Graphene oxide promoted synthesis of <Emphasis Type="Italic">p</Emphasis>-phenylenediamine antioxidants

Three p-phenylenediamine antioxidants (p-phenylenediamine-N,N,N′,N′-tetrapropionic acid tetramethyl ester, p-phenylenediamine-N,N,N′-tripropionic acid trimethyl ester, and p-phenylenediamine-N, N′-dipropionic acid dimethyl ester) were successfully synthesized via atom-economic aza-Michael addition of pphenylenediamine to methyl acrylate p-romoted by graphene oxide in water. The synthesized compounds were characterized by NMR, ESI-MS spectra, and elemental analyses. The effects of the solvent and graphene oxide on the reaction were investigated.     

Studies of chemical stage of synthesis of electroactive composite based on poly-<Emphasis Type="Italic">o</Emphasis>-phenylenediamine and graphene oxide

Formation of an electroactive composite based on graphene oxide and poly-o-phenylenediamine (PPD) was studied. Electron absorption spectra were used to confirm formation of a strong chemical bond at a prolonged contact of unreduced graphene oxide on a conducting support (glassy carbon, SnO₂) and o-phenylenediamine monomer solution. Here, graphene oxide is partially reduced and oxidation and partial polymerization of o-phenylenediamine starts. It is shown that electrochemical oxidation of the obtained composite under the conditions of cyclic voltammetry results in the further polymerization of o-phenylenediamine bound to graphene oxide; here, reduction of graphene oxide continues, and at much lower cathodic potentials than in the absence of o-phenylenediamine. Morphology of the obtained composite was studied using the AFM technique. PPD embedded into the composite structure does not allow nanosheets of reduced graphene oxide (RGO) to corrugate and imparts the morphology of the composite the shape of globules with a clearly pronounced structure. As a result, the RGO–PPD composite was obtained that demonstrated pronounced electroactivity in a wider range of potentials than in the case of nonmodified PPD.     

The effect of particle shape on the structure and rheological properties of carbon-based particle suspensions

The structure and rheological properties of carbon-based particle suspensions, i.e., carbon black(CB), multi-wall carbon nanotube(MWNT), graphene and hollow carbon sphere(HCS) suspended in polydimethylsiloxane(PDMS), are investigated. In order to study the effect of particle shape on the structure and rheological properties of suspensions, the content of surface oxygen-containing functional groups of carbon-based particles is controlled to be similar. Original spherical-like CB(fractal filler), rod-like MWNT and sheet-like graphene form large agglomerates in PDMS, while spherical HCS particles disperse relatively well in PDMS. The dispersion state of carbon-based particles affects the critical concentration of forming a rheological percolation network. Under weak shear, negative normal stress differences(ΔN) are observed in CB, MWNT and graphene suspensions, while ΔN is nearly zero for HCS suspensions. It is concluded that the vorticity alignment of CB, MWNT and graphene agglomerates under shear results in the negative ΔN. However, no obvious structural change is observed in HCS suspension under weak shear, and accordingly, the ΔN is almost zero.     

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.     

Alkylation of 2-(methylsulfanyl)-6-polyfluoroalkylpyrimidin-4(3<Emphasis Type="Italic">H</Emphasis>)-ones with haloalkanes

The alkylation of ambident anions of 2-(methylsulfanyl)-6-(polyfluoroalkyl)pyrimidin-4(3H)-ones with 4-bromobutyl acetate leads to concurrent formation of O- and N-(4-acetoxybutyl) derivatives. Polar aprotic solvents favor formation of the O-isomer, and weakly polar dioxane favors N-alkylation. The reaction of 2-(methylsulfanyl)-6-(trifluoromethyl)pyrimidin-4(3H)-one with an equimolar amount of 1,2-dibromoethane in polar acetonitrile gives a mixture of N,N-, O,O-, and N,O-bridged bis-pyrimidines, as well as N- and O-[2-(methylsulfanyl)ethyl] derivatives, whereas in the presence of 10 equiv of 1,2-dibromoethane the N,O-isomer is formed as the only product. The reaction in weakly polar tetrahydrofuran yields N,N- and N,O-bispyrimidines.     

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.     

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.     

Synthesis of oxo derivatives of <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">p</Emphasis>-tolysulfonyl)hexahydrocycloalka[<Emphasis Type="Italic">b</Emphasis>]indoles

Hydroxymercuration-demercuration of N-p-tolysulfonyl-4,4a,9,9a-tetrahydro-3H-carbazoles and N-p-tolyl(or methyl)sulfonyl-1,3a,4,8b-tetrahydrocyclopenta[b]indoles leads to the formation of the corresponding N-p-tolylsulfonyl-2,3,4,4a,9,9a-hexahydro-1H-carbazol-2-ols and N-p-tolyl(or methyl)sulfonyl-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indol-2-ols. The latter are oxidized to 2-oxo derivatives with potassium dichromate. The oxidation of 2-methoxy-8-methyl-N-p-tolylsulfonyl-2,3,4,4a,9,9a-hexahydro-1H-carbazol-1-ol under analogous conditions gives 2-methoxy-8-methyl-N-p-tolysulfonyl-2,3,4,4a,9,9a-hexahydro-1H-carbazol-1-one.     

