Molecular dynamic simulation of polymer and polymer-oxide nanoclusters

Small systems composed of 10 molecules of poly-p-xylylene or a TiO₂ cluster (rutile) surrounded by 10 molecules of poly-p-xylylene are modeled via the method of molecular dynamics. The thermodynamic characteristics, structure, and mobility of poly-p-xylylene chains in the model systems are studied in a wide temperature interval (195–995 K) and compared with the corresponding characteristics of a volume phase and an individual polymer chain. With increasing temperature, the mobility of monomer units increases; this process leads to disordering. At high temperatures, there is an evident tendency for loosening and further disintegration of an aggregate into individual chains, which adopt a Gaussian coil shape. These transitions are similar to the transitions of the folded individual molecule of poly-p-xylylene. Introduction of a TiO₂ nanoparticle into poly-p-xylylene has a strong effect on the characteristics of the system with short polymer chains, where the adhesion of poly-p-xylylene molecules on the TiO₂ surface is accompanied by disordering in the peripheral region.     

Compositions and structures of nanoparticles of pentagonal axial symmetry <Emphasis Type="Italic">D</Emphasis><Subscript>5<Emphasis Type="Italic">d</Emphasis></Subscript>: Nanotubes

The method of determination of the structure and the number of atoms in the shells of nanoparticles as a function of the arrangement of atoms at the symmetry elements of a symmetry group has been developed. The formulas for the calculation of the number of particles with symmetry group D _5d are reported. The number of particles in these shells is determined by three structurally invariant numbers and the “quantum number” of the group order n. The classification of all possible nanostructures with symmetry group D _5d is given: C _θ+10z , z = 0, 1, 2, …, where the basic shells are C _θ = C ₂, C ₁₀, C ₁₂. The sum rule has been obtained for the coordination numbers of shell sites located at symmetry axes. Pentagonal axial nanoparticles are shown to be the initial shells for obtaining (5,5) and (10,10) armchair nanotubes or (5,0) and (10,0) zigzag nanotubes. The general formula of these nanotubes closed with icosahedral and dodecahedral caps is N _20+10p , N _60+10p (p = 1, 2, …). The graphical constructions of all classes of nanoparticles and nanotubes of the pentagonal axial type are reported.     

Mechanochemical synthesis of colloidal silver bromide particles in the NaBr–AgNO<Subscript>3</Subscript>–NaNO<Subscript>3</Subscript> system

X-ray diffraction and thermal analyses, electron microscopy, and dynamic light scattering have been employed to study silver bromide nanoparticles obtained by the mechanochemical exchange reaction NaBr + AgNO₃ + zNaNO₃ = (z + 1)NaNO₃ + AgBr in sodium nitrate matrix (diluent and side reaction product) at z = z₁ = 8.06 and z = z₂ = 4.31. AgBr nanoparticles have been obtained in the free form by dissolving the matrix in water, and their activity in the photodegradation of methylene blue dye has been studied.     

Compositions and structures of nanoparticles of trigonal symmetry <Emphasis Type="Italic">D</Emphasis><Subscript>3<Emphasis Type="Italic">d</Emphasis></Subscript>: Nanotubes

A method has been developed for the determination of the structure and number of atoms in the shells of nanoparticles as a function of the arrangement of atoms at the symmetry elements of a symmetry group. The formulas for calculation of the number of particles of symmetry D _3d have been reported. It has been shown that the number of atoms in trigonal shells is determined by three structurally invariant numbers and the quantum number of the group order n. All possible nanostructures of symmetry D _3d have been classified: C_{θ + 6z} , z = 0, 1, 2, ..., where the basic shells are C_θ = C₆, C₈, and C₁₄. A sum rule has been obtained for the coordination numbers of the shell sites located on symmetry axes. Trigonal nanoparticles are parent ones for obtaining (3,0), (6,0), and (9,0) nanotubes of trigonal type. The general formulas of these nanotubes with icosahedral, dodecahedral, and cubic caps are N_{8 + 12p} , N_{20 + 24p} , and N_{60 + 36p} (p = 1, 2, ...), respectively. The graphical constructions of all classes of trigonal nanoparticles and nanotubes are reported.     

Biosynthesis of Gold Nanoparticles by Flavonoids from <Emphasis Type="Italic">Lilium casa blanca</Emphasis>

Biosynthesis of gold nanoparticles (GNPs) by flavonoids from Lilium casa blanca has been developed. Several parameters such as pH, reaction temperature, reaction time and concentration of flavonoids were explored to control the formation of the GNPs. The synthesized GNPs were characterized by UV–Vis spectroscopy, transmission electron microscopy and X-ray diffraction. Stability and catalytic activity of the synthesized GNPs were also discussed. The results showed that the synthesized GNPs were in spherical, about 2.6 nm, with a face centered cubic structure. Synthesized GNPs showed good catalytic activity in the reduction of p-nitrophenol (p-NP) to p-aminphenol (p-AP). This method for synthesis of GNPs is simple, economic, nontoxic and efficient.     

