Synthesis of a new 1,2,3,4,5‐pentasubstituted cyclohexanol and determining its stereochemistry by NMR spectroscopy and quantum‐chemical calculations

The presence of substituents in cyclohexane can influence to the ratio of conformers; for some cases, the boat form is preferable. The new six‐membered cyclohexanol derivative 2 has been obtained by the synthesis of (E)‐1‐(bromophenyl)‐3‐phenylpropen‐2‐one ( 1 ). The NMR and quantum‐chemical conformational analysis for the 2 have carried out, and its possible mechanism of formation was given. Copyright © 2015 John Wiley & Sons, Ltd.     

Leaching of Celestite with Sodium Sulfide

Leaching of celestite mineral, SrSO₄, with sodium sulfide, Na₂S, was investigated from the point of strontium carbonate, SrCO₃, production. Experiments were carried out to explain the conversion mechanism of celestite to strontium disulfide, SrS₂, in Na₂S solution. Effects of stirring speed, particle size, and concentration of Na₂S on conversion were studied at constant temperature and solid‐to‐liquid ratio. The results showed that the rate of conversion mainly depends on Na₂S concentration. It was concluded that leaching of celestite in Na₂S solution for conversion to SrS₂ is possible but slow.     

Synthesis and Characterization of New Nickel(II) Chelates With S-Alkyl-Salicylaldehyde Thiosemicarbazones

Abstract

The template reactions of salicylidene-, 5-bromosalicylidene-, and 3,5-dichlorosalicylidene-S-R-thiosemicarbazone (R: propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, dodecyl) with 5-bromo- and 3,5-dichlorosalicylaldehyde in the presence of nickel(II) yielded N¹,N⁴-diarylidene-S-alkyl-thiosemicarbazone chelates. The N₂O₂ type complexes were isolated as stable solid compounds and characterized by elemental analysis, electronic, infrared, ¹H NMR, and mass spectroscopies. The magnetic susceptibility measurements at room temperature (r.t.) indicate the diamagnetic nature of the complexes. The relationship between melting point (mp) values of the nickel(II) template complexes and the chain length of alkyl moiety was clearly shown.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the related elements to view the free supplemental file.     

New Amperometric Cholesterol Biosensors Using Poly(ethyleneoxide) Conducting Polymers

Accumulation of cholesterol in human blood can cause several health problems such as heart disease, coronary artery disease, arteriosclerosis, hypertension, cerebral thrombosis, etc. Therefore, simple and fast cholesterol determination in blood is clinically important. In this study, two types of amperometric cholesterol biosensors were designed by physically entrapping cholesterol oxidase in conducting polymers; thiophene capped poly(ethyleneoxide)/polypyrrole (PEO-co-PPy) and 3-methylthienyl methacrylate-co-p-vinyl benzyloxy poly(ethyleneoxide)/polypyrrole (CP-co-PPy). PEO-co-PPy and CP-co-PPy were synthesized electrochemically and cholesterol oxidase was immobilized by entrapment during electropolymerization. The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H₂O₂ at +0.7 V in the absence of a mediator. Kinetic parameters, such as Km and Imax, operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. Km values were found as 1.47 and 5.16 mM for PEO-co-PPy and CP-co-PPy enzyme electrodes, respectively. By using these Km values, it can be observed that ChOx immobilized in PEO-co-PPy shows higher affinity towards the substrate.     

Molecular dynamics simulation study of the structural features and inclusion capacities of cucurbit[6]uril derivatives in aqueous solutions

Molecular dynamics (MD) simulations were performed for cucurbit[6]uril (CB6) methyl and cyclohexyl derivatives in aqueous solutions. Furthermore, MD simulations have been conducted to study the inclusion complexes between each CB6 derivative with α,ω-pentane diammonium ion (NH₃⁺(CH₂)₅NH₃⁺) to estimate the binding free energies, the complex geometries and the intermolecular forces responsible for complex formation. Results show a complete inclusion of the guest molecule in the cavity of the host for all complexes. Results also indicate that the guest dynamics inside the cavity of the substituted host is similar to that for the unsubstituted host. This demonstrates that the molecular recognition of the host is not affected by the alkyl substitution at the equator. Also, there is an insignificant conformational change of the macrocyclic structure upon inclusion of the guest. Molecular mechanics/Poisson Boltzmann surface area method was used to estimate the binding free energy of each complex. Results indicate that host–guest electrostatic interactions make the largest contribution to the complex binding free energy. Moreover, van der Waals interactions add significantly to the complex stability. The guest molecules show more or less similar binding free energies with the substituted CB6 that exhibits slightly more negative values than unsubstituted CB6 which is proved also by umbrella sampling.     

