An efficient one-pot synthesis of pyrazolyl-[1,2,4]triazolo[3,4-b][1,3,4] thiadiazin-6-yl)-2H-pyran-2-one derivatives via multicomponent approach and their potential antimicrobial and nematicidal activities

A series of simple or/and aryl, heteryl hydrazono pyrazolyl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-6-yl)-2H-pyran-2-one derivatives have been efficiently synthesized in excellent yields via one-pot, multi-component approach. The importance of this methodology is that in a one-pot operation four new bonds (3C–N and 1C–S) are generated. The structure of compound 5a was confirmed by single-crystal X-ray diffraction. The newly synthesized compounds were evaluated for their in vitro antimicrobial activity against gram-positive bacteria (Staphylococcusaureus and Bacillussubtilis), gram-negative bacteria (Escherichiacoli andKlebsiellapneumoniae), antifungal activity against Candida albicans, and nematicidal activity against Meloidogyneincognita. Among all the compounds 6f showed excellent antimicrobial and nematicidal activity against tested bacteria, fungi, and nematodes.     

Synthesis and antibacterial activity of novel 10, 11-epoxy acylide erythromycin derivatives

A series of novel acylide derivatives have been synthesized from clarithromycin A via a facile procedure. The C-3 modifications involved replacing the natural C-3 cladinosyl group in clarithromycin core with different aryl-piperzine sidechain via chemical synthesis. Meanwhile a distinctive intermediate with 10,11-epoxy moiety was obtained. The structure and stereochemistry of this novel structure were confirmed via NMR and X-ray crystallography. Potential anti-bacterial activities against both Grampositive and Gram-negative bacteria were reported. Because of existence of C10,11-epoxide, these derivatives can be used as intermediates for further structural modification.     

Oxygen self-diffusion in single-crystal MgO: secondary-ion mass spectrometric analysis with comparison of results from gas–solid and solid–solid exchange

Self-diffusion coefficients for ¹⁸O in single-crystal MgO have been determined from a novel specimen comprising an epitaxial layer of high-purity Mg¹⁸O upon a single crystal substrate of normal MgO. Heating the specimen in air produced a gas–solid exchange gradient at the sample surface as ¹⁸O in the epitaxial layer exchanged with ¹⁶O in air. A solid–solid interdiffusion gradient was produced between the substrate crystal and the ¹⁸O-enriched epitaxial layer. SIMS analysis of gas–solid exchange gradients prepared in the temperature range 1000–1650 °C provided diffusion coefficients that could be described as

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. Interdiffusion gradients produced by annealing at 1100 and 1200 °C yielded the self-diffusion coefficients that were comparable to those obtained from gas–solid exchange, indicating that the surface exchange reaction is fast enough. The results are interpreted in terms of a defect model in which oxygen diffusion occurs by an interstitial type of defect as a result of suppression of anion vacancy concentration by large concentrations of extrinsic cation vacancies.     

Synthesis and structure of a new halophosphate Sr3P3O10Cl with the flexible [P3O10]5− anions

A new halophosphate crystal Sr₃P₃O₁₀Cl was grown in molten chloride flux media. It crystallizes in the centrosymmetric orthorhombic space group Pnma (No. 62) with a = 10.617(2) Å, b = 10.736(2) Å, and c = 8.7354(17) Å. In the structure, the basic building unit is the [P₃O₁₀]⁵⁻ anion, which is consist of three PO₄ tetrahedra by sharing the corner oxygen atoms. The two Sr atoms and the Cl atom are linked to construct an infinite [Sr₃Cl]⁵⁺ chain. The [P₃O₁₀]⁵⁻ anions are interconnected with the [Sr₃Cl]⁵⁺ chains to form a three-dimensional frameworks. Additionally, the first-principle calculation was employed to obtain the band structures and densities of states.     