Effect of doping on photovoltaic characteristics of graphene

Chemical doping of CVD grown graphene by introducing PTSA (n-type) and NBD (p-type) dopants is explored. This type of doping is key building block for photovoltaic and optoelectronic devices. Doped graphene samples display (1) high transmittance in the visible and near-infrared spectrum and (2) tunable graphene sheet resistance and work function. Large area and uniform graphene films were produced by chemical vapor deposition on copper foils and transferred onto quartz as transparent substrates. For n doping, a solution of p-toluenesulfonic acid (PTSA) was first dropped and spin-coated on the graphene/quartz and then annealed at 100°C for 10 min to make graphene uniformly n-type. Subsequently, a bare graphene was transferred on another quartz substrate, a solution of 4-nitrobenzenediazonium tetrafluoroborate (NBD) was dropped and spin-coated on the surface of graphene and similarly annealed. As a result, the graphene was p and n doped on the different quartz substrates. Doped graphene samples were characterized by different techniques. Experimental results suggested that doped graphene sheets with tunable electrical resistance and high optical transparency can be incorporated into photovoltaics and optoelectronics devices.     

Effect of solvents on the morphology of NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript>/graphene nanostructures for electrochemical pseudocapacitor application

The large internal surface areas and outstanding electrical and mechanical properties of graphene have prompted to blend graphene with NiCo₂O₄ to fabricate nanostructured NiCo₂O₄/graphene composites for supercapacitor applications. The use of graphene as blending with NiCo₂O₄ enhances the specific capacitance and rate capability and improves the cyclic performance when compared to the pristine NiCo₂O₄ material. Here, we synthesized two different nanostructured morphologies of NiCo₂O₄ on graphene sheets by solvothermal method. It has been suggested that the morphologies of oxides are greatly influenced by dielectric constant, thermal conductivity, and viscosity of solvents employed during the synthesis. In order to test this concept, we have synthesized nanostructured NiCo₂O₄ on graphene sheets by facile solvothermal method using N-methyl pyrrolidone and N,N-dimethylformamide solvents with water. We find that mixture of N-methyl pyrrolidone and water solvent favored the formation of nanonet-like NiCo₂O₄/graphene (NiCoO-net) whereas mixture of N,N-dimethylformamide and water solvent produced microsphere-like NiCo₂O₄/graphene (NiCoO-sphere). Electrochemical pseudocapacitance behavior of the two NiCo₂O₄/graphene electrode materials was studied by cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy techniques. The supercapacitance measurements on NiCoO-net and NiCoO-sphere electrodes showed specific capacitance values of 1060 and 855 F g^?1, respectively, at the current density of 1.5 A g^?1. The capacitance retention of NiCoO-net electrode is 93 % while that of NiCoO-sphere electrode is 77 % after long-term 5000 charge-discharge cycles at high current density of 10 A g^?1.     

Synthesis of New Cyclopenta[<Emphasis Type="Italic">b</Emphasis>]quinoline Derivatives

A series of new 11-(R-phenyl)-8,9-dihydro-7H-benzo[f]cyclopenta[b]quinolin-10(11H)-ones and 7,14-bis(R-phenyl)-2,3,9,10,11,14-hexahydrocyclopenta[2,3]quinolino[8,7-h]cyclopenta[b]quinoline-1,8(4H,7H)-diones were synthesized by three-component condensation of naphthalen-2-amine or naphthalene- 1,5-diamine with substituted benzaldehydes and cyclopentane-1,3-dione in one step through intermediate formation of unstable arylaminoketoenol.     

Thermal Rearrangements of 3<Emphasis Type="Italic">H</Emphasis>- and 4<Emphasis Type="Italic">H</Emphasis>-Pyrazoles Prepared by Reactions of 9-Diazofluoren with Methyl Tetrolate and Methyl 3-Phenylpropiolate

9-Diazofluoren adds in Et₂O at 20°C to methyltetrolate in keeping with Auwers rule and nonregioselectively adds to methyl-3-phenylpropiolate with the formation of spirocyclic 3H-pyrazoles. The methyltetrolate adduct at boiling in toluene converts into methyl 3a-methyl-3aH-dibenzo[e,g]indazole-3-carboxylate, at 190°C in benzene, into methyl 3-methyl-2H-dibenzo[e,g]indazole-2-carboxylate, and at 160°C in methanol, into 3-methyl-2H-dibenzo[e,g]indazole. Auwers adduct of methyl 3-phenylpropiolate at boiling in benzene gives cyclopropene derivative and at boiling in methanol isomerizes into methyl 3a-phenyl-3aHdibenzo[e,g]indazole-3-carboxylate. Anti-Auwers adduct at boiling in benzene isomerizes into methyl 2-phenylpyrazolo[1,5-f]phenanthridine-3-carboxylate.     

