Stereoselective aziridination of imines via ammonium ylides: A molecular electron density theory study

The highly trans-stereoselective reaction of ammonium salt ( AS 2 ) toward (E)-N-benzylidene-4-methylbenzenesulfonamide ( IM 4 ) in the presence of Na₂CO₃ leading to an aziridine derivative, trans -Az 6 , was theoretically studied using Molecular Electron Density Theory (MEDT) at the B3LYP/6-31G(d) computational level to probe energy transformation, selectivities, and molecular mechanism. The reaction starts by a nucleophilic substitution reaction between 1,4-diazabicyclo [2.2.2]octane ( DABCO ) and phenacyl bromide ( PB ) to form AS 2 which undergoes a proton abstraction by Na₂CO₃ to produce Ammonium Ylide ( AY 3) . Subsequently, nucleophilic addition of AY 3 to the double bond in IM 4 leads to form a betaine-like intermediate, namely, IN-Ta which named IN-Ta . Finally, trans -Az 6 is produced as a result of the nucleophilic attack of the negatively charged nitrogen atom on the carbon atom bearing DABCO in IN-Ta . Analysis of the relative Gibbs free energies shows that the ring closure step is the rate-determining step (RDS). By an investigation of the conceptual density functional theory, CDFT reactivity indices AY 3 and IM 4 are classified as a strong nucleophilic molecular system and as a strong electrophilic molecular system, respectively, which implies that the addition step of AY 3 to IM 4 has a high polar character. An analysis of the calculated electrophilic and nucleophilic Parr functions at the reactive sites of reagents clarifies the regioselectivity observed experimentally within the C₁–C₂ bond creation process.     

Hybrid conduction,convection and radiation heat transfer simulation in a channel with rectangular cylinder

Journal of Thermal Analysis and Calorimetry - The innovation of this study is to investigate the combination effect of thermal radiation and convection in the hybrid heat transfer between solid and...     

Effects of perforated anchors on heat transfer intensification of turbulence nanofluid flow in a pipe

Journal of Thermal Analysis and Calorimetry - In this paper, a study is conducted to determine the influences of perforated anchors on heat transfer intensification of turbulence nanofluid flow in...     

The global convergence of the BFGS method under a modified Yuan-Wei-Lu line search technique

Numerical Algorithms - This paper is focused on improving global convergence of the modified BFGS algorithm with Yuan-Wei-Lu line search formula. This improvement has been achieved by presenting a...     

Effect of gamma irradiation on antioxidant potential,isoflavone aglycone and phytochemical content of soybean (Glycine max L. Merrill) cultivar Williams

Journal of Radioanalytical and Nuclear Chemistry - In this study, we investigated the effects of irradiation on phytochemical content of soybean. Soybean seeds were irradiated at different doses of...     

CeO2/CuO@N-GQDs@NH2 nanocomposite as a high-performance catalyst for the synthesis of benzo[g]chromenes

A three-component reaction of aromatic aldehydes, malononitrile or ethyl cyanoacetate and 2-hydroxy-1,4-naphthaquinone has been achieved in the presence of an amino-functionalized CeO₂/CuO@ nitrogen graphene quantum dot nanocomposite as a highly effective heterogeneous catalyst to produce benzo[g]chromenes. The catalyst has been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) and vibrating sample magnetometry. This new catalyst has been demonstrated to be highly effective in the preparation of benzo[g]chromenes.     

Synthesis,characterization and theoretical and fluorescence emission microscopy studies of new Pd/Pt–cyclopropa[60]fullerene complexes: Application of Taguchi method for optimization of parameters in Suzuki–Miyaura reaction

