Luminescence Properties of Tb-Doped Yttrium Disilicate Prepared by the Sol–Gel Method

A sol–gel method for the synthesis of nanosized powders of yttrium disilicate doped with Tb^{3 +} is presented. The influence of grain size and annealing temperature on the structure and luminescence properties of the materials obtained has been investigated. The preparation of glass-ceramic composite has been also described. The effect of incorporating the nanocrystals into sol–gel silica glasses on their physicochemical properties has been shown and discussed. A lack of influence of the annealing above 1300°C on the lifetimes measured for the nanocrystals embedded in the glass, as compared to the Y₂Si₂O₇:Tb^{3 +} powders, has been observed.     

The de novo design of median molecules within a property range of interest

Summary In this paper an application is presented of the median molecule workflow to the de novo design of novel molecular entities with a property profile of interest. Median molecules are structures that are optimised to be similar to a set of existing molecules of interest as an approach for lead exploration and hopping. An overview of this workflow is provided together with an example of an instance using the similarity to camphor and menthol as objectives. The methodology of the experiments is defined and the workflow is applied to designing novel molecules for two physical property datasets: mean molecular polarisability and aqueous solubility. This paper concludes with a discussion of the characteristics of this method.     

Recent trends in mass spectrometer development

Trends in mass analyzer development are reviewed here with an emphasis on tandem mass spectrometers. The move toward hybridization of conventional mass analyzers to allow additional instrument functionality in tandem mass spectrometry is discussed.     

Lanthanide Complexes with Multidentate Oxime Ligands as Single‐Molecule Magnets and Atmospheric Carbon Dioxide Fixation Systems

The synthesis, structure, and magnetic properties of five lanthanide complexes with multidentate oxime ligands are described. Complexes 1 and 2 ( 1 : [La₂(pop)₂(acac)₄(CH₃OH)], 2 : [Dy₂(pop)(acac)₅]) are synthesized from the 2‐hydroxyimino‐N‐[1‐(2‐pyridyl)ethylidene]propanohydrazone (Hpop) ligand, while 3 , 4 , and 5 ( 3 : [Dy₂(naphthsaoH)₂(acac)₄H(OH)]?0.85 CH₃CN?1.58 H₂O; 4 : [Tb₂(naphthsaoH)₂(acac)₄H(OH)]?0.52 CH₃CN?1.71 H₂O; 5 : [La₆(CO₃)₂(naphthsao)₅ (naphthsaoH)_0.5(acac)₈(CO₃)_0.5(CH₃OH)_2.76H_5.5(H₂O)_1.24]?2.39 CH₃CN?0.12 H₂O) contain 1‐(1‐hydroxynaphthalen‐2‐yl)‐ethanone oxime (naphthsaoH₂). In 1 – 4 , dinuclear [Ln₂] complexes crystallize, whereas hexanuclear La^III complex 5 is formed after fixation of atmospheric carbon dioxide. Dy^III‐based complexes 2 and 3 display single‐molecule‐magnet properties with energy barriers of 27 and 98 K, respectively. The presence of a broad and unsymmetrical relaxation mode observed in the ac susceptibility data for 3 suggest two different dynamics of the magnetization which might be a consequence of independent relaxation processes of the two different Dy³⁺ ions.     

Spectral,thermal, molecular modeling and biological studies on mono- and binuclear complexes derived from oxalo bis(2,3-butanedionehydrazone)

Background

Hydrazones and their metal complexes were heavily studied due to their pharmacological applications such as antimicrobial, anticonvulsant analgesic, anti-inflammatory and anti-cancer agents. This work aims to synthesize and characterize novel complexes of VO²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Zr⁴⁺and Pd²⁺ ions with oxalo bis(2,3-butanedione-hydrazone). Single crystals of the ligand have been grown and analyzed.

