The Radical Cationic Repair Pathway of Cyclobutane Pyrimidine Dimer: The Effect of Sugar‐Phosphate Backbone

Radical cationic repair process of cis–syn thymine dimer has been investigated when (1) sugar‐phosphate backbones were substituted by hydrogen atoms, (2) phosphate group was substituted by two hydrogen atoms each on a sugar ring and (3) sugar‐phosphate backbone was taken into account. The effect of the interactions between N1 and N1′ lone pairs and the C6‐C6′ antibonding orbital are the most important evidences for the cleavage of the C6‐C6′ bond in the first step of radical cationic repair mechanism in the absence of the sugar‐phosphate backbone. The impact of the N1 and N1′ lone pairs on the C6‐C6′ bond cleavage decreases and the energy barrier of the cleavage of that bond significantly increases in the presence of the deoxynucleoside sugars and the sugar‐phosphate backbone.     

Green Procedure for the Synthesis of Phthalazino[2,3‐b]phthalazine‐5,7,12,14‐tetraones

Different novel phthalazino[2,3‐b]phthalazine‐5,7,12,14‐tetraones were synthesized in a simple and environmentally benign method from the reaction of phthalic anhydrides with semicarbazide or thiosemicarbazide using montmorillonite K‐10 clay as solid heterogeneous acidic catalyst and microwaves under solvent‐free conditions in good yields and short reaction times. Products were characterized by the elemental analysis, IR, NMR, and mass spectrometry.     

A new molecularly imprinted polymer for selective extraction and pre‐concentration of guaifenesin in different samples: Adsorption studies and kinetic modeling

This paper describes the synthesis of a molecularly imprinted polymer by chemical oxidation of pyrrole as the functional monomer, and at the presence of guaifenesin as the template. The prepared polymer was used as adsorbent in molecularly imprinted solid‐phase extraction followed by spectrophotometric determination. Different parameters in the solid‐phase extraction including sample pH, adsorbent weight, washing solution, and elution solvent were studied to determine optimum conditions for isolation and enrichment of guaifenesin. The results showed guaifenesin was quantitatively adsorbed on the molecularly imprinted polymer at pH 6.0 and completely eluted with an ethanol–water solution (50% v/v). An enrichment factor of four with satisfactory recoveries (87.0–95.0%) was obtained. The solid‐phase extraction columns could be used for up to six consecutive elution‐loading cycles without significant decreases in the analyte recoveries. The method had a dynamic range of 3.0 × 10^?6–1.5 × 10^?4 mol/L with a limit of detection and limit of quantification of 1.4×10^?6 and 4.5×10^?6 mol/L, respectively. The proposed procedure was used for the extraction and determination of guaifenesin in different pharmaceutical formulations, with satisfying results being achieved.     

Study of complexation process between 4′-nitrobenzo-15-crown-5 and yttrium(III) cation in binary mixed non-aqueous solvents using conductometric method

The complexation reaction of macrocyclic ligand (4??-nitrobenzo-15C5) with Y³⁺ cation was studied in acetonitrile-methanol (AN-MeOH), acetonitrile-ethanol (AN-EtOH), acetonitrile-dimethylformamide (AN-DMF) and ethylacetate-methanol (EtOAc-MeOH) binary mixtures at different temperatures using conductometry method. The conductivity data show that in all solvent systems, the stoichiometry of the complex formed between 4??-nitrobenzo-15C5 and Y³⁺ cation is 1: 1 (ML). The stability order of (4??-nitrobenzo-15C5). Y³⁺ complex in pure non-aqueous solvents at 25°C was found to be: EtOAc > EtOH > AN ?? DMF > MeOH, and in the case of most compositions of the binary mixed solvents at 25°C it was: AN??MeOH ?? AN-EtOH > AN-DMF > EtOAc-MeOH. But the results indicate that the sequence of the stability of the complex in the binary mixed solutions changes with temperature. A non-linear behavior was observed for changes of logK _f of (4??-nitrobenzo-15C5 · Y³⁺) complex versus the composition of the binary mixed solvents, which was explained in terms of solvent-solvent interactions and also the hetero-selective solvation of the species involved in the complexation reaction. The values of thermodynamic parameters (??H _c ^? and ??S _c ^? ) for formation of the complex were obtained from temperature dependent of the stability constant using the van??t Hoff plots. The results represent that in most cases, the complex is both enthalpy and entropy stabilized and the values and also the sign of thermodynamic parameters are influenced by the nature and composition of the mixed solvents.     

