Synthesis of new imines and amines containing organosilicon groups

The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyl lithium, (Me₃Si)₃CLi, in THF at 0 °C gives 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde (1) and 4,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene (2). The new aldehyde (1) reacts with variety of amines in ethanol to afford the corresponding imines (3) containing vinylbis(trimethylsilyl) group. The newly synthesized imines (3) can be completely converted into amines containing vinylbis(trimethylsilyl) group with an excess amount of NaBH₄. In the case of N-[4-(2,2-bis(trimethylsilyl)ethenyl)benzyl]-2,6-dimethylaniline LiAlH₄ was used as a reducing agent in THF.     

Optimization of dispersive liquid-liquid microextraction coupled with inductively coupled plasma-optical emission spectrometry with the aid of experimental design for simultaneous determination of heavy metals in natural waters

In this study, dispersive liquid-liquid microextraction (DLLME) combined with inductively coupled plasma optical emission spectrometry (ICP-OES) was developed for simultaneous preconcentration and trace determination of chromium, copper, nickel and zinc in water samples. Sodium diethyldithiocarbamate (Na-DDTC), carbon tetrachloride and methanol were used as chelating agent, extraction solvent and disperser solvent, respectively. The effective parameters of DLLME such as volume of extraction and disperser solvents, pH, concentration of salt and concentration of the chelating agent were studied by a (2^f−1) fractional factorial design to identify the most important parameters and their interactions. The results showed that concentration of salt and volume of disperser solvent had no effect on the extraction efficiency. In the next step, central composite design was used to obtain optimum levels of effective parameters. The optimal conditions were: volume of extraction solvent, 113 μL; concentration of the chelating agent, 540 mg L⁻¹; and pH, 6.70. The linear dynamic range for Cu, Ni and Zn was 1-1000 μg L⁻¹ and for Cr was 1-750 μg L⁻¹. The correlation coefficient (R²) was higher than 0.993. The limits of detection were 0.23-0.55 μg L⁻¹. The relative standard deviations (RSDs, C = 200 μg L⁻¹, n = 7) were in the range of 2.1-3.8%. The method was successfully applied to determination of Cr, Cu, Ni and Zn in the real water samples and satisfactory relative recoveries (90-99%) were achieved.     

Quantum chemical and theoretical kinetics study of the O(3P) + CS2 reaction

The triplet potential energy surface of the O((3)P) + CS(2) reaction is investigated by using various quantum chemical methods including CCSD(T), QCISD(T), CCSD, QCISD, G3B3, MPWB1K, BB1K, MP2, and B3LYP. The thermal rate coefficients for the formation of three major products, CS + SO ((3)Σ(-)), OCS + S ((3)P) and CO + S(2) ((3)Σ(-)(g)) were computed by using transition state and RRKM statistical rate theories over the temperature range of 200-2000 K. The computed k(SO + CS) by using high-level quantum chemical methods is in accordance with the available experimental data. The calculated rate coefficients for the formation of OCS + S ((3)P) and CO + S(2) ((3)Σ(-)(g)) are much lower than k(SO + CS); hence, it is predicted that these two product channels do not contribute significantly to the overall rate coefficient.     

Metal matrix composites for sustainable lotus-effect surfaces

The lotus effect involving roughness-induced superhydrophobicity is a way to design nonwetting, self-cleaning, omniphobic, icephobic, and antifouling surfaces. However, such surfaces require micropatterning, which is extremely vulnerable to even small wear rates. This limits the applicability of the lotus effects to situations when wear is practically absent. To design sustainable superhydrophobic surfaces, we suggest using metal matrix composites (MMCs) with hydrophobic reinforcement in the bulk of the material, rather than only at its surface. Such surfaces, if properly designed, provide roughness and heterogeneity needed for superhydrophobicity. In addition, they are sustainable, since when the surface layer is deteriorated and removed due to wear, hydrophobic reinforcement and roughness remains. We present a model and experimental data on wetting of MMCs. We also conducted selected experiments with graphite-reinforced MMCs and showed that the contact angle can be determined from the model. In order to decouple the effects of reinforcement and roughness, the experiments were conducted for initially smooth and etched matrix and composite materials.     

