Nucleophilicity of N-propargylanilines in the coordination to zinc tetraphenylporphyrin in chloroform

Thermodynamic parameters (ΔG ⁰ and ΔS ⁰) of the isoenthalpic (except for 4-halo derivatives) coordination of (tetraphenylporphyrinato)zinc(II) with anilines in chloroform at 273–313 K linearly correlate with the shift of their electronic absorption maxima in the reaction with anilines, as well as with the logarithms of the stability constants of the complexes, pK _a values of the ligands in water, and substituent constants σ⁺. The 2: 1 complex of (tetraphenylporphyrinato)zinc(II) with p-phenylenediamine was characterized by the X-ray diffraction data     

Calculation of autocorrelation functions for electronic spectra

The autocorrelation function C(t) associated with the vibrational motion in the A²II_u state of N₂⁺ is calculated by three different methods. The classical method is based on classical trajectory calculations and provides good results except for secondary maxima appearing in the experimental autocorrelation function and resulting from interference effects. In the semiclassical method, the wavefunction is expanded in a basis of frozen gaussian functions. The secondary maxima are reproduced and the result is quite satisfactory. The superposition procedure consists in an expansion of the wavefunction in the eigenfunctions of the A state of N₂⁺ and leads to a very simple formula for the autocorrelation function C(t). The secondary maxima are accounted for and the calculated function agrees very well with experimental results.     

Synthesis and spectroscopic properties of new 5-oxazolone derivatives containing an N-phenyl-aza-15-crown-5 moiety

Novel 5-oxazolone derivatives containing an N-phenyl-aza-15-crown-5 moiety were synthesized for the first time. The structures of the new derivatives were confirmed by ¹H NMR, ¹³C NMR and FT-IR. In addition, evaluation of the visible absorption and emission properties of the structures were carried out in eight different solvents. The products show intense visible absorption maxima in the range 467-524 nm, and fluoresced strongly, with emission maxima from 496 to 689 nm in all the solvents tested.     

Synthesis and properties of magnetic semiconductor InSb〈Mn,Cd〉

Polycrystalline indium antimonide samples codoped with manganese (0.8–1 at %) and cadmium (3.9 at %) are prepared by quenching from melt. Despite the high contents of these dopants, only InSb maxima are observed in X-ray diffraction patterns of these samples. As probed by magnetic studies, the samples are ferrimagnets having Curie points of about 577 K and room-temperature specific magnetizations of σ ≈ 0.5 G cm³/g (H = 6 kOe). We suggest that the magnetic properties of the samples are dictated by InSb〈Mn,Cd〉 microinclusions, which are located in grain boundaries and dislocations.     

Notiz zur photometrischen Bestimmung von Triphenylmethanol über das Triphenylmethylkation

The absorption spectrum of the triphenylmethyl cation, made from triphenylmethanol and conc, sulphuric acid, has been measured and compared with the literature. There are absorption maxima at 434 and 409 nm. The molar extinction coefficient for λ=436 nm has been determined to be ? _M =38.88×10³ cm²/mMol. Ether, water, and benzophenone do not interfere.     

Alignment of atomic autoionizing states created by slow Li++Ne collisions

Ejected-electron spectra have been measured in collisions of Ne-atoms with Li⁺-ions, whose impact energy has been ranged from 0.4 to 7.0 keV. The ion impact-energy dependence has been investigated on the angular-differential cross-section of the ejected electrons from the aligned autoionizing state Ne** 2p ⁴3s ^{2 1} D. In the highest energies studied, cross section maxima have been found at both forward and backward angles with respect to the Li⁺-ion beam direction, whereas the cross sections are maximized at around right angles below intermediate energies. The data were analyzed semi-quantitatively, and the alignment of the autoionizing state was recognized to be characterized by a representative scattering angle of the Li⁺-ions.     

