Inclusion complexes of cryptophane-E with dichloromethane and chloroform: A thermodynamic and kinetic study using the 1D-EXSY NMR method

Complexation equilibria and kinetics of exchange of chloroform and dichloromethane molecules between the cavity of cryptophane-E and bulk solution were investigated using NMR methods. Using one-dimensional magnetization transfer (1D-EXSY type sequence), chemical exchange rates were measured in different temperature ranges, limited by the equilibrium constant values of the complexes and the boiling points of the guest substances. From the kinetic data, activation energies were calculated using the Arrhenius equation. From the temperature-dependence of the association constant data, the enthalpy and entropy of complexation were estimated and compared with values for similar complexes of other cryptophanes.     

Determination of ticagrelol in rat plasma and tablets by micellar electrokinetic chromatography coupled with large volume sample stacking: Application to a pharmacokinetic study

A method using micellar electrokinetic chromatography coupled with large-volume sample stacking for the determination of ticagrelol was developed and validated. The analysis was performed in a fused silica capillary (41.5 cm effective length, 50 μm diameter) with ultraviolet detection at 195 nm. The background electrolytes were 30 mM phosphate buffer of pH 3.0 with 120 mM sodium dodecylsulfate and 10 % (v/v) acetonitrile (120 s X 50 mbar; 20°C; -18 kV) and 30 mM borate buffer of pH 8.5 with 75 mM sodium dodecylsulfate (120 s X 50 mbar; 20°C; 25 kV); under acidic and alkaline conditions, respectively. The method was found to be reliable with respect to specificity, linearity of the calibration line (R² > 0.99), repeatability (relative standard deviation 2.56%–3.34%), and accuracy (recovery in the range 101.21%–102.67%). The limits of detection and quantitation were 0.032, 0.071, and 0.087, 0.188 μg/mL, respectively. The method was successfully applied for the determination of ticagrelol concentrations in rat plasma and tablets with good recoveries and reproducibility. The presented method proved to be suitable for monitoring ticagrelor in rat plasma.     

Preparation of immobilized hexamine on Fe3O4/SiO2 core/shell nanoparticles: a novel catalyst for solvent-free synthesis of bis(indolyl)methanes

Research on Chemical Intermediates - Hexamethylenetetramine covalently immobilized on silica-coated magnetic nanoparticles is prepared and characterized by XRD, FT-IR, SEM, and VSM. According to...     

Application of chemometric methods in modeling of competitive multidye biosorption from ternary system

Simultaneous biosorption properties of three cationic dyes (Methylene blue, Crystal violet and Safranin) on Sargassum glaucescens were studied. In the most of previous papers in the field of dye biosorption, one dye or dyes with nearly separate spectra were used and dye concentration was determined by Beer’s law at different λ _max. Significant of this study is application of dyes with highly overlapped spectra (as many real situations) that their concentrations can be determined by chemometric methods. Plackett–Burman design was applied to identify the most significant factors, Box–Behnken design was used to determine optimal conditions, and principal component-wavelet neural network was used for the simultaneous determination of dye concentrations in ternary solutions. The optimum biosorption conditions were determined as dye concentration 10^?4 mol L^?1, biosorbent dosage 0.1 g L^?1 and biosorbent particle size 0.188 µm. At this condition, maximum biosorption capacity was 0.80 mmol g^?1. The biosorption process was slightly slower in the ternary system comparing with single system which was related to competition phenomena between dyes. It was found that the overall biosorption data were described by the pseudo-second-order kinetic model. Fourteen isotherm models were applied to experimental data, and it was concluded that Hill model had the best correlation.     

Chloro/bromotrimethylsilane-Cu(NO3)2·3H2O: Safe and efficient reagent system for the decarboxylative ipso-nitration and dibromination of cinnamic acids

Further synthetic potential of halotrimethylsilane-nitrate salt mixture is revealed. A mixture of TMSX-Cu(NO₃)₂·3H₂O system is found to be an efficient reagent system for both the decarboxylative nitration (ipso-nitration) when X = Cl, and dibromination of cinnamic acids, with X = Br, under mild conditions. The reactions are safe and simple, affording the corresponding products (E)-β-nitrostyrenes, and anti-2,3-dibromo-3-phenylpropanoic acids in high yields with high selectivity in a relatively short time. Use of hazardous and toxic nitrating systems such as acetyl nitrate and brominating agents such as molecular bromine can be avoided.     