Single-crystal electronic spectra of some quadrate chromium(III) complexes

Polarised electronic spectra of trans-[Cr(tmd)₂F₂](ClO₄), trans-[Cr(en)₂(dma)₂](ClO₄)₃, trans-[Cr(en)₂(dmf)Cl](ClO₄)₂ and trans-[Cr(en)₂(dmf)Br](ClO₄)₂ have been measured at 77 K (tmd = trimethylenediamine; dma = N,N-dimethylacetamide; dmf = N,N-dimethylformamide; en = ethylenediamine, pn = propylenediamine). The observed quartet bands have been given definitive quadrate assignments based on polarisation characteristics. The four-component quadrate quartet bands have been uncovered and assigned also in the unpolarised crystal spectrum of trans-[Cr(en)₂(dmf)₂](ClO₄)₃ at 77 K and the solution spectrum of trans-[Cr(en)(pn)F₂]⁺. The band maxima derived by gaussian analysis in these spectra have been fitted with the theoretical energy equations of d³ configuration in quadrate ligand fields including full configuration interaction. The ligand field parameters Dq, Dt, and Ds and the election correlation parameter, B, extracted by such a fitting, have been compared with those obtained for other similar systems earlier. The significance of the ligand field symmetry parameters and the translated angular overlap model parameters is discussed.     

Crystal structure and luminescence of Sr0.99Eu0.01AlSiN3

Strontium europium aluminum silicon nitride, Sr_0.99Eu_0.01AlSiN₃, was synthesized by heating a mixture of binary nitrides at 2173 K and a N₂ gas pressure of 190 MPa. Single crystals of Sr_0.99Eu_0.01AlSiN₃ approximately 30 μm were obtained. The structure was confirmed to be an isotypic structure of CaAlSiN₃ in the orthorhombic space group Cmc2₁, analyzed by single-crystal X-ray diffraction. The lattice parameters are a=9.843(3), b=5.7603(16), c=5.177(2) Å, cell volume=293.53(17) Å³. It shows an orange-red photoluminescence by 5d→4f transition of Eu²⁺ at around 610 nm under excitation ranging from ultraviolet to 525 nm. The photoluminescence intensity, temperature characteristics, and oxidative stability were comparable or superior to those of CaAlSiN₃:Eu²⁺ phosphor.     

Potentiometric sensor for the nanoscale monitoring of Ni2+ ion in environmental samples by the fabrication of coated pyrolytic graphite electrode based on a novel C–C-coupled compound

Novel ligand 5,5?-((3-nitrophenyl)methylene)bis(2,6-diaminopyrimidin-4(3H)-one) (L) was synthesised and characterised. Preliminary studies on L have showed that it has more affinity towards the Ni²⁺ ion. Thus, the L was used as the electroactive material in the fabrication of poly(vinyl chloride) (PVC)-based membrane sensors such as coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE). Several polymeric membranes were fabricated by incorporating L as ionophore, NaTPB as anion excluders and BA, 1-CN, DBP, DOP and o-NPOE as solvent mediators and their effect on potentiometric response studied. Comparative electroanalytical studies performed on the CGE and CPGE depict that the CPGE with optimised membrane composition of L:PVC:o-NPOE:NaTPB in the ratio of 7:33:58:2 (w/w, mg) exhibited the best response in terms of wide working concentration range from 2.0 × 10^?8 to 1.0 × 10^?1 mol L^?1, (3.64 µg L^?1 –18.2 g L^?1) lower detection limit of 8.1 × 10^–9 mol L^?1 (1.47 µg L^?1) with Nernstian compliance of 29.4 ± 0.2 mV decade^?1 of activity of Ni²⁺ ion in the pH range of 3.5–9.0. The sensor can work satisfactorily in water–acetonitrile and water–methanol mixtures. It can tolerate 30% acetonitrile and 20% methanol content in the mixtures. The sensor showed fast response time of 8 s and could be used successfully for a period of 4 months. The sensor reflects its utility in the quantification of Ni²⁺ ion in real samples and has been successfully employed as an indicator electrode in the potentiometric titration of Ni²⁺ ion with EDTA.     

Synthesis of single-crystal silver slices with predominant (1 1 1) facet and their SERS effect

In this article, single-crystal silver slices with predominant (1 1 1) facet were synthesized at room temperature with chitosan by a facile, one-pot, and totally green method. XRD, UV-visible and infrared spectroscopy have been employed for identifying chitosan-protected silver nanoparticles (NPs), while SEM, TEM were used to confirm silver NPs orientation along the (1 1 1) direction to form various shapes such as hexagon, trapezium, triangle and so on. The results showed that chitosan, a novel environmentally benign and excellently biocompatible material, serves not only as a reducing agent but also as a stabilizer for the growth of anisotropic silver NPs. The single-crystal silver slices with major facet of (1 1 1) can be used as a surface-enhanced Raman scattering (SERS) substrate, and crystal violet (CV) as a Raman probe to evaluate its enhancement ability. It was found that the enhancement ability of the silver slices was remarkable.     