Modification of silica nanoparticles with stereisomers of <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylthiacalix[4]arene containing four 2-oxo-2-{[3-(triethoxysilyl)prop-1-yl]amino}ethoxy substituents at the lower rim

Three stereoisomers (cone, partial cone, and 1,3-alternate) of p-tert-butylthiacalix[4]arene bearing four anchor propyltriethoxysilane substituents at the lower rim were synthesized for the first time. Surface modification of silica nanoparticles (d = 12 nm) with the synthesized macrocycles gave novel hybride thiacalix [4]arene?SiO₂ particles. The obtained nanostructured adsorbents were found to efficiently extract nitroaromatic compounds from aqueous solutions. The partial cone and 1,3-alternate thiacalix[4]arene–SiO₂ hybrid particles showed affinity to nitrophenols.     

Chemoselective acylation of monosubstituted thiacalix[4]arene with di-<Emphasis Type="Italic">tert</Emphasis>-butyl dicarbonate

Mono-, di-, and tetrasubstituted derivatives of p-tert-butylthiacalix[4]arene containing tert-butylcarbamate, tert-butylcarbonate, and tert-butyl fragments have been prepared for the first time. Depending on the reaction conditions (reagents ratio, temperature, and the presence of a base), the interaction of the monoamine derivative of p-tert-butylthiacalix[4]arene with di-tert-butyl dicarbonate can lead to the formation of mono-, di-, and tetrasubstituted products.     

Influence of the structure of oxirane-containing compounds on curing of poly-<Emphasis Type="Italic">N</Emphasis>-methyl-5-vinyltetrazole

Comparative analysis of the curing performance of epoxy-containing cross-linking agents of different structure in vulcanization of a promising binder for energetic systems, poly-N-methyl-5-vinyltetrazole prepared by the modification procedure and containing residual N–H-unsubstituted tetrazole fragments, was made. Cross-linking of polymer chains of the binder is a result of alkylation of the residual N–H-unsubstituted tetrazole rings in poly-N-methyl-5-vinyltetrazole macromolecules with oxirane rings of the second reactant. Curing of poly-N-methyl-5-vinyltetrazole in the presence of macromolecular curing agents, carbon-chain polymers containing oxirane rings in pendant chains, at temperatures lower than 100°С occurs in a considerably narrower time interval compared to curing with low-molecular-mass epoxy resin.     

Investigation of cationic soapless P(St-<Emphasis Type="Italic">co</Emphasis>-DMAEMA) latex and its electrostatic adsorption of laponite

Cationic poly(styrene-co-N,N-dimethylaminoethyl methacrylate) (P(St-co-DMAEMA)) latexes were prepared in the absence of surfactant by using 2,2’ -azobis (2-methylpropionamidine) dihydrochloride (AIBA) as the initiator. The effects of the AIBA concentration, HCl/DMAEMA molar ratio and DMAEMA amount on the emulsion polymerization and the latex properties were investigated. The particle morphology and size, the zeta potential and the amino distribution of the P(St-co-DMAEMA) latexes were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS) and conductometric titration, respectively. Results showed that the emulsion polymerization performed smoothly with high monomer conversion and narrow particle size distribution under the optimized conditions with AIBA concentration of 1 wt%, HCl/DMAEMA molar ratio of 1.2 and DMAEMA content of 5 wt%. The diameter of the dried latex particles decreased and the density of amino groups on the particle surfaces increased with increasing the DMAEMA content. The zeta potential of the P(St-co-DMAEMA) latexes was pH-dependent and the zero point was around at pH 7.2. A facile method was developed to fabricate P(St-co-DMAEMA)/laponite hybrid nanoparticles via electrostatic adsorption, in which the loading capacity of laponite platelets reached 17.7 wt%, and the resultant hybrid nanoparticles showed good thermal stability.     

Reductive acylamination of pyridine <Emphasis Type="Italic">N</Emphasis>-oxide with ethylenediamine and phenylenediamines

Reactions of pyridine N-oxide with ethylenediamine and o- and p-phenylenediamines in the presence of p-toluenesulfonyl chloride in alkaline medium lead to the formation of the corresponding N,N′-bis-(p-tolylsulfonyl)-N,N′-bis(pyridin-2-yl)diamines as a result of reductive acylamination.     

