Synthesis and spectroscopic studies of mixed-ligand and polymeric dinuclear transition metal complexes with bis-acylhydrazone tetradentate ligands and 1,10-phenanthroline

Two types of dinuclear copper(II) and nickel(II) complexes with two tetradentate N2O2 donor ligands 1,4-bis(1-anthranoylhydrazonoethyl)benzene (L1), 1,4-bis(1-salicyloylhydrazonoethyl)benzene (L2) and N,N'-bidentate heterocyclic base [1,10-phenonthroline (phen)] have been synthesized and characterized by elemental analysis, infrared spectra, UV-vis electronic absorption spectra and magnetic susceptibility measurements. The reaction of metal(II) acetates with the solution containing ligand and 1,10-phenonthroline in methanol gives mixed-ligand dinuclear metal(II) complexes with general formula [M2L(phen)2]Cl2 (L=L1 or L2), whereas, the ligands react with metal(II) acetates to form polymeric dinuclear complexes with general formula [(M2L2)n] (L=L1 or L2). In the complexes, the ligands act as dianionic tetradentate and coordination takes place in the enol tautomeric form with the enolic oxygen and azomethine nitrogen atoms while the phenolic hydroxyl and amino groups of aroylhydrazone moiety do not participate in coordination. The effect of varying pH and solvent on the absorption behavior of both ligands and complexes has been investigated.     

Exact solution of Schrödinger equation for Pseudoharmonic potential

Exact solution of Schr?dinger equation for the pseudoharmonic potential is obtained for an arbitrary angular momentum. The energy eigenvalues and corresponding eigenfunctions are calculated by Nikiforov–Uvarov method. Wavefunctions are expressed in terms of Jacobi polynomials. The energy eigenvalues are calculated numerically for some values of ℓ and n with n ≤ 5 for some diatomic molecules.      

Polyurethane elastomers with hydrolytic and thermooxidative stability. I. Polyurethanes with N-alkylated polyamide soft blocks

Segmented polyurethanes with N-alkylated amides as soft blocks as prepared. Comparisons are made with both a poly(ester urethane) and a poly(ether urethane) with the same hard block; the poly(amide urethane) is more hydrolytically stable than the polyester containing material and demonstrates greater thermooxidative stability than that with the polyether moiety. The aliphatic poly(amide urethane)s remain transparent upon exposure to uv light.     

Synthesis of Some Novel Norbornene‐Fused Pyridazines as Potent Inhibitors of Carbonic Anhydrase and Acetylcholinesterase

The reaction of benzocyclic norbornene derivatives with tetrazines provided the 1,3‐dihydropyridazine derivatives as a single product. The dihydropyridazine derivatives have been dehydrogenated with phenyliodine bis(trifluoroacetate) to yield the corresponding pyridazines in a high yield. Two stable diazines, primary product of corresponding 1,4‐dihydropyridazine, were also isolated. Structures were then determined by ¹H‐NMR, and ¹³C‐NMR beside to elemental analyses. The novel pyridazine derivatives ( 8 , 9 ) efficiently inhibited the cytosolic human carbonic anhydrase isoenzymes I and II (hCA I and II). In addition, these novel pyridazine derivatives ( 8 , 9 ) were evaluated for their in vitro acetylcholinesterase inhibitory activity. Ligand–receptor interactions are tested using molecular docking simulations. Obtained docking scores are in good agreement with in vitro results.     

Der Einfluß der Auffängertemperatur auf die Ausbeute beimβ-Rückstoß von ThB

Zeitschrift für Physik A Hadrons and nuclei - Durch neue Versuche über die Ausbeute beim β-Rückstoß von Th B wird gezeigt, daß ähnlich wie bei den...     

A thermogravimetric method for the measurement of CO/CO2 ratio at the surface of carbon during combustion

This work presents a new method of measuring the CO/CO₂ ratio at the surface of carbon particles during combustion. This thermogravimetric method deduces the ratio of CO to CO₂ by comparing the rate of consumption of carbon with the rate of oxidation of an external reference material with fast oxidation kinetics, in this case Cu. The method is useful when combustion is controlled by external mass transfer, commonly encountered in large-scale processes. The viability of this method has been demonstrated experimentally with graphite and a lignite char. It was found that in an atmosphere of ～ 1% O₂, the graphite produced CO₂ between 700 and 900 °C whilst the lignite char produced a mixture of CO and CO₂ between 700 and 800 °C with the proportion of CO increasing with temperature, and above 850 °C, only CO was produced. It was also found that for this particular lignite char, the ratio of CO/CO₂ increased with decreasing pO₂ in the environment.     

