Ultrasound and microwave assisted synthesis of isoindolo-1,2-diazine: a comparative study

A comparative study, ultrasound (US) versus microwave (MW) versus conventional thermal heating (TH), for synthesis of isoindolo-1,2-diazine is described. The reaction pathway is fast, efficient and straight applicable, involving a Huisgen [3+2] dipolar cycloaddition of cycloimmonium ylides to 1,4-naphthoquinone. A feasible reaction mechanism for the obtaining of the fully aromatized tetra- and penta- cyclic isoindolo-1,2-diazine is presented. Under US irradiation the yields are much higher (sometimes substantially, by almost double), the reaction time decreases substantially, the reaction conditions are milder. The use of a generator with a higher nominal power induces higher yields and short reaction times. Overall the use of US it proved to be more efficient than MW or TH. A feasible explication for US efficiency is presented.     

Photoluminescent properties of heteroleptic cyclometalated platinum(II) complexes bearing 1,3-bis(3,4-dibutoxyphenyl)propane-1,3-dionate as an ancillary ligand

A new series of heteroleptic cyclometalated platinum(II) complexes Pt-1a-f was synthesized, employing 2-arylpyridine (or 1-arylisoquinoline) (HC^∧N-1) and 1,3-bis(3,4-dibutoxyphenyl)propane-1,3-dione (HO^∧O-1) for cyclometalation and as ancillary ligands, respectively, and photoluminescent properties were investigated. Focusing on red-shifted phosphorescence, C^∧N ligands containing π-extended aromatics and electron-rich heterocycles were examined. All obtained complexes exhibited photoluminescence at ambient temperature, and the emission maxima ranged from green (λ_PL=518 nm) to far red (λ_PL=708 nm). The large Stokes shifts of more than 100 nm and sub-microsecond or microsecond emission lifetimes revealed that these complexes are phosphorescent emissive. The quantum yield of Pt-1 ranged from 0.02 to 0.59 at ambient temperature and decreased as the emission maximum was red-shifted. In comparison with the reference platinum(II) complexes, Pt-2 bearing an aliphatic ancillary ligand, such as 2,2,6,6-tetramethylheptane-3,5-dionate (O^∧O-2), the ligand O^∧O-1 did not significantly affect the photoluminescence emission maxima, indicating that the energy gap between the singlet ground state and the triplet level was predominantly dependent on the C^∧N ligand.     

Ultrasound promoted the synthesis of N-propargylic β-enaminones

The synthesis of 14 novel N-propargylic β-enaminones from the reaction of β-alkoxy vinyltrihalomethyl[carboxyethyl] ketones [R³C(O)CHC(R¹)OMe, where R³ = CF₃, CCl₃, CO₂Et and R¹ = Me, Et, Pr, Bu, i-Pent, CH₂CH₂CO₂Me] with propargyl amines [R²NHCH₂CCH, where R² = Pr, PhCH₂] is reported. Yields, solvents and reaction times needed for reaction completion, by microwave irradiation (MW), conventional thermal heating (TH) and under ultrasound irradiation (US) are compared. The best results were obtained under US irradiation in good to excellent yields (70-93%).     

Hydrothermal synthesis and structural characterization of (1−x)α-Fe2O3-xSnO2 nanoparticles

Structural and morphological characteristics of (1−x)α-Fe₂O₃-xSnO₂ (x=0.0-1.0) nanoparticles obtained under hydrothermal conditions have been investigated by X-ray diffraction (XRD), transmission Mössbauer spectroscopy, scanning and transmission electron microscopy as well as energy dispersive X-ray analysis. On the basis of the Rietveld structure refinements of the XRD spectra at low tin concentrations, it was found that Sn⁴⁺ ions partially substitute for Fe³⁺ at the octahedral sites and also occupy the interstitial octahedral sites which are vacant in α-Fe₂O₃ corundum structure. A phase separation of α-Fe₂O₃ and SnO₂ was observed for x≥0.4: the α-Fe₂O₃ structure containing tin decreases simultaneously with the increase of the SnO₂ phase containing substitutional iron ions. The mean particle dimension decreases from 70 to 6 nm, as the molar fraction x increases up to x=1.0. The estimated solubility limits in the nanoparticle system (1−x)α-Fe₂O₃-xSnO₂ synthesized under hydrothermal conditions are: x≤0.2 for Sn⁴⁺ in α-Fe₂O₃ and x≥0.7 for Fe³⁺ in SnO₂.     

