Equilibrium studies on some heteroligand hydroxo complexes of lanthanons with iminodiacetic acid and citraconic or maleic acid

Mixed-ligand ternary complexes of La(III), Pr(III), Nd(III), Gd(III), and Dy(III) with iminodiacetic acid (IMDA) and citraconic (CCA) or maleic acid (MIA), have been studiedpH-metrically. Their formation takes place through the stepwise addition of the secondary ligand (IMDA) to the initially formed 1:1, Ln(III)—CCA/MIA binary species. The resulting ternary complexes undergo hydrolysis to form their hydroxo derivatives simultaneously. The stability constants of the hydroxo species are calculated for constant temperature (27 ± 1°C) and ionic strength (I=0.1M KNO₃). The relative order of stability is: La(III)

Gleichgewichtsuntersuchungen an einigen Heteroliganden-Hydroxo-Komplexen von Lanthanid-Ionen mit Iminodiessigsäure und Citracon- oder Maleinsäure

Zusammenfassung Es wurden ternäre Komplexe von La(III), Pr(III), Nd(III), Gd(III) und Dy(III) mit gemischten Liganden [Iminodiessigsäure (IMDA) und Citraconsäure (CCA) oder Maleinsäure (MIA)] mittelspH-metrischer Methoden untersucht. Diese Komplexe werden über die stufenweise Addition des Sekundärliganden (IMDA) zu den primär gebildeten 1:1 Ln(III)—CCA/MIA Spezies gebildet. Zugleich erleiden die resultierenden ternären Komplexe Hydrolyse und gehen in die entsprechenden Hydroxo-Komplexe über. Die Stabilitätskonstanten der Hydroxo-Komplexe wurden für konstante Temperatur (27 ± 1°C) und Ionenstärke (I=0.1M KNO₃) berechnet. Die relative Reihung bezüglich der Stabilitäten ergab sich folgendermaßen: La(III)     

Elektrometrische Untersuchungen an Uranylkomplexen mit Diisopropylaminoäthanthiolhydrochlorid

The complexes of uranyl ion with diisopropylaminoethanethiol hydrochloride have been investigated by potentiometric and conductometric titration techniques in aqueous 0.1 M KNO₃. It was observed that below pH 4.5, two complexes 11 and 12 are formed with considerable overlapping and the latter complex is more stable. Their log K_stab values have been computed by alternative methods and are found to be 8.33 and 7.42 at 30°C and 8.40 and 7.72 at 40°C. The values of G, H and S for complexation at 40°C are –23.25 kcal/mole, 16.46 kcal/mole and 128.0 cal/degree/mole respectively.

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Mit 4 Abbildungen     

Syntheses and spectroscopic studies of diphenylphosphinato derivatives of boron

Summary 2-Diphenylphosphinato-1,3,2-dioxaborolanes and -borinanes of the type (whereG = -CH₂CHMe-, -CH₂CH₂CH₂-, -CH₂CH₂CHMe-,-CMe₂CMe₂-, -CMe₂CH₂CHMe-,-CH₂CMe₂CH₂-, -CH₂CEt₂CH₂-, and -C₆H₄-) are obtained by the reaction of diphenylphosphinic acid with the corresponding 2,2-oxo-bis-1,3,2-dioxaborolanes and-borinanes. The products are white crystalline solids, which have sharp melting points and are hydrolytically stable. They have been characterized by elemental analysis, IR and multinuclear NMR (¹¹B,³¹P, and¹¹⁹Sn) studies. The data suggest structures with monodentate phosphinato moieties and 3-coordinated boron atoms.

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Synthesen und spektroskopische Untersuchungen von Diphenylphosphinatoderivaten von Bor

Zusammenfassung 2-Diphenylphosphinato-1,3,2-dioxaborolane und -borinane des Typs (mitG = -CH₂CHMe-, -CH₂CH₂CH₂-,-CH₂CH₂CHMe-, -CMe₂CMe₂-,-CMe₂CH₂CHMe-, -CH₂CMe₂CH₂-, -CH₂CEt₂CH₂- und C₆H₄) erhält man durch Reaktion von Diphenylphosphinsäure mit den entsprechenden 2,2-Oxo-bis-1,3,2-dioxaborolanen und -borinanen. Die Produkte sind weiße, kristalline, hydrolyseunempfindliche Festkörper. Sie wurden mittels Elementaranalyse, IR-Spektroskopie und multinuklearer NMR-Spektroskopie (¹¹B,³¹P und¹¹⁹Sn) charakterisiert. Die Resultate legen Strukturen mit monodentaten Phosphinatoeinheiten und dreifach koordinierten Boratomen nahe.

     

A high yielding, one-pot synthesis of dialkyl carbonates from alcohols using Mitsunobu’s reagent

A Mitsunobu-based protocol has been developed for the synthesis of symmetrical and unsymmetrical dialkylcarbonates from a variety of primary, secondary and tertiary alcohols using gaseous carbon dioxide, in good to excellent yields. This protocol is mild and efficient compared to other reported methods.     

Covariant holographic entanglement negativity

We propose a covariant holographic conjecture for the entanglement negativity of bipartite mixed states in \((1+1)\)-dimensional conformal field theories dual to bulk non static \(AdS_{3}\) configurations. Application of our conjecture to \((1+1)\)-dimensional conformal field theories dual to bulk non extremal and extremal rotating BTZ black holes exactly reproduce the corresponding entanglement negativity obtained through the replica technique, in the large central charge limit. We briefly discuss the issue of the generalization of our conjecture to higher dimensions.     

Magneto-hydrodynamic stability of plane Poiseuille flow with flexible boundaries

MHD stability of plane Poiseuille flow between parallel flexible walls with coplaner magnetic field is analysed. The study is restricted to sufficiently low values of magnetic Reynolds number. The eigen-value problem so posed is then solved graphically and neutral curves are obtained for various sets of magnetic parameter and flexible wall parameters. The nature of influence on flow stability depends on the values of these parameters.     

Suitability of ion pump for evacuation of a closed He cycled Mössbauer cryostat

For Mössbauer studies at very low temperatures, the target holder kept at 11°K with the help of a closed He cycle Mössbauer shroud, has to be insulated by evacuating the outside enclosure surrounding the shroud. The target is kept in thermal contact with the cryostat cold finger through He gas at atmospheric pressure. This provides a vibrationless thermal contact between the two. The evacuation of the outside chamber has to be vibration free which can be accomplished by means of a suitable ion pump which is totally vibration free. However, use of Vac-ion pump here could not be made successful because the pump did not work at all after little pumping. To find out the cause of pump's failure, RGA was employed which showed the presence of He gas in the outside chamber at the time of purging of He gas in the internal chamber. The pump, however, worked efficiently again when the dry N₂ gas purged in place of Helium. This points out that totally vibration free Vac-ion pumps cannot be used for evacuation of such cryostats. Here, diffusion pump was used subsequantly taking extra precautions to minimise the vibrations.     

Potentiometrische Untersuchungen an Cu(II)- und Ni(II)-Komplexen mit gemischten Liganden

Potentiometric evidences have been cited for the formation of 1∶1∶1 ternary complexes in the systems: Cu(II)/Ni(II)-glycine-diamines [where diamines = ethylenediamine (en), propylenediamine (pn), o-phenylenediamine (phenen) and 1.8-naphthalenediamine (naphen)].