Spectrofluorometric determination of certain quinolone antibacterials using metal chelation

Simple, rapid, reliable, and sensitive spectrofluorometric methods were developed for the determination of eight quinolone antibacterials namely ciprofloxacin, norfloxacin, lomefloxacin, difloxacin, amifloxacin, pefloxacin, ofloxacin, and nalidixic acid. The methods depend on the chelation of each of the studied drugs with zirconium, molybdenum, vanadium or tungsten to produce fluorescent chelates. Different factors affecting the relative fluorescence intensity of the resulting chelates were studied and optimised. At the optimum reaction conditions, the drug-metal chelates showed excitation maxima ranging from 274 to 295 nm and emission maxima ranging from 409 to 495 nm. The chelates were found to be stable at room temperature for 2 days and show good stability upon increasing temperature to 50 °C for about 1 h. Rectilinear calibration graphs were obtained in the range of 10-60 ng ml⁻¹ for each of the investigated drugs and the limits of detection and quantitation ranged from 1.214 to 2.046 and from 4.047 to 6.819 ng ml⁻¹, respectively. The molar ratios of the formed chelates were determined by Job's method and their association constants were also calculated. The developed methods were applied successfully for the determination of the studied drugs in their pharmaceutical dosage forms with a good precision and accuracy compared to official and reported methods as revealed by t- and F-tests. They were also applied for the determination of studied drugs in spiked urine and plasma samples.     

Structural characterization, magnetic behavior and high-resolution EELS study of new perovskites Sr2Ru2−xCoxO6−δ (0.5?x?1.5)

New oxides of general formula Sr₂Ru_2−xCo_xO_6−δ (0.5?x?1.5) have been synthesized as polycrystalline materials and characterized structurally by X-ray diffraction. For 0.5?x<0.67 the orthorhombic, Pnma, perovskite structure of the end member, SrRuO₃, is found. At x=0.67 a phase separation into an Ru-rich Pnma phase and a Co-rich I2/c phase occurs. The I2/c form is also found for x=1.0 but another orthorhombic phase, Imma, obtains for x=1.33 and 1.5. Reductive weight losses indicate negligible oxygen non-stoichiometry, i.e., δ∼0, for all compositions even those rich in Co. High-resolution electron energy loss spectroscopy (EELS) indicates that cobalt is high-spin Co³⁺ or high-spin Co⁴⁺ for all x. Appropriate combinations of Ru⁴⁺, Ru⁵⁺, HS Co³⁺ and HS Co⁴⁺ are proposed for each x which are consistent with the observed Ru(Co)-O distances. Significant amounts of Co⁴⁺ must be present for large x values to explain the short observed distances. Broad maxima in the d.c. susceptibilities are found between 78 and 97 K with increasing x, along with zero-field-cooled (ZFC) and field-cooled (FC) divergences suggesting glassy magnetic freezing. A feature near 155 K for all samples indicates a residual amount of ferromagnetic SrRuO₃ not detected by X-ray diffraction.     

One-dimensional J-aggregates: Dependence of the properties of the exciton band on the model of the intermolecular coupling

The spectral properties of one-dimensional thiacarbocyanine dye aggregates were simulated by the combination of exciton interaction with a diagonal energetic disorder. Contrary to previous models incorporating disorder, the exciton interaction was calculated using the transition densities obtained form PPP-wave functions and interactions between all molecules were considered. The effects of the aggregate size, non-nearest neighbor interactions, diagonal disorder and to some extent exciton phonon coupling on the spectral position of the maxima, the FWHM of the spectra and the superradiance are investigated for H- and J-aggregates at 298 and 20 K. At 298 K the experimental properties of H-aggregates and J-aggregates of 3,3^′-disulfopropyl-5,5^′-dichloro-carbocyanine with 1 molecule per unit cell are compared to the simulations.     