Fabrication of water-soluble magnetic nanoparticles by ligand-exchange with thermo-responsive polymers

We report the use of thermo-responsive polymers in the synthesis of Co and γ-Fe₂O₃ nanoparticles using a two-step method involving thermal decomposition of the organometallic complexes in the presence of oleic acid and then followed by ligand-exchange process with thermo-responsive polymer. Among different thermo-responsive polymers investigated, it was found that the polymer based on poly(N-isopropylacrylamide) with a co-monomer component of acrylic acid and acrylamide can be used in the ligand-exchange to coat Co and γ-Fe₂O₃ nanoparticles, respectively. The nanoparticles are found to be water-soluble at temperatures below coil-to-globule phase transition of the coating polymer.     

Ultrasound-assisted one-pot green synthesis of new N- substituted-5-arylidene-thiazolidine-2,4-dione-isoxazoline derivatives using NaCl/Oxone/Na3PO4 in aqueous media

A rapid and green method for the synthesis of novel N-thiazolidine-2,4-dione isoxazoline derivatives 5 from N-allyl-5-arylidenethiazolidine-2,4-diones 3 as dipolarophiles with arylnitrile oxides via 1,3-dipolar cycloaddition reaction. The corresponding N-allyl substituted dipolarophiles were prepared by one-pot method from thiazolidine-2,4-dione with aldehydes using Knoevenagel condensation followed by N-allylation of thiazolidine-2,4-dione in NaOH aqueous solution under sonication. In addition, the isoxazoline derivatives 5 were synthesized by regioselective and chemoselective 1,3-dipolar cycloaddition using inexpensive and mild NaCl/Oxone/Na₃PO₄ as a Cl source, oxidant and/or catalyst under ultrasonic irradiation in EtOH/H₂O (v/v, 2:1) as green solvent. All synthesized products are furnished in good yields in the short reaction time, and then their structures were confirmed by NMR, mass spectrometry and X-ray crystallography analysis.     

High-resolution X-ray emission <Emphasis Type="Italic">M</Emphasis>α and <Emphasis Type="Italic">M</Emphasis>β spectra of Bi atoms

The structure and relative intensity of x-ray fluorescence Mα and Mβ spectra of Bi atoms have been studied experimentally under excitation by Cr and Cu Kα_1,2 radiation. It has been found that observed short-wavelength satellites are mostly caused by the radiative transitions M ₅ N-N _6,7 N (M ₅ N satellites) and M ₄ N-N ₆ N (M ₄ N satellites), whereas the transitions M ₅ O-N _6,7 O and M ₄ O-N ₆ O are overlapped with the profiles of x-ray diagram Mα_1,2 and Mβ lines and are not observed as individual structures. The M ₅ N and M ₄ N satellites have been separated from total spectral profiles, and the relative intensities of such groups of lines have been determined. A model has been proposed for calculation of emission cross sections of the M ₄ N and M ₄ N satellites, as well as the Mα_1,2 lines along with the M ₅ O satellites and the Mβ line with the M ₄ O satellites. The model takes into account main channels of generation and migration of vacancies in M subshells connected with the Coster-Kronig transitions M _i -M _j N and M _i -M _j O, radiative transitions M _i -M _j and M _i -N _j , and shaking processes upon production of the M _i vacancy, as well as with cascades of such processes. Comparison of experimental values of the relative intensity of the separated satellites with calculated results indicates the correctness of the model used.     

