pd/CO interactions.     

Application of Rosin–Rammler model for analysis of CSD in sugar crystallization

Crystal‐size distribution (CSD) is one of the most important parameters in sugar production. The objective is to grow crystals of uniform sizes or narrow CSD. CSD appears to be determined by the growth‐rate history of the crystals and the relative supersaturation (SS) of the solution from which crystals growth takes place. Three methods for preparation of nucleation seeds were described and used for industrial crystallization of raw and white sugars; these are wet milling filtered sugar (ML), agitating saturated solution (AS) and powdered sugars (PD). Rosin–Rammler (RR) and mathematical models were adopted to investigate CSD and the uniformity of the produced crystals. Higher uniformity coefficients were reported for the AS seeded crystals than the other two seeding methods. Furthermore, higher crystal contents were obtained for the AS seeded white sugar batches in comparison.     

Rapid,efficient and selective reduction of aromatic nitro compounds with hydrazine hydrate in the presence of the plain and supported platinum nanoparticles as catalysts

The current study aimed at application of the plain and supported platinum nanoparticles as a heterogenous catalyst for the reduction of aromatic nitro compounds. Monodispersed platinum nanoparticles were synthesized by reduction of H₂PtCl₆ by ethanol in the presence of polyvinyl pyrrolidone as a stabilizer, and then were immobilized on four types of zeolites. The obtained catalyst granules were characterized by X-ray diffractometry and transmission electron microscopy. The study then focused on elaboration of the catalytic activity of the nano catalysts under different operational conditions. It was found that reaction is adequately rapid at ambient temperature, and by utilizing a sufficient amount of catalyst, can be completed in nearly 30 min. Among the utilized zeolitic supports, zeolite 4A had the highest performance, but the mechanism of its synergetic effect on the activity of platinum nano catalyst was not found and requires more investigation.     

Optimization of Pb(II) biosorption by Robinia tree leaves using statistical design of experiments

The present study introduces Robinia tree leaves as a novel and efficient biosorbent for removing Pb(II) from aqueous solutions. In order to reduce the large number of experiments and find the highest removal efficiency of Pb(II), a set of full 2(3) factorial design with two blocks were performed in duplicate (16 experiments). In all experiments, the contact time was fixed at 25 min. The main interaction effects of the three factors including sorbent mass, pH and initial concentration of metal-ion were considered. By using Student's t-test and analysis of variances (ANOVA), the main factors, which had the highest effect on the removal process, were identified. Twenty-six experiments were designed according to Doehlert response surface design to obtain a mathematical model describing functional relationship between response and main independent variables. The most suitable regression model, that fitted the experimental data extremely well, was chosen according to the lack-of-fit-test and adjusted R(2) value. Finally, after checking for possible outliers, the optimum conditions for maximum removal of Pb(II) from aqueous solution were obtained. The best conditions were calculated to be as: initial concentration of Pb(II)=40 mg L(-1), pH 4.6 and concentration of sorbet equal to 27.3 g L(-1).     

Selective Determination of Atropine Using poly Dopamine-Coated Molecularly Imprinted Mn-Doped ZnS Quantum Dots

In this study, a selective method for the determination of atropine in pharmaceutical formulations was proposed. L-cysteine capped Mn-doped ZnS quantum dots (QDs) were prepared in an in-situ method using sodium thiosulfate precursor and characterized by spectrofluorometer, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM) and X-ray diffractometer (XRD). Dopamine hydrochloride was used as a precursor for preparation of poly dopamine-coated molecularly imprinted Mn-doped ZnS quantum dots. Finally, these prepared molecularly imprinted Mn-doped ZnS quantum dots were used for determination of atropine in pharmaceutical formulations. The obtained linear range for determination of atropine was in the range of 2 × 10^?8 – 7 × 10^?6 M, with a correlation coefficient (R²) of 0.9889; and the detection limit (S/N = 3) was 3.2 nM.     

Characterization of hydrocortisone biometabolites and 18S rRNA gene in Chlamydomonas reinhardtii cultures

A unicellular microalga, Chlamydomonas reinhardtii, was isolated from rice paddy-field soil and water samples and used in the biotransformation of hydrocortisone (1). This strain has not been previously tested for steroid bioconversion. Fermentation was carried out in BG-11 medium supplemented with 0.05% substrate at 25 degrees C for 14 days of incubation. The products obtained were chromatographically purified and characterized using spectroscopic methods. 11b,17 beta-Dihydroxyandrost-4-en-3-one (2), 11 beta-hydroxyandrost-4-en-3,17-dione (3), 11 beta,17 alpha,20 beta,21-tetrahydroxypregn-4-en-3-one (4) and prednisolone (5) were the main products of the bioconversion. The observed bioreaction features were the side chain degradation of the substrate to give compounds 2 and 3 and the 20-ketone reduction and 1,2-dehydrogenation affording compounds 4 and 5, respectively. A time course study showed the accumulation of product 2 from the second day of the fermentation and of compounds 3, 4 and 5 from the third day. All the metabolites reached their maximum concentration in seven days. Microalgal 18S rRNA gene was also amplified by PCR. PCR products were sequenced to confirm their authenticity as 18S rRNA gene of microalgae. The result of PCR blasted with other sequenced microalgae in NCBI showed 100% homology to the 18S small subunit rRNA of two Chlamydomonas reinhardtii spp.     

ZSM-5-SO3H as a novel, efficient, and reusable catalyst for the chemoselective synthesis and deprotection of 1,1-diacetates under eco-friendly conditions

Abstract  

ZSM-5 has been modified as supported sulfuric acid (ZSM-5-SO₃H) and introduced for the first time as a mild, convenient, reusable, and heterogeneous catalyst. Various types of aldehydes were efficiently converted to their 1,1-diacetates using a catalytic amount of ZSM-5-SO₃H in excellent yields under solvent-free and heterogeneous conditions at room temperature. The deprotection of 1,1-diacetates has also been achieved using this novel catalyst in ethanol. The procedure is operationally simple, environmentally benign, and only a stoichiometric amount of anhydride is used.     

Effect of shear strain on the α-ε phase transition of iron: a new approach in the rotational diamond anvil cell

The effect of shear strain on the iron α-ε phase transformation has been studied using a rotational diamond anvil cell (RDAC). The initial transition is observed to take place at the reduced pressure of 10.8?GPa under pressure and shear operation. Complete phase transformation was observed at 15.4?GPa. The rotation of an anvil causes limited pressure elevation and makes the pressure distribution symmetric in the sample chamber before the phase transition. However, it causes a significant pressure increase at the centre of the sample and brings about a large pressure gradient during the phase transformation. The resistance to the phase interface motion is enhanced due to strain hardening during the pressure and shear operations on iron and this further increases the transition pressure. The work of macroscopic shear stress and the work of the pressure and shear stress at the defect tips account for the pressure reduction of the iron phase transition.