Green and mild laccase-catalyzed aerobic oxidative coupling of benzenediol derivatives with various sodium benzenesulfinates

The oxidative coupling reaction between hydroquinone or catechols and various sodium benzenesulfinates was investigated using the laccase from Trametes versicolor, in the presence of O₂ in a phosphate buffer solution at room temperature to afford sulfonyl benzenediols in 75–95% yield.     

Microstructure of nickel nanoparticles embedded in carbon films: case study on annealing effect by micromorphology analysis

The presented study is aimed at analyzing the surface texture of amorphous hydrogenated carbon layers containing nickel nanoparticles (Ni‐NPs@a‐C:H) within their structure, which were deposited by Radio Frequency (RF) sputtering and RF‐Plasma Enhanced Chemical Vapor Deposition (RF‐PECVD) methods on glass substrates. Prepared films were then used as research material following their annealing at two different temperatures of 250 °C and 350 °C in an inert argon atmosphere. Series of height samples were taken with the help of atomic force microscopy (AFM) operating in a non‐contact mode and examined in order to determine their fractal characteristics. Raw AFM data were first plane‐fitted to remove the surface bow exhibiting the so‐called residual surface, and then numerically processed to calculate the Areal Autocorrelation Function (AACF), which was later used to compute the Structure Function (SF). The log–log plots of the latter served for calculation of fractal properties of surfaces under investigation, including fractal dimension D, and pseudo‐topothesy K. The analysis of 3‐D surface texture helps to understand their essential characteristics and their implications as well as graphical models and their implementation in computer simulation. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and characterization of novel optically active poly(amide-imide)s and poly(ester-imide)s containing calix[4]arene and amino acid units with binding ability towards alkali metal and toxic heavy metal cations

<正>A novel calix[4]arene derivative 2 with amino functional groups at the lower rim was first prepared via introduction of nitro functional groups and amination of the dinitro derivative of calix[4]arene.The optically active monomers were synthesized by dehydration of L-leucine(and L-isoleucine) and 3,3',4,4'-benzophenonetetracarboxylic- 3,3',4,4'-dianhydride(3) followed by reaction with thionyl chloride to form 5a and 5b.Two methods,polymerization under microwave irradiation and solution polymerization in CH_2Cl_2/TEA,were then employed to carry out the condensation polymerization of 2 with the optically active monomers 5a and 5b,respectively.The polymerization conditions affected the kind of resulting polymers,poly(amide-imide)s(PAIs) 6a and 6b and poly(ester-imide)s(PEIs) 6a' and 6b' were obtained selectively in good yields and moderate inherent viscosities.Sorption-extraction experiments were carried out using cram picrate extraction method and verified good binding ability of the resulting calixarene-based polymers towards silver,alkali metal and toxic heavy metal cations.Also thermogravimetric analysis indicated that the resulting PAIs and PEIs were thermally stable.     

ZnO thin film characterization by X-ray reflectivity optimization using genetic algorithm and Fourier transformation

Zinc oxide (ZnO) thin film was fabricated by sol-gel spin coating method on glass substrate. X-ray reflectivity (XRR) and its optimization have been used for characterization and extracting physical parameters of the film. Genetic algorithm (GA) has been applied for this optimization process. The model independent information was needed to establish data analyzing process for X-ray reflectivity before optimization process. Independent information was exploited from Fourier transform of Fresnel reflectivity normalized X-ray reflectivity. This Fourier transformation (Auto Correlation Function) yields thickness of each coated layer on substrate. This information is a keynote for constructing optimization process. Specular X-ray reflectivity optimization yields structural parameters such as thickness, roughness of surface and interface and electron density profile of the film. Acceptable agreement exists between results obtained from Fourier transformation and X-ray reflectivity fitting.