Synthesis of isoxazole derivatives of 4,5-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrazole

Cyclocondensation of pent-1-en-4-yn-3-one with phenylhydrazine and p-tolylhydrazine occurs at the positions 1, 3. Proceeding from the 1-aryl-3-ethynyl-4,5-dihydro-1H-pyrazoles formed in the reaction in yields up to 95% we prepared potentially biologically active isoxazole derivatives of pyrazoline. The structure of 5-[1-(4-methylphenyl)-4,5-dihydro-1H-pyrazol-3-yl]-3-phenyl-1,2-oxazole was studied by X-ray diffraction analysis.     

X-ray diffraction and thermodynamic characteristics for tellurite of the composition Li<Subscript>2</Subscript>CeTeO<Subscript>5</Subscript>

Tellurite of the composition Li₂CeTeO₅ is synthesized by solid-phase method from cerium(IV) and tellurium(IV) oxides and lithium carbonate. The type of syngony, the unit cell parameters, and the compound’s X-ray and pycnometry densities are determined via X-ray diffraction analysis. The isobaric heat capacity of lithium–cerium tellurite is studied by means of dynamic calorimetry in the temperature range of 298.15–673 K; the results serve as the basis for deriving C _p ^° ~ f(T) dependency equations and determining the compound’s thermodynamic functions. λ-shaped anomalous effects, due probably to Type II phase transitions, are found on the C _p ^° ~ f(T) dependence.     

<Emphasis Type="Italic">Leucas aspera</Emphasis> Nanomedicine Shows Superior Toxicity and Cell Migration Retarded in Prostate Cancer Cells

Prostate cancer is one of the most common malignancies among men worldwide. The main aim of the present work was to clarify the advantages of a nanoformulation of ayurvedic herbal plants. Specifically, we assessed the improved anticancer activity of Leucas aspera nanoparticles compared with methanolic crude extract in PC3 prostate cancer cells and normal cells. L. aspera is a plant that is used in ayurveda due to the antirheumatic, antipyretic, anti-inflammatory, antibacterial, anticancer, and cytotoxic activities. Nanoparticles of L. aspera were prepared from plant methanolic extracts. Cytotoxic effect was studied in the normal and prostate cancer cells. Size and morphology of the formulated nanoparticles was assessed using dynamic light scattering and scanning electron microscopy. In vitro cytotoxicity of L. aspera nanoparticles for PC3 cells was concentration- and time-dependent. In vitro hemolysis assay, cellular uptake studies, cell aggregation studies, and cell migration assay established the anticancerous activity of L. aspera in prostate cancer.     

Synthesis and biological activity of hydrazones of <Emphasis Type="Italic">o</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-hydroxybenzoic acids. Spatial structure of 5-Bromo-2-hydroxybenzylidene-4-hydroxybenzohydrazide

A series of hydrazones based on hydrazides of o- and p-hydroxybenzoic acids have been prepared. N-(5-Bromo-2-hydroxybenzylidene)-4-hydroxybenzohydrazide has been studied by X-ray diffraction analysis; its molecule forms hydrogen bond with a solvating ethanol molecule. Biological activity of the synthesized hydrazones towards cathepsin Е and(or) elastase of human neutrophils has been determined.     

X-ray diffraction study of CsZn<Subscript>2</Subscript>Br<Subscript>5</Subscript>

CsZn₂Br₅ crystals are studied by X-ray diffraction. The compound crystallizes in the monoclinic system with the unit cell parameters a = 6.8880(12) Å, b = 10.4703(19) Å, c = 6.5197(9) Å, β = 108.25°, V = 446.55 ų, ρ_calcd = 4.960 g/cm³. Refractive indices are n _p = 1.640 and n _p = 1.754.     

Sulfonic acid-functionalized titanomagnetite nanoparticles as recyclable heterogeneous acid catalyst for one-pot solvent-free synthesis of 3,4-dihydropyrimidin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones/thiones

Sulfonic acid-functionalized titanomagnetite (Fe_3?x Ti _x O₄@SO₃H) nanoparticles were prepared by grafting sulfonic acid groups on Fe_3?x Ti _x O₄ nanoparticles. This new heterogeneous acid nanocatalyst demonstrated an efficient catalytic performance in the one-pot synthesis of dihydropyrimidin-2(1H)-one/thione derivatives under solvent-free conditions with high yields. The nanocatalyst could easily be separated from the reaction mixture simply by using an external magnet, recycled and reused for several times with no significant loss of catalytic activity. These nanoparticles were characterized by different physicochemical techniques, such as Fourier transform infrared, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetric and vibrating sample magnetometer (VSM) analyses.     

