Design and Antioxidant Properties of Bifunctional 2H-Imidazole-Derived Phenolic Compounds—A New Family of Effective Inhibitors for Oxidative Stress-Associated Destructive Processes

The synthesis of inhibitors for oxidative stress-associated destructive processes based on 2H-imidazole-derived phenolic compounds affording the bifunctional 2H-imidazole-derived phenolic compounds in good-to-excellent yields was reported. In particular, a series of bifunctional organic molecules of the 5-aryl-2H-imidazole family of various architectures bearing both electron-donating and electron-withdrawing substituents in the aryl fragment along with the different arrangements of the hydroxy groups in the polyphenol moiety, namely derivatives of phloroglucinol, pyrogallol, hydroxyquinol, including previously unknown water-soluble molecules, were studied. The structural and antioxidant properties of these bifunctional 5-aryl-2H-imidazoles were comprehensively studied. The redox transformations of the synthesized compounds were carried out. The integrated approach based on single and mixed mechanisms of antioxidant action, namely the AOC, ARC, Folin, and DPPH assays, were applied to estimate antioxidant activities. The relationship “structure-antioxidant properties” was established for each of the antioxidant action mechanisms. The conjugation effect was shown to result in a decrease in the mobility of the hydrogen atom, thus complicating the process of electron transfer in nearly all cases. On the contrary, the conjugation in imidazolyl substituted phloroglucinols was found to enhance their activity through the hydrogen transfer mechanism. Imidazole-derived polyphenolic compounds bearing the most electron-withdrawing functionality, namely the nitro group, were established to possess the higher values for both antioxidant and antiradical capacities. It was demonstrated that in the case of phloroglucinol derivatives, the conjugation effect resulted in a significant increase in the antiradical capacity (ARC) for a whole family of the considered 2H-imidazole-derived phenolic compounds in comparison with the corresponding unsubstituted phenols. Particularly, conjugation of the polyphenolic subunit with 2,2-dimethyl-5-(4-nitrophenyl)-2H-imidazol-4-yl fragment was shown to increase ARC from 2.26 to 5.16 (10⁴ mol-eq/L). This means that the considered family of compounds is capable of exhibiting an antioxidant activity via transferring a hydrogen atom, exceeding the activity of known natural polyphenolic compounds.     

One-Step Synthesis of Magnetic Nanocomposite with Embedded Biologically Active Substance

Magnetic nanocomposites based on hydroxyapatite were prepared by a one-step process using the hydrothermal coprecipitation method to sinter iron oxides (Fe₃O₄ and γ-Fe₂O₃). The possibility of expanding the proposed technique for the synthesis of magnetic composite with embedded biologically active substance (BAS) of the 2-arylaminopyrimidine group was shown. The composition, morphology, structural features, and magnetic characteristics of the nanocomposites synthesized with and without BAS were studied. The introduction of BAS into the composite synthesis resulted in minor changes in the structural and physical properties. The specificity of the chemical bonds between BAS and the hydroxyapatite-magnetite core was revealed. The kinetics of the BAS release in a solution simulating the stomach environment was studied. The cytotoxicity of (HAP)FexOy and (HAP)FexOy + BAS composites was studied in vitro using the primary culture of human liver carcinoma cells HepG2. The synthesized magnetic composites with BAS have a high potential for use in the biomedical field, for example, as carriers for magnetically controlled drug delivery and materials for bone tissue engineering.     

Quantum Monte Carlo assessment of density functionals for π-electron molecules: ethylene and bifuran

ABSTRACT

We perform all-electron, pure-sampling quantum Monte Carlo (QMC) calculations on ethylene and bifuran molecules. The orbitals used for importance sampling with a single Slater determinant are generated from Hartree-Fock and density functional theory (DFT). Their fixed-node energy provides an upper bound to the exact energy. The best performing density functionals for ethylene are BP86 and M06, which account for 99% of the electron correlation energy. Sampling from the π-electron distribution with these orbitals yields a quadrupole moment comparable to coupled cluster CCSD(T) calculations. However, these, and all other density functionals, fail to agree with CCSD(T) while sampling from electron density in the plane of the molecule. For bifuran, as well as ethylene, a correlation is seen between the fixed-node energy and deviance of the QMC quadrupole moment estimates from those calculated by DFT. This suggests that proximity of DFT and QMC densities correlates with the quality of the exchange nodes of the DFT wave function for both systems.     