Design,synthesis, and anti-tobacco mosaic virus (TMV) activity of glycoconjugates of phenanthroindolizidines alkaloids

Glycoconjugates of phenanthroindolizidine alkaloids targeting tobacco mosaic virus (TMV) RNA were designed, synthesized, and evaluated for their antiviral activity against TMV for the first time. The glycoconjugation of $(S)$ -6-O-desmethylantofine (2) and 14-hydroxyltylophorines (3–6) was accomplished in three ways (O-glycosylation manner, using carbamoyloxy as linker arm, and using 1,2,3-triazole as linker arm) with three different sugar units (glucose, galactose, and mannose). The glycoconjugates showed improved water solubility and molecule polarity compared with phenanthroindolizidine alkaloids. The bioassay results showed that C6 was a suitable position for glycoconjugation and O-glycosylation can increase the antiviral activity of phenanthroindolizidine alkaloids indicating that the introduction of sugar units can improve the antiviral activity profile of glycoconjugates. Two O-glycosides of $(S)$ -6-O-desmethylantofine, (13aS)-6-O- $\upbeta $ -d-galactopyranosyl-2,3-dimethoxyphenanthro [9,10-b]-11-indolizidinone (10) and (13aS)-6-O- $\upbeta $ -d-mannopyranosyl-2,3-dimethoxyphenanthro [9,10-b]-11-indolizidinone (11) displayed significant higher activity than commercial ningnanmycin, and thus could be considered for novel therapy against plant virus infection.     

Redox reactions of K3[Fe(CN)6] during mechanochemically stimulated phase transitions of AlOOH

Thermally induced redox reactions of K₃[Fe(CN)₆] (1) were investigated for a broad temperature range by thermal methods and structure analytical methods (ESR and Mößbauer spectroscopy, X-ray Powder diffraction and XANES). Based on the influence of the mechanically activated and transforming matrices 2 and 3, redox processes can be tuned to form doped Al₂O₃ systems which contain either isolated Fe³⁺ centres or redox active phases and precursors like (Al_1−xFe_x)₂O₃ (4), (Al_3−xFe_x)O₄ (5), Fe₃O₄, Fe₂O₃ and Fe⁰. The phase Fe₃C and the chemically reactive C-species were detected during the reaction of 1. The final composition of the doped products of α-Al₂O₃ is mainly influenced by the chemical nature of the Fe doping component, the applied temperature and time regime, and the composition of the gas phase (N₂, N₂/O₂ or N₂/H₂). From the solid state chemistry point of view it is interesting that the transforming matrix (2 and 3) possesses both oxidative and protective properties and that the incorporation of the Fe species can be performed systematically.     

AC impedance spectroscopic studies of transport properties in metal oxide doped α-NPD

The potential application of molecular organic semiconductor needs the control adjustment of conductivity. The hole transport materials (HTL) α-NPD (N,N′-di(1-naphthyl)-N,N′-diphenylbenzidin) has been doped with metal oxide (molybdenum oxide) for the study of transport phenomena. Impedance spectroscopic measurements were performed with the applied external electric filed. The activation energy calculated (0.55, 0.48 and 0.50 eV) decreases with doping of metal oxide. There is a clear indication of space charge limited (SCL) conduction in the doped and undoped thin films. The cole–cole plot indicates the device can be represented by a parallel resistance and capacitance network in series with a series resistance (of 70 Ω). At high frequency; the conduction follows the universal power law for both doped–undoped α-NPD with MoO₃ and the onset frequency increases with increasing bias voltages. The conduction mechanism can be explained by classical hopping barriers (CHB) mechanism for the system.     

Synthesis and solid state NMR characterization of novel peptide/silica hybrid materials

The successful synthesis and solid state NMR characterization of silica-based organic–inorganic hybrid materials is presented. For this, collagen-like peptides are immobilized on carboxylate functionalized mesoporous silica (COOH/SiO_x) materials. A pre-activation of the silica material with TSTU (O-(N-Succinimidyl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate) is performed to enable a covalent binding of the peptides to the linker. The success of the covalent immobilization is indicated by the decrease of the ¹³C CP-MAS NMR signal of the TSTU moiety. A qualitative distinction between covalently bound and adsorbed peptide is feasible by ¹⁵N CP-MAS Dynamic Nuclear Polarization (DNP). The low-field shift of the ¹⁵N signal of the peptide's N-terminus clearly identifies it as the binding site. The DNP enhancement allows the probing of natural abundance ¹⁵N nuclei, rendering expensive labeling of peptides unnecessary.     