Synthesis and molecular structure of [2,3,4,5-tetrafluoro-6-(<Emphasis Type="Italic">p</Emphasis>-methoxyphenylamino)phenyl]diphenylphosphine

The reaction of (pentafluorophenyl)diphenylphosphine with C-ethoxycarbonyl-(p-methoxyphenyl) nitrile imine was used to synthesize [2,3,4,5-tetrafluoro-6-(p-methoxyphenylamino)phenyl]diphenylphosphine oxide whose reduction with trichlorosilane gave [2,3,4,5-tetrafluoro-6-(p-methoxyphenylamino)phenyl] diphenylphosphine, the first representative of tertiary ortho-arylamino-substituted arylphosphines. According to X-ray diffraction data, the principal steric characteristics of the phosphine are close to those known for triarylphosphines.     

Crystal structure and luminescence of a terbium complex with <Emphasis Type="Italic">p</Emphasis>-methyl benzoate and 1,10-phenanthroline

A terbium p-methyl benzoate complex with 1,10-phenanthroline, [Tb(p-MBA)₃(Phen)]₂ (p-MBA = p-methyl benzoate and Phen = 1,10-phenanthroline), has been prepared and structurally characterized by X-ray diffraction. It crystallizes in triclinic system, space group P \(\bar 1\) with a = 12.8064(12), b = 13.3589(12), c = 19.8277(19) Å, α = 91.668(2)°, β = 97.775(2)°, γ = 106.312(2)°, C₇₂H₅₈N₄O₁₂Tb₂, M _r = 1489.06, V = 3217.6(5) ų, Z = 2, ρ _c = 1.537 g/cm³, μ(MoK _α) = 2.246 mm^?1, F(000) = 1488, the final R = 0.0622 and wR = 0.0962 for 14128 independent reflections with R _int = 0.0843. It consists of two types of crystallographically independent dimeric molecules [Tb(p-MBA)₃(Phen)]₂ noted as [Tb-1] and [Tb-2]. In the dimeric molecule [Tb-1], each Tb(III) is eight-coordinated with one Phen molecule, two bridging carboxylate groups, and two bidentate chelating carboxylate groups, while in [Tb-2] each Tb(III) is eight-coordinated with one Phen molecule, four bridging carboxylate groups, and one bidentate chelating carboxylate group. The title complex shows intense green luminescence under UV light at room temperature.     

Theoretical and experimental study of molecular structure and vibrational spectra of <Emphasis Type="Italic">N</Emphasis>-(2-pyridylmethyl)-2-pyrazinecarboxamide

N-(2-Pyridylmethyl)-2-pyrazinecarboxamide was prepared and its crystal structure was investigated by X-ray analysis. The compound crystallizes in the triclinic space group \(P{\bar 1}\) with a = 4.262(3), b = 12.117(9), c = 20.840(18) Å, α = 91.802(6), β = 89.834(7), γ = 91.845(6)°, V = 1075.2(16) ų, Z = 4, and D = 1.323?Mg/m³. The structure was solved by direct method and refined to R = 0.0699 and wR ₂ = 0.1268 by full matrix anisotropic least-squares method. Using the Hartree-Fock and density functional method (B3LYP) with 6-31G(d) basis set, the molecular geometry and vibrational frequencies of the title compound has been investigated and compared with experimental ones from experimental studies. The optimized bond lengths obtained by RHF method and bond angles obtained by B3LYP method show better agreement with the experimental values. The vibrations computed of the title compound by the RHF and DFT methods are in good agreement with the observed IR spectra data.     

Influence of the Molecular Mass of Poly(<Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone) on Formation of Cu<Subscript>2</Subscript>O Nanoparticles During Reduction of Divalent Copper Ions with <Emphasis Type="Italic">tert</Emphasis>-Butylamine Borane in Polymer Solution

The process of reduction of divalent copper ions with tert-butylamine borane in dilute aqueous solutions of poly(N-vinylpyrrolidone) is investigated. The influence of polymer molecular mass on properties of the resultant Cu₂O sols is studied. It is shown that Cu₂O nanoparticles with an average diameter of 6–8 nm independent of polymer molecular mass and a relatively narrow size distribution of particles are formed in the systems under study. The contour length of macromolecules and the hydrodynamic diameter of a poly(N-vinylpyrrolidone) macromolecular coil are compared with the diameter of Cu₂O particles. Poly(N-vinylpyrrolidone) with M ≥ 1 × 10⁴ can be used to produce Cu₂O nanoparticles. Poly(N-vinylpyrrolidone) with M > 4 × 10⁴ should be used for the formation of long-living Cu₂O sols.