Calix[4]arene-based Mannich and Schiff bases as versatile receptors for dichromate anion extraction: synthesis and comparative studies

A series of novel calix[4]arene-based Mannich (5 and 6) and Schiff base (9–11) receptors have been synthesized and characterized by various analytical techniques. Competitive two-phase extraction experiments of these novel calix[4]arene amine- and imine-containing derivatives revealed a strong affinity for dichromate anions $\left({\text{Cr}}_2{\text{O}}_7^{2?}/{\text{HCr}}_2{\text{O}}_7^{?}\right)$. The protonated alkylinium form of 5, 6 and 9–11 proved to be effective extractants for transferring the dichromate anions from an aqueous into an organic phase. Moreover, the extraction of dichromate anions by 5 and 9 in the presence of competitive anions such as F^?, Cl^?, Br^?, ${\text{NO}}_3^{?}$, ${\text{NO}}_2^{?}$, ${\text{PO}}_4^{3?}$ and ${\text{SO}}_4^{2?}$ showed that 5 and 9 could be selective anion receptors for dichromate anions in the presence of those anions.     

Numerical solutions of the Kawahara type equations using radial basis functions

This study is carried out to investigate the numerical solutions of the Kawahara, KdV‐Kawahara, and the modified Kawahara equations by using the meshless method based on collocation with radial basis functions. Results of the meshless method with different radial basis functions are presented for the travelling wave solution of the Kawahara type equations. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 28: 542–553, 2012     

Synthesis and characterization of new silicon-centred tin-dendrimers Si[CH2CH2SnR3]4. Single-crystal X-ray structure of the tetrahydrofuran adduct of tetrakis[2-(tribromostannyl)ethyl]silane

A series of novel first-generation silicon-centred tin dendrimers Si(CH₂CH₂SnR₃)₄ [R = CH₃ (3), ⁱBu (4), CCCH₃ (5), C₆H₄CH₃-4 (6), C₆H₄OCH₃-4 (7), (CH₂)₄OCH₂CH₂OCH₃ (8), CH₂SiMe₃ (9)] was prepared by the reaction of Si(CH₂CH₂SnBr₃)₄ (2) with the appropriate Grignard reagent or LiCH₂SiMe₃ in tetrahydrofuran. The new compounds were characterized by multinuclear NMR studies (¹H, ¹³C, ¹¹⁹Sn), mass spectrometry (MALDI-TOF, EI) and elemental analyses. The molecular structure of Si[CH₂CH₂SnBr₃(THF)₂]₂[CH₂-CH₂SnBr₃(THF)]₂ (2a) was determined by single-crystal X-ray diffraction.     

Electrorheological properties of PMMA-b-PSt copolymer suspensions

In this study, a block copolymer of methyl methacrylate (MMA) and styrene (St) synthesized by combined ultrasonic irradiation and reverse atom transfer radical polymerization (RATRP) processes was used. PMMA-b-PSt was partially hydrolyzed and converted to a lithium salt, PMMA-b-PSt-Li, before the electrorheological (ER) measurements carried out. Average particle diameter of PMMA-b-PSt-Li polymeric salt was determined by dynamic light scattering (DLS) as 22 mum. Suspensions of PMMA-b-PSt-Li polymeric salts were prepared in silicone oil. ER properties of PMMA-b-PSt-Li/silicone oil suspensions were studied as a function of electric field strength, dispersed phase concentration, shear rate, shear stress, temperature, frequency, and polar promoter. Further dielectric properties of PMMA-b-PSt-Li ionomer were also investigated.     

Synthesis,Crystal Structure,Spectroscopic and Electronic Properties of (E)-Trans-2-(2-(Biphenyl-4-ylmethylene)Hydrazinyl)-4-(3-Methyl-3-Phenylcyclobutyl)Thiazole

Abstract  

A new compound of (C₂₇H₂₅N₃S) has been synthesized and characterized by ¹H NMR, ¹³C NMR, IR, UV-Visible spectroscopy, and single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2₁/c and crystals of (I) were found approximately 0.5:0.5 ratio to be twinned. The crystal structure is stabilized by N–H···N inter molecular hydrogen bonding. In addition to the molecular geometry and dimeric structure from X-ray experiment, the optimized molecular geometry for monomer and dimer, vibrational frequencies, atomic charges distribution, and total energies of the title compound in the ground state have been calculated using ab initio method. Density Functional Theory (B3LYP) and Hartree-Fock (HF) methods with basis sets 6-31G(d, p) and 3-21G were used in the calculations. Calculated frequencies are in good agreement with the corresponding experimental data. UV-Vis absorption spectra of the compound have been ascribed to their corresponding molecular structure and electrons orbital transitions.     

Effect of ultrasound treatment on steady and dynamic shear properties of glucomannan based salep dispersions: optimization of amplitude level, sonication time and temperature using response surface methodology

The present study investigated effect of different amplitude levels (40, 70 and 100%), sonication temperatures (40, 50 and 60 °C) and exposure times (3, 7 and 11 min) on steady shear properties; apparent viscosity (η), shear stress (σ), consistency coefficient (K), flow behavior index (n) and dynamic shear properties; storage modulus (G′), loss modulus (G″), complex viscosity (η^∗), complex modulus (G^∗) and loss tangent (tan δ) values of glucomannan based salep solution (SS) and salep drink (SD) samples. In addition, the steady and dynamic shear properties were optimized using ridge analysis in terms of amplitude level, sonication temperature and exposure times levels. Increasing amplitude level and sonication time decreased considerably the η, σ, K, G′, G″ and η^∗ values of salep dispersions (SS and SD samples). However, sonication temperature did not have a remarkable effect on these properties.     

A DFT/TD-DFT study on the possible replacement of Ru(II) with Fe(II) in phthalocyanine-based dye-sensitized solar cells

Structural Chemistry - Density functional theory and time-dependent density functional theory (DFT/TD-DFT) methods have been used to study the photo-voltaic and photophysicochemical properties of...     

Multiscale Higuchi’s fractal dimension method

Nonlinear Dynamics - We investigate the closed-loop control of a circular cylinder showing lock-in phenomena due to vortex-induced vibrations (VIV). The control action was implemented by a...     

Weighted approximation by modified Picard operators

Positivity - Herein, the aim is to further investigate the properties of the generalized Picard operators introduced in Agratini et al. (Positivity 3(21):1189–1199, 2017). The motivation is...     

Electrical and optical properties of Co doped TlGaS2 crystals

In this study, Co doped TlGaS₂ single crystals which belongs to the class of A^IIIB^IIIX₂^VI have been investigated by means of XRD, temperature dependent dark and illuminated conductivity, Space Charge Limited Currents and absorption measurements. The room temperature conductivity and trap concentration values were about 10^‐8 (Ω‐cm)^‐1 and 7.5 × 10¹³ cm^‐3, respectively. From the temperature dependent conductivity measurements, two activation energies namely 271 and 12 meV have been determined in the high and low temperature regions, respectively. The trap level at 271 meV that was determined by the dark temperature dependent conductivity measurement has also been verified by Space Charge Limited Currents analysis. The absorption measurements have showed that the layered compound had indirect and direct band gaps and the values were determined to be 2.49 and 2.56 eV, respectively. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)