Conductance Study of Binding of Some Rb+ and Cs+ Ions by Macrocyclic Polyethers in Acetonitrile Solution

A conductance study of the interaction between Rb+ and Cs+ ions and18-crown-6 (18C6), dicyclohexyl-18-crown-6 (DC18C6), dibenzo-18-crown-6 (DB18C6),dibenzo-24-crown-8 (DB24C8), and dibenzo-30-crown-10 (DB30C10) inacetonitrile solution has been carried out at various temperatures. The formationconstants of the resulting 1:1 complexes were determined from the molarconductance-mole ratio data and found to vary in the orderDC18C6 > 18C6 > DB30C10 > DB18C6 DB24C8for Rb+ ion andDC18C6 > 18C6 > DB30C10 DB24C8 > DB18C6for Cs+ ion. The enthalpy and entropy of complexation were determined fromthe temperature dependence of the formation constants. The complexes with the18-crowns are both enthalpy and entropy stabilized while, in the case of largecrown ethers, the corresponding complexes are enthalpy stabilized but entropydestabilized.     

Green synthesis of Fe3O4/ZnO magnetic core-shell nanoparticles by Petasites hybridus rhizome water extract and their application for the synthesis of pyran derivatives: Investigation of antioxidant and antimicrobial activity

In this research, Fe₃O₄/ZnO magnetic core-shell nanoparticles (Fe₃O₄/ZnO MCNPs) were synthesized through a green method using Petasites hybridus rhizome water extract as a reducing and stabilizing agent. The morphology and size of the Fe₃O₄/ZnO MCNPs was identified by X-ray diffraction, scanning electron microscopy, and Energy-dispersive X-ray spectroscopy (EDX) analysis. The catalytic activity of the Fe₃O₄/ZnO MCNPs was evaluated in the efficient and green preparation of pyran derivatives in excellent yield using three-component reactions of dimedone, aldehydes, and malononitrile in ethanol at room temperature. The ability of some synthesized compounds to scavenge the 2,2-diphenyl-1-picrylhydrazyl radical was measured and the results proved this observation. Moreover, the antimicrobial activity of some synthesized compounds was proved by employing the disk diffusion test on Gram-positive and Gram-negative bacteria. The results for the disk diffusion test showed that compounds ( 4c, 4d, 4f and 4g ) prevented bacterial growth.     

Invariant Pseudolinearity with Applications

In this paper, we introduce the notion of invariant pseudolinearity for nondifferentiable and nonconvex functions by means of Dini directional derivatives. We present some characterizations of invariant pseudolinear functions. Some characterizations of the solution set of a nonconvex and nondifferentiable, but invariant, pseudolinear program are obtained. The results of this paper extend various results for pseudolinear functions, pseudoinvex functions, and η-pseudolinear functions, and also for pseudoinvex programs, pseudolinear programs, and η-pseudolinear programs.     

Al2O3/MeSO3H: A Novel and Recyclable Catalyst for One-Pot Synthesis of 3,4-Dihydropyrimidinones or Their Sulfur Derivatives in Biginelli Condensation

Al₂O₃/CH₃SO₃H (AMA) is an efficient catalyst for the three-component condensation reaction of aldehyde, 1,3-dicarbonyl compound, and urea or thiourea to afford the corresponding 3,4-dihydropyrimidin-2-(1H)-ones in high isolated yield via this procedure, which works very effectively regardless of the electronic nature of the substituent on the ring, although electron-donating groups precipitate the rate of reaction. The catalyst is recyclable and stable at room temperature, and the reaction protocol is simple, is cost-effective, and gives good isolated yield with high purity.     

Developing Eco-Friendly and Cost-Effective Porous Adsorbent for Carbon Dioxide Capture

To address the issue of global warming and climate change issues, recent research efforts have highlighted opportunities for capturing and electrochemically converting carbon dioxide (CO₂). Despite metal doped polymers receiving widespread attention in this respect, the structures hitherto reported lack in ease of synthesis with scale up feasibility. In this study, a series of mesoporous metal-doped polymers (MRFs) with tunable metal functionality and hierarchical porosity were successfully synthesized using a one-step copolymerization of resorcinol and formaldehyde with Polyethyleneimine (PEI) under solvothermal conditions. The effect of PEI and metal doping concentrations were observed on physical properties and adsorption results. The results confirmed the role of PEI on the mesoporosity of the polymer networks and high surface area in addition to enhanced CO₂ capture capacity. The resulting Cobalt doped material shows excellent thermal stability and promising CO₂ capture performance, with equilibrium adsorption of 2.3 mmol CO₂/g at 0 °C and 1 bar for at a surface area 675.62 m²/g. This mesoporous polymer, with its ease of synthesis is a promising candidate for promising for CO₂ capture and possible subsequent electrochemical conversion.     

A generalization of the Erdös-Ko-Rado theorem

In this note, we investigate some properties of local Kneser graphs defined in [János Körner, Concetta Pilotto, Gábor Simonyi, Local chromatic number and sperner capacity, J. Combin. Theory Ser. B 95 (1) (2005) 101-117]. In this regard, as a generalization of the Erdös-Ko-Rado theorem, we characterize the maximum independent sets of local Kneser graphs. Next, we provide an upper bound for their chromatic number.     

Fragmentation energetics of the phenol(+)···Ar(3) cation cluster

The various dissociation thresholds of phenol(+)···Ar(3) complexes for the consecutive loss of all three Ar ligands were measured in a molecular beam using resonant photoionization efficiency and mass analyzed threshold ionization spectroscopy via excitation of the first excited singlet state (S(1)). The adiabatic ionization energy is derived as 68077 ± 15 cm(-1). The analysis of the dissociation thresholds demonstrate that all three Ar ligands in the neutral phenol···Ar(3) tetramer are attached to the aromatic ring via π-bonding, denoted phenol···Ar(3)(3π). The value of the dissociation threshold for the loss of one Ar ligand from phenol(+)···Ar(3)(3π), ～190 cm(-1), is significantly lower than the binding energy measured for the π-bonded Ar ligand in the phenol(+)···Ar(π) dimer, D(0) = 535 ± 3 cm(-1). This difference is rationalized by an ionization-induced π → H isomerization process occurring prior to dissociation, that is, one Ar atom in phenol(+)···Ar(3)(3π) moves to the OH binding site, leading to a structure with one H-bonded and 2 π-bonded ligands, denoted phenol(+)···Ar(3)(H/2π). The dissociation thresholds for the loss of two and three Ar atoms are also reported as 860 and 1730 cm(-1). From these values, the binding energy of the H-bound Ar atom can be estimated as 870 cm(-1).