Size effects in the CO-oxidation over supported Pd particles

Low pressure CO oxidation was studied over small supported Pd particles by means of static secondary ion mass spectrometry (SSIMS). The SSIMS spectra of adsorbed layers on Pd particles with diameters below ～7nm contained, besides other species, Pd _n X⁺ ions (X=C, O, CO;n=1–3). In experiments with Pd films, Pd _n C⁺ species were much less abundant or even absent from the mass spectra. We conclude that CO decomposed in appreciable amounts only on Pd particles. No significant influence of the support material (mica, MgO,α-Al₂O₃) was seen and posthumous TEM analysis revealed well defined particle morphologies with largely (111) and (100) facets. At total pressures below 10^?4 Pa, the relative carbidic intensities Pd _n C⁺/Pd _n ⁺ , which were taken as proportional to the carbon surface concentrations, first increased with increasing temperatures and then decreased after they passed a maximum at T=400–440 K. The smaller the particle size, the more intense were the maxima. For T ?440 K, carbon was removed from the surface via reaction with oxygen. Strong hysteresis effects in the C_ad and CO_ad concentrations occurred during temperature variation measurements. The Pd _n C⁺/Pd _n ⁺ ratios displayed maxima during heating but not during cooling. While the Pd _n CO⁺/Pd _n ⁺ ratios were always high at 300 K and always low at T>550 K, they were more intense in the medium temperature range when subjecting the samples to heating. These hysteresis effects are discussed in terms of asymmetric adsorption and reaction behaviour of CO/O₂ mixtures, involving inhibition of CO₂ formation by adsorbed carbon and carbon monoxide.     

Solvent extraction and spectrophotometric determination of iron(II) with 2,2′-dipyridyl-2-furancarbothiohydrazone

2,2′-Dipyridyl-2-furancarbothiohydrazone (DPFTH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) can be quantitatively extracted with DPFTH in benzene from aqueous solution buffered to 3.0–8.0. The extracted species has absorption maxima at 440, 477, and 738 nm and obeyed Beer's law over the range 0–40 μg of iron in 10 ml at 738 nm. The molar absorptivity at this wave length is 1.17 × 10⁴ liters mole^?1 cm^?1. The proposed method is relatively selective for iron(II) and is satisfactorily applied to the determination of the total iron in natural waters. The proton dissociation constants of the ligand determined spectrophotometrically were pK_a1 = 2.88 and pK_a1 = 6.70 at 25 °C and μ = 0.1.     

Quantum effects in molecular dynamics and fracture kinetics of polymers

Molecular dynamics in crystallites of a number of polymers, such as polyethylene, nylon-6, poly-(vinyl alcohol), was studied at temperatures ranging from 4.2 to 400 K using the X-ray diffraction technique. Thermal expansion of the lattice was measured by the temperature-induced displacements of diffraction maxima. The thermal expansion coefficient was found to grow from 0 to ∼10⁻⁴ K⁻¹, this fact being the evidence of the quantum statistics in the vibrational dynamics of straightened molecules over the whole temperature range. Characteristic temperatures of vibrations were estimated. The kinetics of fracture was studied using highly - oriented nylon-6 and KEVLAR-49 fibers. Tensile strength (σ_r) was measured as a function of loading rate σ and temperature (T) in the range from 4.2 to 400–600 K. The observed specific features of the σ_r(σ) and σ_r(T) curves at low temperatures correspond to tunnel scission of stressed chain molecules.     

Relations between mean amplitudes of vibration and corresponding internuclear distances: I. bonded and nonbonded carbon-carbon distances

Mean amplitudes of vibration (u) for bonded and non-bonded CC distances from gas electron diffraction were treated statistically. The following empirical relation was established on the basis of 71 measurements u(CC) = 0.013837 + 0.023398r-0.000147r² where r is the internuclear distance in the range 1.217 ? r? 5.618 (r and u are both in Å). The experimental data come mainly from electron diffraction laboratories in U.S.A., Norway, Japan and England.     