Synthesis,characterization and luminescence study of dimethyl[N-arylmethylenethiobenzahydrazonato]indium

Five dimethylindium complexes of type Me₂InL [L = N-(4-methoxy)benzylidenethiobenzahydrazonato (1), N-(3,4-dimethoxy)benzylidenethiobenzahydrazonato (2), N-(4-N,N-dimethylamino)benzylidenethiobenzahydrazonato (3), N-(2-naphthyl)methylene thiobenzahydrazonato (4) and N-(9-anthryl)methylenethiobenzahydrazonato (5)] have been synthesized by reaction of trimethylindium with appropriate N-arylmethylenethiobenzahydrozones. The complexes obtained have been characterized by elemental analysis, ¹H NMR, IR and mass spectroscopy. Compounds 1–5 emit blue colors at λ_max = 432–479 nm when irradiated by UV light. The electroluminescent (EL) properties of 1–5 were examined by fabricating EL devices using 1–5 as emitter, respectively. The EL bands are located in the green region (513–578 nm).     

A f acile,regioselective synthesis of novel 3-( N-phenylc arbox amide)pyr azolo[1,5- a]pyrimidine an alogs in the presence of KHSO$$_{}$$ in aqueous medi a assisted by ultr asound and their antib acteri al activities

An environmentally benign, simple, efficient, and convenient route is described for the synthesis of novel pyrazolo[1,5-a]pyrimidine derivatives under ultrasound irradiation. Condensation of aminopyrazole 5 with formylated active proton compounds (6, 8, E–G, 12, and 15) furnished pyrazolopyrimidine (7, 9, 10, 13, and 16) in high-to-excellent yields. In comparison with conventional methods, ultrasound irradiation offers several advantages, such as shorter reaction time, higher yields, milder conditions, and environmental friendliness. The reaction is clean with excellent yields and reduces the use of solvents. X-ray crystallographic study of compound 7c confirmed the regioselectivity of the reaction. The antibacterial profile of the newly synthesized compounds was evaluated by cup and saucer method.     

Visible light activated photo-catalytic effect and local structure of iron silicate glass prepared by sol-gel method

A relationship between methylene blue (MB) decomposition ability under visible light and local structure of xFe₂O₃·(100-x)SiO₂ glass abbreviated as xFS prepared by sol-gel method was investigated by ⁵⁷Fe-Mössbauer spectroscopy, X-ray diffractometry (XRD) and ultraviolet-visible light absorption spectroscopy (UV-Vis). Mössbauer spectra of xFS glass with x of 10, 30 and 50 annealed at 1000 °C for 3 h were mainly composed of a paramagnetic doublet due to fayalite (Fe₂SiO₄), and magnetic sextets due to magnetite (Fe₃O₄) or hematite (α-Fe₂O₃). The absorption area (A) of α-Fe₂O₃ gradually increased from 0.0 to 10.3 and 100 % with the increasing Fe₂O₃ content (x) of annealed xFS glass. A leaching test performed by 20 mL of MB aqueous solution and 40 mg of annealed 50FS glass showed that MB concentration decreased from 16.2 to 4.7 μmol L^?1 after 2 h with the first order rate constant of 1.8 × 10^?4 s^?1. These results prove that annealed iron silicate glass containing α-Fe₂O₃ can decompose MB effectively under visible light irradiation.     

Cycloaddition of 2′-azidoethyl glycosides to fullerene[C60] under ultrasonic irradiation

The reactions of fullerene[C₆₀] with 2′-azidoethyl 2,3,4,6-tetra-O-acetyl-α-d-mannopyranoside (2a) and 2′-azidoethyl 2,3,4,6-tetra-O-acetyl-β-d-galactopyranoside (2b) under ultrasonic irradiation cause the cycloaddition of 2′-azidoethyl glycosides to fullerene[C₆₀] and lead to d-glycosyl fullerene[C₆₀] derivatives 3a and 3b, respectively. The glycosyl fullerene[C₆₀] derivatives were characterized by ¹H and ¹³C NMR, UV–vis, FAB-MS, FT-IR spectra and were a 1:1 glycoside fullerene [C₆₀]-adduct.     