AC-driven bilayer graphene: quasienergy spectrum of electrons and generation of soliton-like electromagnetic pulse

Quasienergy spectrum of electrons in biased bigraphene subjected to the linear polarized high-frequency electromagnetic radiation has been derived. Quasienergy bands of ac-driven bigraphene have been investigated. Dynamical appearing of the saddle points in band structure of biased bigraphene and energy gap modification have been predicted. Electromagnetic field equation has been written using obtained quasienergy spectrum. The solution corresponding to the soliton-like electromagnetic wave has been obtained. The conditions of soliton-like wave generation in ac-driven bigraphene have been discussed.     

Blow‐up phenomena in the model of a space charge stratification in semiconductors: analytical and numerical analysis

The initial‐boundary value problems for a Sobolev equation with exponential nonlinearities, classical, and nonclassical boundary conditions are considered. For this model, which describes processes in crystalline semiconductors, the blow‐up phenomena are studied. The sufficient blow‐up conditions and the blow‐up time are analyzed by the method of the test functions. This analytical a priori information is used in the numerical experiments, which are able to determine the process of the solution's blow‐up more accurately. The model derivation and some questions of local solvability and uniqueness are also discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Electronic spectrum of the AlC(2) radical

An electronic transition of the AlC2 radical (C2v structure) has been observed using laser-induced fluorescence spectroscopy. The molecule was prepared in a supersonic expansion by ablation of an aluminum rod in the presence of acetylene gas. A spectrum was recorded in the 451-453 nm region and assigned to the C 2B2-X 2A1 system (T0 = 22,102.7 cm(-1)) based on a rotational analysis and agreement with calculated molecular parameters and excitation energies. Ab initio results obtained using couple cluster methods are in accord with previous theoretical work which concludes that ground-state AlC2 possesses a T-shaped C2v 2A1 geometry, with the linear 2Sigma+ AlCC isomer 0.70 eV higher in energy. A fit of the experimental spectrum yields rotational constants in the ground and electronically excited states that are in reasonable agreement with the calculated values: A' = 1.7093(107), B' = 0.4052(50), C' = 0.3228(49) cm(-1) for the X 2A1 state, and A' = 1.5621(137), B' = 0.4028(46), C' = 0.3201(54) cm(-1) for C 2B2. Variation in individual fluorescence lifetimes suggests that the emitting C 2B2 state undergoes rovibronic mixing with lower lying electronic states.     

Superposition operator on the space of sequences almost converging to zero

We study the superposition operator f on on the space ac ₀ of sequences almost converging to zero. Conditions are derived for which f has a representation of the form f x = a+bx +g x, for all x ∈ ac ₀ with a = f 0, b ∈ D(ac ₀), g a superposition operator from ℓ_∞ into I(ac ₀), D(ac ₀) = {z: zx ∈ ac ₀ for all x ∈ ac ₀}, and I(ac ₀) the maximal ideal in ac ₀. If f is generated by a function f of a real variable, then f is linear. We consider the conditions for which a bounded function f generates f acting on ac ₀ and the conditions for which there exists a sequence y ∈ ac ₀ such that y − f y ∈ ac ₀. In terms of f, criteria for the boundedness, continuity, and sequential σ(ac ₀ℓ₁)-continuity of f on ac ₀ are given. It is shown that the continuity of f is equivalent to the weak sequential continuity. Finally, properties of spaces D(ac ₀) and I(ac ₀) are studied, and in particular it is established that the inclusion I(ac ₀) ⊕ {λe: λ ∈ ℝ} ⊂ D(ac ₀) is proper, where e = (1, 1, …). By means of D(ac ₀), a number of Banach-Mazur limit properties are derived.     

Intramolecular Copper(I)‐Catalyzed Interrupted Click–Acylation Domino Reaction

Acyl substituted triazoles are valuable scaffolds, but the direct synthesis of these moieties from terminal alkynes by copper catalysis remains unexplored. We report a robust, general, and efficient method using a simple CuI/2,2′‐bipyridine catalytic system. This transformation involves a copper catalyzed azide‐alkyne cycloaddition (CuAAC) followed by an intramolecular acylation onto a carbamoyl chloride. The reaction proceeds under mild conditions, tolerates several functional groups, and is readily scalable. This method represents a novel strategy towards the synthesis of complex heterocycles by a CuAAC/acylation domino process.