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.     

Cyclizations of monocyclic 5-nitropyridin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones

Reactions of 5-nitropyridin-2(1H)-one and its N-methyl derivative with hydrazine hydrate led to the formation of (1H-pyrazol-3-yl) acetohydrazide. Under analogous conditions, 1,3-dimethyl-5-nitropyridin2(1H)-one gave rise to 2-(1H-pyrazol-3-yl)propionohydrazide, while 6-methyl-5-nitropyridin-2(1H)-one was converted into (5-methyl-1H-pyrazol-3-yl)acetohydrazide. Hydrazinolysis of 4-methyl-5-nitropyridin-2(1H)-one resulted in the formation of 3-methyl-4-nitro-1H-pyrazole. The mechanism of recyclization of nitropyridine derivatives by the action of hydrazine hydrate was studied using 5-nitropyridin-2(1H)-one and 1-methyl-5-nitropyridin-2(1H)-one as examples.     

Effect of <Emphasis Type="Italic">ortho</Emphasis>-methyl groups in the benzene rings of the macrocyclic frame on the chemistry of phosphacavitands

Effect of ortho-methyl groups in the benzene rings of the macrocyclic matrix on the chemistry of cavitands with phosphorous amide bridges in the upper rim is studied. The presence of ortho-methyl groups is shown to prevent formation of phosphacavitands of C _4v symmetry and favor formation of macrocyclic systems of C _2v symmetry, enhance solubility of phosphacavitands in organic solvents, hinder oxidation of phospha(III)cavitands and decrease the yield of phospha(V)cavitands, prevent formation of binuclear molybdenum complexes of phosphorous amide cavitands, and favor formation of their tetranuclear analogs.     

Reaction 5-(Arylmethylidene)pyrimidine-2,4,6(1<Emphasis Type="Italic">H</Emphasis>,3<Emphasis Type="Italic">H</Emphasis>,5<Emphasis Type="Italic">H</Emphasis>)-triones with L-Proline and Aldehydes

Boiling in toluene of 5-(arylmethylidene)pyrimidine-2,4,6(1H,3H,5H)-triones with L-proline and aldehyde led to the formation of previously unknown substituted 1′-arylhexahydro-1H-spiro[pyrimidine-5,2′-pyrrolysine]-2,4,6(1H,3Н,5Н)-triones.     

Synthesis and crystal structure of (<Emphasis Type="Italic">o</Emphasis>-Diaminobenzene)<Subscript>2</Subscript> Zn(OAc)<Subscript>2</Subscript>

The treatment of o-diaminobenzene with Zn ( OAc )₂ · 2H₂O in alcohol results in the formation of mononuclear bis(o-diaminobenzene)diacetate Zinc, Zn[C₈H₁₁N₂O₂]₂. Its structure was determined by X-ray diffraction analysis. The complex is also characterized by elemental analysis, ¹H NMR and IR. The crystal is monoclinic space group C2, parameters: a = 16.297(5), b = 4.775(3), c = 11.664(5) Å, β = 97.646(5)°, λ = 1.54184 Å, V = 899.6(7) ų, Z = 2, ρ _c = 1.476 g/cm³, M _r = 399.75, F(000) = 416.0, R ₁ = 0.0594, wR ₂ = 0.1439 for 995 observed reflections with I > 2σ(I).     

Stability of <Emphasis Type="Italic">s</Emphasis>-, <Emphasis Type="Italic">p</Emphasis>-, and <Emphasis Type="Italic">d</Emphasis>-element diphosphates in water

The mean atomic Gibbs energies of formation of (Δ _f ? _at ⁰ ) of s-, p-, and d-element diphosphates have been calculated using ion increments of the Gibbs energy (Δ _f G ⁰). The diphosphate hydrolysis kinetics is considered, and a correlation between the Δ _f ? _at ⁰ values and the hydrolysis rate constants is presented.     

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.     

Towards the optimization of carbon nanotube properties via <Emphasis Type="Italic">in situ</Emphasis> and <Emphasis Type="Italic">ex situ</Emphasis> studies of the growth mechanism

The synthesis conditions of multi-walled carbon nanotubes (MWCNTs) indirectly determine their application potential through the decisive role in the characteristics of individual tubes: diameter distribution, structure and defectiveness of graphene walls, the amount of metal impurities and amorphous carbon. In the present work, we have studied the influence of the catalyst composition and synthesis conditions on the diameter distribution and the structure of nanotube walls. We have observed the influence of the particle size for MWCNT synthesis (i.e. size effect) on catalytic activity by ex situ and in situ techniques: in situ X-ray diffraction on synchrotron radiation (SRXRD), gas chromatography, and ex situ transmission electron microscopy. The data obtained by in situ SRXRD are in agreement with the results collected using laboratory tubular fix-bed catalytic reactor allowing thereby extending the applicability of the approach. For the first time we have shown the increase of the fraction of graphene walls in the total MWCNT diameter with time.