Enhanced spectroscopic properties and Judd–Ofelt parameters of Er-doped tellurite glass: Effect of gold nanoparticles

Glasses with composition 70TeO₂–20ZnO–10Na₂O–0.5Er₂O₃–(x)Au are synthesized by melt-quenching technique. Their spectroscopic and optical characterizations are made. The presence of gold nanoparticles (Au NPs) with average size ～9 nm is confirmed from TEM micrograph. The value of E_dir is found to lie between 3.082 and 3.073 eV, while E_indir lies within 2.765 to 2.724 eV. The observed visible up-conversion (UC) emission under 779 nm excitation wavelength exhibits two bands centered at 546 nm (green) and 637 nm (red) in all samples. The glass with 0.4 mol% Au NPs shows dominant enhancement in the UC emission intensity of the order of 3.5 times for the green band (⁴S_3/2 → ⁴I_15/2) and a weaker enhancement for the red (⁴F_9/2 → ⁴I_15/2) band. The optical properties of the system are affirmed to depend strongly on the Au concentration in the dielectric medium. The absorption spectra consist of six bands attributed to absorption from ground state (⁴I_15/2) to ⁴I_13/2, ⁴I_11/2, ⁴I_9/2, ⁴F_9/2, ²H_11/2, and ⁴F_7/2 excited states. The structural reveals that the types of bonding and difference in electro-negativity can be manipulated by the presence of metallic NPs in glass matrix. Judd–Ofelt analysis asserts the increase in Ω₂ and Ω₆ parameters with the addition of Au NPs and the enhancement of green and red emissions. The enhancement is mainly attributed to large plasmonic effect of Au NPs. The proposed glasses can be nominated as potential materials for solid state laser developments.     

Sonochemically synthesis of pyrazolones using reusable catalyst CuI nanoparticles that was prepared by sonication

A simple and green process to prepare copper iodide in nano scale via sonication was carried out. Subsequently, this nanoparticles was used as an efficient catalyst for the synthesis of 2-aryl-5-methyl-2,3-dihydro-1H-3-pyrazolones via four-component reaction of hydrazine, ethyl acetoacetate, aldehyde and β-naphthol in water under ultrasound irradiation. The combinatorial synthesis was attained for this procedure with applying ultrasound irradiation while making use of water as green ambient. Simple work-up, excellent yield of products and short reaction times are some of the important features of this protocol. Notably, this catalyst could be recycled and reused for five times without noticeably decreasing the catalytic activity.     

A Note on the Roman Bondage Number of Planar Graphs

A Roman dominating function on a graph G = (V(G), E(G)) is a labelling ${f : V(G)\rightarrow \{0,1,2\}}$ satisfying the condition that every vertex with label 0 has at least a neighbour with label 2. The Roman domination number γ _R (G) of G is the minimum of ${\sum_{v \in V(G)}{f(v)}}$ over all such functions. The Roman bondage number b _R (G) of G is the minimum cardinality of all sets ${E\subseteq E(G)}$ for which γ _R (G \ E) > γ _R (G). Recently, it was proved that for every planar graph P, b _R (P) ≤ Δ(P) + 6, where Δ(P) is the maximum degree of P. We show that the Roman bondage number of every planar graph does not exceed 15 and construct infinitely many planar graphs with Roman bondage number equal to 7.     

Prediction of different antibacterial activity in a new set of formyl hydroxyamino derivatives with potent action on peptide deformylase using structural information

Due to the essential role of peptide deformylase (PDF) at the bacterial growth cycle, it is a noteworthy target for developing a novel antibacterial agent. In the current study, the antibacterial activities of a set of 44 new structures of formyl hydroxyamino derivatives as PDF inhibitors were quantified using quantitative structure–activity relationship (QSAR). Artificial neural networks (ANN) were used as a chemometrics tool for QSAR modeling. Three quantitative models were suggested to relate the chemical structural features of the formyl hydroxyamino derivatives to their antibacterial activities (pIC₅₀) against Staphylococcus aureus, methicillin-susceptible S. aureus (MSSA), and methicillin-resistant S. aureus (MRSA) peptide deformylase. The sufficiency of the model for prediction of the antibacterial activities of the desired PDF inhibitor compounds against S. aureus, MSSA, and MRSA was statistically demonstrated according to the validation parameters such as coefficient of determination (R²), mean square error (MSE) in training, validation, and prediction sets, and also using applicability domain (AD) and randomization test.

     

Effect of Nickel Distributions Embedded in Amorphous Carbon Films on Transport Properties

Electrical properties of C/Ni films are studied using four mosaic targets made of pure graphite and stripes of nickel with the surface areas of 1.78,3.21,3.92 and 4.64%.The conductivity data in the temperature range of400–500 K shows the extended state conduction.The conductivity data in the temperature range of 150–300 K shows the multi-phonon hopping conduction.The Berthelot-type conduction dominates in the temperature range of 50–150 K.The conductivity of the films in the temperature range about 50 K is described in terms of variable-range hopping conduction.In low temperatures,the localized density of state around Fermi level(F)for the film deposition with 3.92% nickel has a maximum value of about 56.2×10~(17)cm~(-3)eV~(-1) with the minimum average hopping distance of about 3.43 × 10~(-6) cm.