Results

Oxalo bis(2,3-butanedionehydrazone) [OBH] has a monoclinic crystal with P 1 21/n 1 space group. The VO²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Zr⁴⁺ and Pd²⁺ complexes have the formulas: [VO(OBH–H)₂]·H₂O, [Co(OBH)₂Cl]Cl·½EtOH, [Ni₂(OBH)Cl₄]·H₂O·EtOH, [Cu(OBH)₂Cl₂]·2H₂O, [Zn(OBH–H)₂], [Zr(OBH)Cl₄]·2H₂O, and [Pd₂(OBH)(H₂O)₂Cl₄]·2H₂O. All complexes are nonelectrolytes except [Co(OBH)₂Cl]Cl·½EtOH. OBH ligates as: neutral tetradentate (NNOO) in the Ni²⁺ and Pd²⁺ complexes; neutral bidentate (OO) in [Co(OBH)₂Cl]Cl·½EtOH, [Zr(OBH)Cl₄]·2H₂O and [Cu(OBH)₂Cl₂]·2H₂O and monobasic bidentate (OO) in the Zn²⁺ and VO²⁺ complexes. The NMR (¹H and ¹³C) spectra support these data. The results proved a tetrahedral for the Zn²⁺ complex; square-planar for Pd²⁺; mixed stereochemistry for Ni²⁺; square-pyramid for Co²⁺ and VO²⁺ and octahedral for Cu²⁺ and Zr⁴⁺ complexes. The TGA revealed the outer and inner solvents as well as the residual part. The molecular modeling of [Ni₂(OBH)Cl₄]·H₂O·EtOH and [Co(OBH)₂Cl]Cl·½EtOH are drawn and their molecular parameters proved that the presence of two metals stabilized the complex more than the mono metal. The complexes have variable activities against some bacteria and fungi. [Zr(OBH)Cl₄]·2H₂O has the highest activity. [Co(OBH)₂Cl]Cl·½EtOH has more activity against Fusarium.

Conclusion

Oxalo bis(2,3-butanedionehydrazone) structure was proved by X-ray crystallography. It coordinates with some transition metal ions as neutral bidentate; mononegative bidentate and neutral tetradentate. The complexes have tetrahedral, square-planar and/or octahedral structures. The VO²⁺ and Co²⁺ complexes have square-pyramid structure. [Cu(OBH)₂Cl₂]·2H₂O and [Ni₂(OBH)Cl₄]·H₂O·EtOH decomposed to their oxides while [VO(OBH–H)₂]·H₂O to vanadium. The energies obtained from molecular modeling calculation for [Ni₂(OBH)Cl₄]·H₂O·EtOH are less than those for [Co(OBH)₂Cl]Cl·½EtOH indicating the two metals stabilized the complex more than mono metal. The Co(II) complex is polar molecule while the Ni(II) is non-polar.

Graphical abstract

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Decoration of multi-walled carbon nanotubes with NiO nanoparticles and investigation on their catalytic activity to synthesize pyrimidinone heterocycles

A supported carbon material is shown to be a highly efficient, eco-friendly and recyclable solid acid catalyst for the Biginelli reaction of aldehyde, β-ketoester and urea or thiourea under microwave irradiation in the absence of solvent. This method offers significant advantages such as efficiency, the excellent yield, avoidance of the organic solvents, mild reaction conditions, easy separation and simple operation. In addition, because of employing microwave as heating source and reducing use of organic solvents, this novel method emerges as a green-approach leading to less harmful residues. Furthermore, a mechanism was proposed to rationalize the reaction and the role of NiO–MWCNTs was also investigated in these transformations.     

Spectroscopic and structural characterization of pure and FeCl<Subscript>3</Subscript>-containing tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate

The spectroscopic properties and liquid structure of pure tri-n-butyl phosphate (TBP) and FeCl₃/TBP solutions have been investigated by Uv–Vis and Raman spectroscopies, X-ray diffraction and conductometry. Uv–Vis and Raman spectra, supported by conductometric measurements, consistently indicate that the solubilized salt is present mostly as TBP _n [FeCl_3???n ] ⁿ⁺ and FeCl₄ ^? complex ions due to specific interaction with the TBP phosphate group. Thanks to this interaction, a high amount of salt (up to 13 % w/w) can be dissolved despite the relatively low dielectric constant of TBP. The X-ray diffractogram of pure TBP has been interpreted in terms of three main contributions which can be attributed to spatial pair correlations between atoms of interacting TBP molecules. In the presence of increasing FeCl₃ amounts, it has been observed a progressive structuring effect, exerted by the dissolved salt, on the layers of opportunely oriented TBP molecules due to the formation of the complex ionic species. By simple treatment with NaBH₄, the synthesis of Fe nanoparticles has been achieved. The absence of water, the easiness of preparation, the high amount of salt which can be suspended and the peculiar physico-chemical properties of such systems are all elements worth of note for the fields of nanoparticle synthesis and for specialized technological applications.     