The Stereostructure of Porphyra‐334: An Experimental and Calculational NMR Investigation. Evidence for an Efficient ‘Proton Sponge’

The mycosporine‐like amino acid (MAA) porphyra‐334 ( 1 ) is subjected to extensive ¹H‐ and ¹³C‐NMR analysis as well as to density‐functional‐theory (DFT) calculations. All ¹H‐ and ¹³C‐NMR signals of 1 are assigned, as well as the resonances of prochiral proton pairs. This is achieved by 500‐MHz standard COSY, HMQC, and HMBC experiments, as well as by one‐dimensional (DPFGSE‐NOE) and two‐dimensional (NOESY) NOE experiments. Diffusion measurements (DOSY) confirm that 1 is monomeric in D₂O solution. DFT Calculations yield ¹³C‐NMR chemical shifts which are in good agreement for species 6 which is the imino N‐protonated form of 1 . An exceptionally high proton affinity of 265.7 kcal/mol is calculated for 1 , indicating that 1 may behave as a very powerful ‘proton sponge’ of comparable strength as synthetic systems studied so far. Predictions of ¹³C‐NMR chemical shifts by the ‘NMRPredict’ software are in agreement with the DFT data. The absolute configuration at the ring stereogenic center of 1 is concluded to be (S) from NOE data as well as from similarities with the absolute configuration (S) found in mycosporine‐glycine 16 . This supports the assumption that 1 is biochemically derived from 3,3‐O‐didehydroquinic acid ( 17 ). The data obtained question the results recently published by a different research group claiming that the configuration at the imino moiety of 1 is (Z), rather than (E) as established by the here presented study.     

Propolis-Based Nanofiber Patches to Repair Corneal Microbial Keratitis

In this research, polyvinyl-alcohol (PVA)/gelatin (GEL)/propolis (Ps) biocompatible nanofiber patches were fabricated via electrospinning technique. The controlled release of Propolis, surface wettability behaviors, antimicrobial activities against the S. aureus and P. aeruginosa, and biocompatibility properties with the mesenchymal stem cells (MSCs) were investigated in detail. By adding 0.5, 1, and 3 wt.% GEL into the 13 wt.% PVA, the morphological and mechanical results suggested that 13 wt.% PVA/0.5 wt.% GEL patch can be an ideal matrix for 3 and 5 wt.% propolis addition. Morphological results revealed that the diameters of the electrospun nanofiber patches were increased with GEL (from 290 nm to 400 nm) and Ps addition and crosslinking process cause the formation of thicker nanofibers. The tensile strength and elongation at break enhancement were also determined for 13 wt.% PVA/0.5 wt.% GEL/3 wt.% Ps patch. Propolis was released quickly in the first hour and arrived at a plateau. Cell culture and contact angle results confirmed that the 3 wt.% addition of propolis reinforced mesenchymal stem cell proliferation and wettability properties of the patches. The antimicrobial activity demonstrated that propolis loaded patches had antibacterial activity against the S. aureus, but for P. aeruginosa, more studies should be performed.     

One-step in-syringe dispersive liquid–liquid microextraction and GC-FID determination of trace amounts of di(2-ethylhexyl) phthalate and its metabolite in human urine samples

Di(2-ethylhexyl) phthalate (DEHP) is used as plasticizer in polyvinylchloride (PVC) plastics. Its metabolites and the parent phthalates are considered toxic. As the DEHP plasticizers are not chemically bound to PVC, they can migrate, evaporate or be leached into indoor air and atmosphere, foodstuff, and other materials. We have reported a novel, easy and available analytical method for the determination of DEHP and its metabolite, mono(2-ethylhexyl) phthalate (MEHP) in human urine samples by the in-syringe dispersive liquid–liquid microextraction method coupled with gas chromatography with flame ionization detector. The limits of detection and precision (RSD) were 2.5 μg/L and 1.4% for DEHP and 1.1 μg/L and 3.0% for MEHP, respectively. This method could be utilized for routine monitoring of the trace DEHP and MEHP in urine of human exposure to plasticizers.     

Electron paramagnetic resonance characterization of gamma irradiation damage centers in powder of L-(+)-tartaric acid,N-acetyl-L-alanine and 1-methyl-L-histidine

The electron paramagnetic resonance (EPR) of γ-irradiated powders of l-(+)-tartaric acid, N-acetyl-l-alanine and 1-methyl-l-histidine were investigated at room temperature. Radiation damage centers are attributed to HOOCCH(OH)?(OH)COOH, CH₃?HCOOH and ?CH₂?HCOOH radicals. The spectra were computer-simulated. Hyperfine structure constants and g-values were determined for these three radicals. The unirradiated samples showed no EPR signal. Some spectroscopic properties and suggestions concerning the possible structure of the radicals are discussed in this paper.