Spectrophotometric determination of aluminium and gallium with pyrogallol red and cetyltrimethylammonium ions

Spectrophotometric methods are described for the determination of microgram amounts of aluminium and gallium based on the formation of a ternary complex between the metal, pyrogallol red, and cetyltrimethylammonium bromide. The complexes have absorbance maxima at 610 and 615 nm, respectively, with molar absorptivities of 4.8 × 10⁴(Al)and 1.0 × 10⁵ liter mol^?1 cm^?1 (Ga). Numerous metals interfere. Gallium can be separated by extraction of gallium from 7 M hydrochloric acid with di-isopropyl ether. However, aluminium can be separated by extraction of interfering ions with cupferron.     

Structural and magnetic study of RFe0.5V0.5O3 (R=Y, Eu, Nd, La) perovskite compounds

B-site disordered RFe_0.5V_0.5O₃ compounds, with R=La, Nd, Eu and Y, have been prepared by solid-state reaction technique and their structures and magnetic properties have been investigated through X-ray powder diffraction, time-of-flight neutron powder diffraction and magnetization measurements at temperatures ranging from 5 to 700 K. The four compounds can be described as distorted perovskites with space group symmetry Pbnm and a⁺b⁻b⁻ tilt system. The studied compounds also show antiferromagnetic ordering with Neel temperatures of 299, 304, 304, and 335 K respectively. The magnetic structures of R=La, Nd and Y compounds were determined from the neutron powder diffraction as G_z with observed magnetic moments of 2.55, 2.54 and 2.69μ_B at 30, 40 and 40 K, respectively.     

Radiothermoluminescence of tetiamethylene sulfoxide

Radiothermoluminescence (RTL) and ESR spectra of tetramethylene sulfoxide (TMSO) irradiated by X-ray and⁶⁰Co γ-ray radiation have been studied at 77 K. The temperatures of RTL maxima were correlated with the changes in color of specimens and the shape of the ESR spectral lines. The temperatures at which maxima or inflections are observed (depending on the kind of irradiation, dose, and introduced additives) were determined: 90, 115, 125, 133, 145, and 155 K. A signal of the TMSO radical cation was observed in the ESR spectrum (a singfet with g = 2.008±0.001 and δH = 12 Oc); it completely disappeared after the cessation of luminescence at the maximum at 133 K. An analogous result is achieved by illumination of the specimen with maximum effect in the yellow-green region of the spectrum. Activation of RTL by the UO₂ ²⁺ and Tb³⁺ ions was studied. Their thermal deactivation was correlated with molecular mobility manifested in RTL.     

Thermal analysis of a white calcium bentonite

A white calcium bentonite (CaB) taken from Çaml?dere (Ankara, Turkey) region was heated at various temperatures between 100 and 1100 °C for 2 h. The mineralogy of the CaB was determined as calcium smectite (CaS), metahalloysite (MH), opal-A (OA), opal-CT (OCT), quartz (Q), feldspar (F), and calcite (C) using the X-ray diffraction patterns of the natural CaB and its heated samples. Besides the XRD patterns, the thermogravimetry, differential thermal analysis, and low-temperature nitrogen adsorption (N₂-AD) data show that the CaS lose adsorbed and hydration water up to 300 °C, dehydroxylation takes place between 300 and 750 °C, and then the 2:1 layer structure completely collapses above 900 °C. The activation energies for the dehydration and dehydroxylation were calculated as 7636 and 48838 J mol^?1, respectively, from the TG data using Coats and Redfern method. The specific surface area (S) and specific micro–mesopore volume (V) obtained from N₂-AD data were 44 m² g^?1 and 0.100 cm³ g^?1 for the natural CaB. S and V reach their maxima of 105 m² g^?1 and 0.155 cm³ g^?1, respectively, at 300 °C, remain approximately constant as the temperature increases up to 700 °C and then decrease almost in parallel with each other, reaching their minima at 900 °C. This indicates that the S and V values increase gradually during dehydration and dehydroxylation of the CaS.     