Mononuclear transition and non-transition complexes of amlodipine besylate as antihypertensive agent: synthesis,spectral, thermal,and antimicrobial studies

Mononuclear Mn(II), Co(II), Ni(II), Zn(II), Cd(II), Mg(II), Sr(II), Ba(II), Ca(II), Pt(IV), Au(III), and Pd(II) complexes of the drug amlodipine besylate (HL) have been synthesized and characterized by elemental analysis, spectroscopic technique (IR, UV–Vis, solid reflectance, scanning electron microscopy, X-ray powder diffraction, and ¹H-NMR) and magnetic measurements. The elemental analyses of the complexes are confirmed by the stoichiometry of the types [M(HL)(X)₂(H₂O)]·nH₂O [M = Mn(II), Co(II), Zn(II), Ni(II), Mg(II), Sr(II), Ba(II), and Ca(II); X = Cl^? or NO₃ ^?], [Cd(HL)(H₂O)]Cl₂, [Pd(HL)₂]Cl₂, [Pt(L)₂]Cl₂, and [Au(L)₂]Cl, respectively. Infrared data revealed that the amlodipine besylate drug ligand chelated as monobasic tridentate through NH₂, oxygen (ether), and OH of besylate groups in Mn(II), Co(II), Ni(II), Zn(II), Cd(II), Mg(II), Sr(II), Ba(II), Ca(II), and Au(III) complexes, but in Pt(IV) and Pd(II) complexes, the amlodipine besylate coordinates via NH₂ and OH (besylate) groups. An octahedral geometry is proposed for all complexes except for the Cd(II), Pt(IV), and Pd(II) complexes. The amlodipine besylate free ligand and the transition and non-transition complexes showed antibacterial activity towards some Gram-positive and Gram-negative bacteria and the fungi (Aspergillus flavus and Candida albicans).     

Construction of a thermoanalyzer for DTA-TD-TMAG-T measurements on metals up to 1100 °C

A thermoanalyzer is described for the simultaneous testing of metals and alloys by three methods: differential thermal analysis (DTA), thermal dilatometry (TD) and thermomagnetometry (TMAG). One reference specimen is used as a standard for each of the above kinds of analysis. Measurements can be performed in vacuum or in a static or dynamic atmosphere of gases at any pressure between normal and 5× 10^–5 Torr. The temperature of the sample can be changed linearly in the range 20–1100 °C. DTA and TD are performed classically, whereas TMAG is based on the temperature and magnetic field-dependences of the reversible magnetic susceptibility of the sample. Some analysis results are presented.

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Zusammenfassung Es wird ein Thermoanalysator zur simultanen Untersuchung von Metallen und Legierungen durch drei Methoden beschrieben: Differentialthermoanalyse (DTA), Thermodilatometrie (TD) und Thermomagnetometrie (TMAG). Für alle drei Verfahren wurde die gleiche Referenzsubstanz als Standard benutzt. Messungen können im Vakuum oder is statischer bzw. bewegter Atmosphäre von Gasen beliebigen Druckes zwischen Normaldruck und 5·10^–5 Torr durchgeführt werden. Die Temperatur der Probe kann zwischen 20 und 1100 °C linear variiert werden. Während DTA und TG die herkömmlichen Verfahren zu Grunde liegen, basiert TMAG auf der Temperatur- und Magnetfeldabhängigkeit der reversiblen magnetischen Suszeptibilität der Probe. Einige Analysenergebnisse wurden dargestellt.

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: (), () (). . , 5·10^–5 . 20–1100°. , . .

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Presented at the 4th European Symposium on Thermal Analysis and Calorimetry, Jena, GDR, August 1987.     

Atomic emission and atomic absorption spectrometric analysis of high-purity powders for the production of ceramics

Summary Direct analysis methods and multistage combined analytical procedures for the determination of impurities at the g/g level and the upper ng/g level in high-purity powders of Al₂O₃, AlN, Si₃N₄ and SiC are described. Results obtained with a novel direct slurry-atomization technique using a Babington nebulizer and inductively coupled plasma optical emission spectrometry (ICP-OES) are presented. A comparison of analysis results of combined analytical procedures including wet chemical decomposition and determinations with graphite furnace atomic absorption spectrometry (ETAAS) or ICP-OES with those of slurry-atomization ICP-OES show the capabilities of this technique for routine analysis in production control. Detection limits for Al, B, Ca, Co, Cu, Fe, Mg, Mn, Si, Ti, W, V, and Zn in the matrices mentioned are between 0.03 and 2.5 g/g. For elemental concentrations 10 g/g relative standard deviations of the measurements are generally below 10%. The technique is shown to be a powerful tool for trace determinations in powder samples. This is shown by its use for analysis of a series of the ceramic powders mentioned and comparative results of other direct techniques such as total reflection X-ray fluorescence spectrometry and instrumental neutron activation analysis.

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OES und AAS von hochreinen Pulvern für die Keramikherstellung

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Herrn Prof. Dr. G. Tölg zum 60. Geburtstag von seinen Mitarbeitern gewidmet