Fast-scan vs conventional differential scanning calorimetry (DSC) techniques in detection of crystallization events of tolbutamide–polyethylene glycol composite

This study investigated the capacity of fast-scan (400 °C min^?1) against conventional (10 °C min^?1) differential scanning calorimetry (DSC) techniques to track crystallization phenomenon in tolbutamide–polyethylene glycol 3000 composites prepared by hot melt method (mass ratios 1:1, 1:5, and 1:9) and stored at 25 and 75 % relative humidities. Drug crystallization in composites was indicated by X-ray diffractometry (XRD) and scanning electron microscopy characterization over 40 days storage. With reference to XRD as gold measurement standard, fast-scan DSC could not map the crystallization events of composites (Pearson correlation: fast-scan DSC peak temperature and enthalpy versus XRD peak intensity and area, p > 0.05). Conventional DSC was able to indicate marked drug crystallization through an increase in endothermic enthalpy value of peaks at high temperature regimes between 250 and 360 °C due to formation of high melting point crystal form.     

Design,Synthesis, and Biological Evaluation of Pyridazinones Containing the (2-Fluorophenyl) Piperazine Moiety as Selective MAO-B Inhibitors

Twelve pyridazinones (T1–T12) containing the (2-fluorophenyl) piperazine moiety were designed, synthesized, and evaluated for monoamine oxidase (MAO) -A and -B inhibitory activities. T6 was found to be the most potent MAO-B inhibitor with an IC₅₀ value of 0.013 µM, followed by T3 (IC₅₀ = 0.039 µM). Inhibitory potency for MAO-B was more enhanced by meta bromo substitution (T6) than by para bromo substitution (T7). For para substitution, inhibitory potencies for MAO-B were as follows: -Cl (T3) > -N(CH₃)₂ (T12) > -OCH₃ (T9) > Br (T7) > F (T5) > -CH₃ (T11) > -H (T1). T6 and T3 efficiently inhibited MAO-A with IC₅₀ values of 1.57 and 4.19 µM and had the highest selectivity indices (SIs) for MAO-B (120.8 and 107.4, respectively). T3 and T6 were found to be reversible and competitive inhibitors of MAO-B with K_i values of 0.014 and 0.0071, respectively. Moreover, T6 was less toxic to healthy fibroblast cells (L929) than T3. Molecular docking simulations with MAO binding sites returned higher docking scores for T6 and T3 with MAO-B than with MAO-A. These results suggest that T3 and T6 are selective, reversible, and competitive inhibitors of MAO-B and should be considered lead candidates for the treatment of neurodegenerative disorders like Alzheimer’s disease.     

Quantum chemical calculation for the inhibitory effect of compounds

The effects of the molecular structure on the corrosion inhibition efficiency are investigated by nine methods of calculations. The selected thio compounds were previously identified as corrosion inhibitors for mild steel in the 1.0 M HCl solution. The electronic properties such as highest occupied molecular orbital (EHOMO) energy, lowest unoccupied molecular orbital (ELUMO) energy, dipole moment (μ), and Fukui indices are calculated and discussed. Results show that the corrosion inhibition efficiency increase with the increase in both EHOMO and μ values, respectively, and decrease in ELUMO. QSAR approach is utilized in this study; a good relationship is found between the experimental corrosion inhibition efficiency (IE_exp, %) and the theoretical corrosion inhibition efficiency (IE_theor, %). The calculated inhibition efficiency is found closer to the experimental inhibition efficiency with a coefficient of correlation (R ²) of 0.875.     

Laser Writing of Block-Copolymer Images into Mesopores Using SBDC-Initiated Visible-Light-Induced Polymerization

For miniaturization, as well as for improving artificial nanopore performance, precise local polymer functionalization and the combination of different functionalities are required. Imagining data driven nanopore design automated nanopore functionalization would be beneficial. Using direct laser writing as one option of automated nanopore polymer functionalization visible light induced polymerizations are beneficial. Here, we demonstrate the functionalization of mesoporous silicafilms with two different polymers using automated laser writing. For this we developed a visible light (400–700 nm and 405 nm) N,N(diethylamino)dithiocarbamoylbenzyl(trimethoxy)silane (SBDC) inifierter initiated polymerization. While transferring this visible light induced polymerization using SBDC to a commercially available microscope, direct, automated laser writing, as well as polymer re-initiation was demonstrated. Thereby, polymer spots of 37 and 40 μm in diameter were achieved using 1–5 seconds for each irradiated spot.