The reactions of unsymmetric phosphorus ylides of the type [Ph₂P(CH₂)_nPPh₂?C(H)C(O)C₆H₄‐p‐CN] (n = 1 (Y¹); n = 2 (Y²)) with C₆₀ and M(dba)₂ (M = Pd or Pt; dba = dibenzylideneacetone) are reported. Based on the various coordination modes of these ylides in complexation, the following new Pd/Pt–cyclopropa[60]fullerene complexes were obtained: P,C‐coordinated [(η²‐C₆₀)Pd(κ²‐Y¹)] ( 1 ) and [(η²‐C₆₀)Pt(κ²‐Y¹)] ( 2 ) complexes and P‐coordinated [(η²‐C₆₀)Pd(Y²)₂] ( 3 ) and [(η²‐C₆₀)Pt(Y²)₂] ( 4 ) complexes. These compounds were characterized using Fourier transform infrared, UV–visible and NMR (¹H, ¹³C and ³¹P) spectroscopies and scanning electron microscopy. Furthermore, cytotoxicity studies showed that nanoparticles of these complexes can be used as non‐toxic labels for cellular imaging application. Also energy decomposition analysis results revealed that the percentage contribution of ΔE_elec in total interaction energy is considerably larger than that of ΔE_orb. Thus, in all complexes the (η²‐C₆₀)M? (Y¹) bond is considerably more electrostatic in nature than the (η²‐C₆₀)? M(Y¹) bond. Finally, by application of the Taguchi method for optimization of parameters in Suzuki–Miyaura reaction, the catalytic activity of Pd complexes 1 and 3 was investigated in the cross‐coupling reaction of various aryl chlorides with phenylboronic acid. According to analysis of variance results, solvent has the highest F value and it has high contribution percentage (36.75%) to the yield of Suzuki–Miyaura reaction.     

Competitive Potentiometric Study of the Thermodynamics of Complexation of Some Transition and Heavy Metal Ions with Dibenzopyridino-18-crown-6 in Methanol using Ag+ Ion as a Probe

The complexation of dibenzopyridino-18-crown-6 with some transition and heavy metal ions in methanol solution at various temperatures was studied by a competitive potentiometric method using a Ag⁺/Agelectrode system. The stoichiometry and stability of the resulting complexes were computed by the MINIQUAD program. The stability of the resulting complexes varied in the order Ag⁺ > Pb²⁺ > Tl⁺ > Cu²⁺ > Cd²⁺ > Zn²⁺. The enthalpy and entropy of the resulting 1:1 complexeswere evaluated from the temperature dependence of the stability constants.The complexes of all cations were enthalpy-stabilized but entropy-destabilized,except for Ag⁺ and Pb²⁺ ions,which were also entropy-stabilized.     

Immobilization of glucose oxidase on ZnO nanorods decorated electrolyte-gated field effect transistor for glucose detection

In this paper, we report on growth of ZnO nanorods on the surface of gold interdigital electrodes and its implementation as a conductive n-type channel for the fabrication of a liquid-gated field effect transistor. Glucose oxidase was immobilized on the surface of the ZnO nanorods and the fabricated device was used as a four-electrode glucose biosensor. The resistance of the conductive channel was affected by addition of glucose. The applied bias voltage to the gate in the fabricated device affects the channel resistance in the same manner as the increase of enzymatic products during the glucose oxidation. Large effective area, good conductivity, and biocompatibility properties of ZnO nanorods are the key features in this highly sensitive and stable biosensor. Our measurements showed that the threshold voltage of transistor was about 0.75 V. The current increased in the presence of the glucose and exhibited a dynamic linear range with the logarithm of glucose concentration in the range between 0.01 and 5 mM. The detection limit was about 3.8 μM.     

Structural Transformation of Surface-Confined Porphyrin Networks by Addition of Co Atoms

The self-assembly of a nickel-porphyrin derivative (Ni-DPPyP) containing two pyridyl coordinating sites and two pentyl chains at trans meso positions was studied with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) on Au(111). Deposition of Ni-DPPyP onto Au(111) gave rise to a close-packed network for coverages smaller or equal to one monolayer as revealed by STM and LEED. The molecular arrangement of this two-dimensional network is stabilized via hydrogen bonds formed between the pyridyl's nitrogen and hydrogen atoms from the pyrrole groups of neighboring molecules. Subsequent deposition of cobalt atoms onto the close-packed network and post-deposition annealing at 423 K led to the formation of a Co-coordinated hexagonal porous network. As confirmed by XPS measurements, the porous network is stabilized by metal-ligand interactions between one cobalt atom and three pyridyl ligands, each pyridyl ligand coming from a different Ni-DPPyP molecule.