Synthesis and spectroscopic characterization of eleven mixed-ligand diorganotellurium(IV) compounds containing dithiocarbamate and dithiophosphate ligands

Eleven mixed-ligand organotellurium(IV) compounds of composition R₂Te(dtc)(dtp) have been prepared employing two different dithiocarbamate (dtc) and dithiophosphate (dtp) ligands: 1, R₂ = C₄H₈, dtc = S₂CNEt₂, dtp = S₂P(OCH₂)₂CEt₂; 2, R₂ = C₈H₈, dtc = S₂CNEt₂, dtp = S₂P(OCH₂)₂CEt₂; 3, R₂ = C₄H₈O, dtc = S₂CNEt₂, dtp = S₂P(OCH₂)₂CEt₂; 4, R₂ = C₅H₁₀, dtc = S₂CNEt₂, dtp = S₂P(OCH₂)₂CEt₂; 5, R₂ = C₄H₈, dtc = S₂CN(CH₂)₄, dtp = S₂P(OCH₂)₂CEt₂; 6, R₂ = C₈H₈, dtc = S₂CN(CH₂)₄, dtp = S₂P(OCH₂)₂CEt₂; 7, R₂ = C₄H₈O, dtc = S₂CN(CH₂)₄, dtp = S₂P(OCH₂)₂CEt₂; 8, R₂ = C₅H₁₀, dtc = S₂CN(CH₂)₄, dtp = S₂P(OCH₂)₂CEt₂; 9, R₂ = C₄H₈, dtc = S₂CN(CH₂)₄, dtp = S₂P(OCH₂)₂CMeⁿPr; 10, R₂ = C₈H₈, dtc = S₂CN(CH₂)₄, dtp = S₂P(OCH₂)₂CMeⁿPr; 11, R₂ = C₄H₈O, dtc = S₂CN(CH₂)₄, dtp = S₂P(OCH₂)₂CMeⁿPr. 1-11 were characterized by mass spectrometry, IR spectroscopy and multinuclear NMR (¹H, ¹³C, ³¹P, ¹²⁵Te) spectroscopy. The molecular structures of 2, 4 and 6, of which 2 crystallized in form of two different polymorphs (2a and 2b), were analyzed by single-crystal X-ray diffraction analysis. This analysis showed that the coordination mode of both ligand types is anisobidentate. When considering only covalent Te-C and Te-S bonds, the coordination geometry of the tellurium atoms is distorted Ψ-trigonal-bipyramidal, since the lone pair is stereochemically active and occupies an equatorial position together with the carbon atoms of the tellurocycles. If secondary Te?S interactions are considered also, the coordination sphere around tellurium is best described as bicapped Ψ-trigonal-bipyramidal for the complexes with two intramolecular Te?S secondary bonds and monomeric molecular structures, and pentagonal-bipyramidal for the complexes in which neighboring molecules in the crystal lattice are linked through additional weak intermolecular Te?S secondary bonds to form dimeric supramolecular aggregates.     

Synthesis, structural characterization and magnetic properties of RE2MgGe2 (RE=rare-earth metal)

A series of rare-earth metal–magnesium–germanides RE₂MgGe₂ (RE=Y, Nd, Sm, Gd–Tm, Lu) has been synthesized by reactions of the corresponding elements at high temperature. Their structures have been established by single-crystal and powder X-ray diffraction and belong to the Mo₂FeB₂ structure type (space group P4/mbm (No. 127), Z=2; Pearson symbol tP10). Temperature dependent DC magnetization measurements indicate Curie–Weiss paramagnetism in the high-temperature regime for all members of the family, excluding Y₂MgGe₂, Sm₂MgGe₂, and Lu₂MgGe₂. At cryogenic temperatures (ca. 60 K and below), most RE₂MgGe₂ phases enter into an antiferromagnetic ground-state, except for Er₂MgGe₂ and Tm₂MgGe₂, which do not undergo magnetic ordering down to 5 K. The structural variations as a function of the decreasing size of the rare-earth metals, following the lanthanide contraction, and the changes in the magnetic properties across the series are discussed as well.