On the Negative Spectrum of the Two-Dimensional Schrödinger Operator with Radial Potential

For a two-dimensional Schrödinger operator H _{α V}  = ?Δ ?αV with the radial potential V(x) = F(|x|), F(r) ≥ 0, we study the behavior of the number N _?(H _{α V} ) of its negative eigenvalues, as the coupling parameter α tends to infinity. We obtain the necessary and sufficient conditions for the semi-classical growth N _?(H _{α V} ) = O(α) and for the validity of the Weyl asymptotic law.     

Fast integral equation methods for the modified Helmholtz equation

We present integral equation methods for the solution to the two-dimensional, modified Helmholtz equation, u(x) ? α²Δu(x) = 0, in bounded or unbounded multiply-connected domains. We consider both Dirichlet and Neumann problems. We derive well-conditioned Fredholm integral equations of the second kind, which are discretized using high-order, hybrid Gauss-trapezoid rules. Our fast multipole-based iterative solution procedure requires only O(N) operations, where N is the number of nodes in the discretization of the boundary. We demonstrate the performance of our methods on several numerical examples, and we show that they have both the ability to handle highly complex geometry and the potential to solve large-scale problems.     

Hydrolysis precipitation synthesis of monodisperse α-Fe2O3 nanorods/graphene oxide nanocomposites

A nanocomposite of graphene oxide supported by monodisperse rod-like α-Fe₂O₃ nanocrystals (GO/α-Fe₂O₃ nanocomposites) has been fabricated through a simple hydrolysis precipitation route in a water–ethanol system. The nanocomposites were characterized by X-ray diffraction, Raman spectra and transmission electron microscopy, respectively. The GO/α-Fe₂O₃ nanocomposites are GO nanosheets decorated randomly by α-Fe₂O₃ nanorods with diameters in the range of 3–5 nm and lengths of 20–30 nm, while only hollow α-Fe₂O₃ microspheres constructed by the radically oriented single-crystalline nanorods are observed in the absence of GO. Compared with pure α-Fe₂O₃ nanoparticles, α-Fe₂O₃/GO nanocomposites exhibited excellent photocatalytic activity as evident from the degradation of rhodamine B in water under UV irradiation. The superior photocatalytic activity performance of α-Fe₂O₃/GO nanocomposites could be attributed to the synergetic effect between the conducting GO nanosheets and monodisperse α-Fe₂O₃ nanorods.     

Inhibition performance of 2-mercaptobenzothiazole derivatives in CO2 saturated solution and its adsorption behavior at Fe surface

Two 2-mercaptobenzothiazole derivatives, N,N′-bis-(2-thionobenzothiazolin-3-yl-methyl)-n-dodecylamine (BTBMDA) and N,N′-bis-(2-thionobenzothiazolin-3-yl-methyl)-n-octadecylamine (BTBMOA), were synthesized under microwave irradiation. Their inhibition performance for N80 steel in CO₂ saturated solution at 90 °C were tested by weight loss method and the surface analysis was performed by SEM. The adsorption behavior of two inhibitors at the Fe surface was studied by the molecular dynamics simulation method and the quantum chemistry calculations. Results showed that the two inhibitors could inhibit the corrosion of N80 steel in simulated solution significantly. There were two types of end configurations for two inhibitors at the Fe surface in the molecular dynamics simulation, and the two inhibitors adsorbed at the surface mainly through one of the two types.     

Synthesis and drug-loading properties of folic acid-modified superparamagnetic Fe3O4 hollow microsphere core/mesoporous SiO2 shell composite particles

Magnetic nanoparticles with immobilized metal ligands were prepared for the separation of antibody fragments. First, iron oxide nanoparticles were produced in a solvothermal synthesis using triethylene glycol as solvent and iron(III) acetylacetonate as organic precursor. Via functionalization of the particles with priorly reacted 3-glycidoxypropyltrimethoxysilane and N α,N α-bis(carboxymethyl)-l-lysine (NTA), and charging with Ni²⁺, magnetic affinity adsorbents were obtained. The particles were applied to separate a His-tagged antibody fragment from a heterogeneous protein mixture of a microbial cultivation supernatant. Binding properties and specificity for purification of the target product ABF D1.3 scFv were optimized regarding the GNTA concentration and were found superior as compared to commercially available systems. A molar ratio of 1:2 Fe₂O₃:GNTA was most beneficial for the specific purification of the antibody fragment.