Spectrophotometric determination of vanadium with n-benzoyl-o-tolylhydroxylamine

N-Benzoyl-o-tolylhydroxylamine is shown to provide a virtually specific reagent for the spectrophotometric determination of vanadium. The reddish-violet complex formed with the reagent in 4–8 N hydrochloric acid after extraction with chloroform shows absorption maxima at 510 mm, and obeyes Beer's law from 0.5 to 10 μg with an optimum range of 2–10 μg; the percent relative error is 2.7. The sensitivity is 0.0108 μg V/cm². The complex contains the metal and the reagent in a ratio of 1:2 and the dissociation constant is of the order of 10^-9.     

Synthesis,self-assembly and optical properties of novel fluorescent alkoxy-substituted fluoroaryl 1, 3, 4-oxadiazole organogelator

Aromatic nucleophilic substitution (S_NAr) reactions have been known to be regioselective to the para position on a variety of substituted perfluorobenzenes. In the current study, a series of fluoroaryl 1, 3, 4-oxadiazole derivatives substituted with different para terminal ethers were synthesized using S_NAr chemistry to afford fluorescent and thermally reversible low molecular weight organogelators (LMWOs). S_NAr was used to synthesize these highly fluorinated organogelators in high purity and good yields starting from pentafluorobenzoic acid and 4′-hydroxy-4-biphenylcarbonitrile. These fluorinated 1, 3, 4-oxadiazole derivatives were characterized by elemental analysis, FTIR, and ¹H, ¹³C, and ¹⁹F NMR spectroscopy. The photophysical properties of those organogelators were described. Both UV–visible absorption and fluorescence spectral profiles displayed a solvatochromic and solvatofluorochromic properties. The absorption maxima for the developed organogelators were monitored in the range of 260–289 nm, whereas the emission maxima were monitored in the range of 278–305 nm. The best gelation properties were monitored for the hexyloxy-substituted 2-(biphenylyl)-5-(perflurophenyl)-1, 3, 4-oxadiazole gelator in different solvents with critical gel concentrations in the range of 1.86–5.07 mM. The self-assembly process was monitored to occur via van der Waals forces and π-π stacks to result in gelation of solvents. Scanning electron microscope (SEM) demonstrated nanofiber-like structures (350–550 nm). The thermal stability of the hexyloxy-substituted organogel was monitored at 48 °C. Both cytotoxicity and antimicrobial activity of the produced fluoroaryl 1, 3, 4-oxadiazole derivatives were explored to verify their potential use for biomedical applications, such as drug delivery and bioimaging.     

Photocatalytic Degradation of Palm Oil Mill Effluent (POME) Waste Using BiVO4 Based Catalysts

Disposal of palm oil mill effluent (POME), which is highly polluting from the palm oil industry, needs to be handled properly to minimize the harmful impact on the surrounding environment. Photocatalytic technology is one of the advanced technologies that can be developed due to its low operating costs, as well as being sustainable, renewable, and environmentally friendly. This paper reports on the photocatalytic degradation of palm oil mill effluent (POME) using a BiVO₄ photocatalyst under UV-visible light irradiation. BiVO₄ photocatalysts were synthesized via sol-gel method and their physical and chemical properties were characterized using several characterization tools including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), surface area analysis using the BET method, Raman spectroscopy, electron paramagnetic resonance (EPR), and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). The effect of calcination temperature on the properties and photocatalytic performance for POME degradation using BiVO₄ photocatalyst was also studied. XRD characterization data show a phase transformation of BiVO₄ from tetragonal to monoclinic phase at a temperature of 450 °C (BV-450). The defect site comprising of vanadium vacancy (V_v) was generated through calcination under air and maxima at the BV-450 sample and proposed as the origin of the highest reaction rate constant (k) of photocatalytic POME removal among various calcination temperature treatments with a k value of 1.04 × 10⁻³ min⁻¹. These findings provide design guidelines to develop efficient BiVO₄-based photocatalyst through defect engineering for potential scalable photocatalytic organic pollutant degradation.