FT-IR,ESI and EPR studies of a Dy(III) Schiff base podand complex

IR spectroscopic, electrospray ionization mass spectrometry, structure and magnetic properties of a dysprosium(III) macroacyclic tripodal Schiff base tris((2-(5-chlorosalicylideno)amino)ethyl)amine (tren-5Clsal) complex are reported. The positions of ν(CN) stretching bonds indicate that the azomethine group nitrogen is coordinated to the rare earth ion. Two main spectral components are observed in the low magnetic field region (<300 mT) in the EPR spectra, independently of temperature. These components are attributed to the Dy³⁺ ion with an effective spin of S = 1/2. The magnetic anisotropy between 3 and 23 K is practically constant as evidenced only by a marginal change of the spread of g-factors. The g_y-factor increases strongly with an increase in temperature above 23 K, giving rise to a very high magnetic anisotropy of the complex. Such behavior of the magnetic anisotropy at a higher temperature could be an effect of the existence of an excited doublet. A very small value of the Curie–Weiss constant and the lack of any meaningful thermal changes of linewidths indicates the absence of any significant interactions between Dy(III) complexes below 20 K. The temperature dependence of the total integrated intensity above 20 K indicates the existence of an excited doublet, occurring about 33(1) K above the ground state.     

Silicone‐urethane membranes for lithium batteries. Part 1. Moisture‐cured poly(siloxane‐urethane‐urea) elastomers containing polyethylene oxide (PEO) segments – synthesis and characterization as potential membrane materials

Poly(siloxane‐urethane‐urea) elastomers containing both polysiloxane and polyethylene oxide (PEO) segments in the polymer chain were obtained by moisture‐curing of NCO‐terminated poly(siloxane‐urethane) prepolymers synthesized from isophorone diisocyanate and mixtures of polyoxyethylene diols and polysiloxane diols with various molecular weights. Mechanical properties of the moisture‐cured films and their swelling ability in solvent mixtures commonly used in lithium batteries were investigated, and it was found that they were greatly influenced by PEO content in the polymer. PEO content in the polymer was also found to affect very much the electric conductivity of the films after immersion in lithium salt solution in ethylene carbonate–dimethyl carbonate solvent mixture. At high contents of PEO in the polymer chain specific conductivities of the films in a range of 10^?3, Scm^?1 could be achieved at room temperature. Based on the results of Scanning Electron Microscopy with X‐ray Analysis (SEM/EDS) investigations and wide‐angle X‐ray scattering and small‐angle X‐ray scattering studies, it could be anticipated that the reason for good conductivity of the films might be their specific supramolecular structure that potentially facilitated lithium ion mobility. Copyright © 2015 John Wiley & Sons, Ltd.     

Application of very small force measurements in monitoring the response of sunflower to weak blue light

A diaheliotropic response of sunflower, Helianthus annuus, following a short pulse of low intensity blue light to a small area of leaf surface was examined with the application of the very low-force-measurements technique (the order of magnitude of 10(-5) N). One leaf from a pair was illuminated with a low intensity blue-light-pulse and the force was recorded, generated by the stem of the plant tending to bend. A very low phototropic effect in response to blue light alone was observed which could be considerably enhanced by the application of background illumination with red light. Microelectrode measurements of the membrane potential of the mesophyll cells of the sunflower leaf showed hyperpolarization in response to a blue light pulse, observed very clearly under application of the red light background illumination. The hyperpolarization of the membrane potential was accompanied by acidification of extracellular compartments as monitored with a miniature pH-sensitive electrode, placed in the epidermis of the stem. The relatively short lag period between the hyperpolarization of the membrane potential and the decrease in pH suggests that the hyperpolarization is a direct effect of the blue light-induced proton extrusion. The acidification correlates with the light response, which suggests that acidification-induced stem wall loosening is responsible for the blue light-induced bending. The examined mechanisms are discussed in terms of sun tracking by a sunflower.     

Pressurized liquid extraction of coumarins from fruits of Heracleum leskowii with application of solvents with different polarity under increasing temperature

Coumarins are nowadays an important group of organic compounds from natural sources that are useful in a number of fields. Because they possess different pharmacological properties, finding the proper extraction conditions for their separation from plant matrices is a very important step. In this report Pressurized Liquid Extraction (PLE) under different temperature conditions and with different types of extraction solvents were tested. As a matrix, fruits of Heracleum leskowii have been used. A simple reverse phase high-performance liquid chromatographic method (RP-HPLC) coupled with a photodiode array detector (DAD) has been developed for separation and quantitative analysis of the main coumarins. Umbelliferone, xanthotoxin, angelicin, isopimpinellin, bergapten, imperatorin and isoimperatorin were investigated. Bergapten and imperatorin were dominant in almost all extracts in the range of 9.92 ± 0.02-20.93 ± 0.06 and 12.19 ± 0.98-19.07 ± 0.03 mg/100 g, respectively. Dichloromethane and methanol were chosen as the most proper suitable solvents for extraction of coumarins. By increasing the temperature the amount of extracted coumarins increases in petroleum ether and dichloromethane extracts.     

Application of Internal Standard for Micro Extraction– Spectrophotometric Determination of Bismuth in Pharmaceutical Formulations

 A micro extraction – spectrophotometric procedure is developed for the determination of bismuth in pharmaceutical formulations. The procedure is based on the extraction of tetraiodobismuthate(III) ion paired with benzyltributylammonium cation into chloroform. The application of Nile Blue as internal standard (IS) enabled good analytical performance for micro-scale analysis. The ratio between the absorbances measured at 491 nm (bismuth complex) and at 632 nm (IS) was taken as the analytical signal. The procedure was carried out in Eppendorf tubes, lowering significantly the use of reagents and the volume of organic solvent. In the calibration range up to 60 mgċl⁻¹, the linear regression coefficient was 0.9999, the CV for 15 mgċl⁻¹ and for 50 mgċl⁻¹ Bi were 1.6% and 0.7% respectively. The results obtained in the analysis of pharmaceutical formulations were in good agreement with the results of EDTA titration method. Received November 25, 1999. Revision February 14, 2000.     

Use of Two-Dimensional TLC to Identify Phenolic Acids in the Foliage and Fruit of Peucedanum tauricum Bieb.

JPC – Journal of Planar Chromatography – Modern TLC - Two-dimensional planar chromatography (2D TLC) on cellulose layers, solid phase extraction (SPE), and reversed-phase...     

Random iterations, fixed points and invariant CRF-horospheres in complex Banach spaces

For holomorphic noncontractive maps on (not necessarily bounded) domains in complex Banach spaces, we establish the conditions guaranteeing locally uniform convergence of random iterations and study the existence of fixed points and boundary behaviour of iterations. In particular, we show that the problem, concerning the existence of the horospheres determined by Carathéodory-Reiffen-Finsler pseudometrics defined on unbounded domains, has the solution and we prove new results of type of Julia's lemma and Wolff's theorem.