Improved sensitivity of intensity-modulated spectroscopy using correlative signal processing

Frequency-modulation (FM) spectroscopy is known to be a sensitive spectroscopic technique capable of accurately measuring the frequency dependence of the absorption and index of refraction of narrow spectral features. The absorption and index of refraction are coupled by a form of the Kramers-Kronig (K-K) relations, and both components provide information about the spectral feature. In this Letter, we propose a processing technique based on fitting the data to a complex signal model derived from the K-K relation. By using this complex constraint and only processing a single quadrature, our model predicts significant improvement in the minimum detectable absorption compared with conventional FM spectroscopy.     

Sonochemical synthesis, size controlling and gas sensing properties of NiO nanoparticles

Nanoparticles of NiO (NP-NiO) were prepared by a novel sonochemical route from Ni acetate and sodium hydroxide without any requirement of calcinations steps at high temperature and without surfactants. Drop casting of the nanocrystals onto alumina substrates allowed the fabrication of gas sensing devices, which were tested towards NO₂ and CO and showed promising results. At low working temperature, the NiO nanoparticles based sensors are selective to nitrogen oxide; in fact a good sensitivity is shown at 200 °C at low concentration (2 ppm), while at temperature above 350 °C, high responses are obtained for carbon monoxide. The results obtained are stimulating for further developing of NP-NiO based sensor devices.     

Nano-ferrous ferric oxide (nano-Fe3O4): Powerful,reusable, and stable catalyst for N-Boc protection of amines

Nano-ferrous ferric oxide (nano-Fe₃O₄) efficiently catalyzed N-boc protection of amines in high yields and acceptable reaction times. Nano-Fe₃O₄ was applied as an efficient, green, heterogeneous and reusable magnetite catalyst. Clean reaction, simple purification, short reaction time and high yield were some other advantages of this compound.     

Iron(III) hetero-ligand complexes containing 1,10-phenanthroline derivatives, chloride and dimethyl sulfoxide: synthesis, characterization, crystal structure determination and luminescent properties

[Fe(Me-phen)Cl₄][Me-phen·H] (1) and [Fe(Cl-phen)Cl₄][Cl-phen·H] (2) complexes were prepared from the reactions of FeCl₃·6H₂O with 5-methyl-1,10-phenanthroline (Me-phen) and 5-chloro-1,10-phenanthroline (Cl-phen), respectively, in a 0.1 M aqueous solution of HCl. Stepwise addition of dimethyl sulfoxide to the solution of 1 in methanol results in a mixed ligand complex, [Fe(Me-phen)Cl₃(DMSO)] (3). Complex 3 was also prepared by two other methods. The reaction of a methanol solution of [Fe(Me-phen)Cl₄][Me-phen·H] (1) with [Fe(DMSO)₄Cl₂][FeCl₄] in 1:6 ratio led to 3. Complex 3 was also prepared from the reaction of 5-methyl-1,10-phenanthroline with [Fe(DMSO)₄Cl₂][FeCl₄] in 1:1 ratio in methanol. The three complexes were characterized by IR, UV–Vis, ¹H NMR and luminescence spectroscopy and their structures were studied by the single-crystal diffraction method. Calculation methods were employed to study the isomerization of (3) in solution.     

COMMON FIXED POINT THEOREMS FOR THREE MAPS IN DISCONTINUOUS Gb-METRIC SPACES

In [Aghajani A, Abbas M, Roshan JR. Common fixed point of generalized weak contractive mappings in partially ordered Gb-metric spaces. Filomat, 2013, in press], using the concepts of G-metric and b-metric Aghajani et al. defined a new type of metric which is called generalized b-metric or Gb-metric. In this paper, we prove a common fixed point theorem for three mappings in Gb-metric space which is not continuous. An example is presented to verify the effectiveness and applicability of our main result.     

Common fixed point theorems for three maps in discontinuous Gb metric spaces

In [Aghajani A, Abbas M, Roshan JR. Common fixed point of generalized weak contractive mappings in partially ordered G_b-metric spaces. Filomat, 2013, in press], using the concepts of G-metric and b-metric Aghajani et al. defined a new type of metric which is called generalized b-metric or G_b-metric. In this paper, we prove a common fixed point theorem for three mappings in G_b-metric space which is not continuous. An example is presented to verify the effectiveness and applicability of our main result.