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Trivalent Lanthanides (trivalent + lanthanide)

Distribution by Scientific Domains

Chemistry	60%

Selected Abstracts

Ln3NS3 (Ln: La,Nd, Sm, Gd,Dy): Structure and Magnetism of 3:1:3-Type Nitride Sulfides of Trivalent Lanthanides.

CHEMINFORM, Issue 49 2006
Falk Lissner
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Kinetics of Bis(p -nitrophenyl)phosphate (BNPP) Hydrolysis Reactions with Trivalent Lanthanide Complexes of N -Hydroxyethyl(ethylenediamine)- N,N,,N, -triacetate (HEDTA),

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2009
C. Allen Chang
Abstract Kinetic studies of hydrolysis reactions of BNPP [sodium bis(p -nitrophenyl)phosphate] with trivalent lanthanide (Ln3+) complexes of HEDTA [HEDTA = N -hydroxyethyl(ethylenediamine)- N,N,,N, -triacetate] were performed at pH 6.96,11.34 and 25 °C by a spectrophotometric method and by HPLC analysis. The reaction rates increase with increasing atomic number of lanthanide and solution pH from PrHEDTA to EuHEDTA and then decrease for heavier LnHEDTA complexes. Plots of pseudo-first-order rate constants (kobs) vs. pH could be fitted to the equation kobs = kLnL(OH)[LnL]T/{1,+,exp[,2.303(pH,,,pKh)]}, where kLnL(OH) is the rate constant for the reaction of LnHEDTA(OH), with BNPP, Kh is the hydrolysis constant of LnHEDTA, and [LnL]T is the total concentration of LnHEDTA. The pKh values obtained by the kinetic method are in the range 8.2,10.3 and are similar to those measured by potentiometric methods. At [LnL]T = 10,70 mM and pH 10.5, most of the observed pseudo-first-order rate constants could be fitted to a simple saturation kinetic model, kobs = k1K[LnHEDTA(OH),]/{1 + K[LnHEDTA(OH),]}, where K is the equilibrium constant for the formation for LnHEDTA(OH),BNPP and is in the range 2,147 M,1. The k1 values are in the range 1.12,×,10,5,2.71,×,10,3 s,1. The kobs data for TbHEDTA and HoHEDTA were fitted to a quadratic equation. It was observed that the dinuclear species are more reactive. ESI mass spectrometry confirmed that the reaction between BNPP and EuHEDTA is a simple hydrolysis but not a transesterification, presumably because the three inner-sphere coordinated water molecules are far away from the coordinated hydroxyethyl group. Hydrolysis is likely to occur by proton transfer from one inner-sphere coordinated water molecule to the deprotonated ethyl oxide group followed by nucleophilic attack of the resulting hydroxide ion on the bonded BNPP anion.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

A new set of electronegativity scale for trivalent lanthanides

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007
Keyan Li
Abstract A new set of electronegativity (EN) scale for all trivalent lanthanides (Ln) is proposed on the basis of effective ionic potential, from which the electron-attracting power of trivalent Ln can be well differentiated. This new scale can be used to qualitatively explain the valence stability and valence change of some typical trivalent Ln. Furthermore, the good linear relationships of the charge-transfer energy of Ln3+ and the first dehydroxylation temperature in the agardite to the current EN scale of Ln3+ show us the further reasonableness of our new EN scale. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Tuning the Polarization Along Linear Polyaromatic Strands for Rationally Inducing Mesomorphism in Lanthanide Nitrate Complexes

CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2007
Emmanuel Terazzi Dr.
Abstract The opposite orientation of the ester spacers in the rodlike ligands L,4C12 (benzimidazole-OOC-phenyl) and L,5C12 (benzimidazole-COO-phenyl) drastically changes the electronic structure of the aromatic systems, without affecting their meridional tricoordination to trivalent lanthanides, LnIII, and their thermotropic liquid crystalline (i.e., mesomorphic) behaviors. However, the rich mesomorphism exhibited by the complexes [Ln(L,4C12)(NO3)3] (Ln=La,Lu) vanishes in [Ln(L,5C12)(NO3)3], despite superimposable molecular structures and comparable photophysical properties. Density functional theory (DFT) and time-dependant DFT calculations performed in the gas phase show that the inversion of the ester spacers has considerable effects on the electronic structure and polarization of the aromatic groups along the strands, which control residual intermolecular interactions responsible for the formation of thermotropic liquid-crystalline phases. As a rule of thumb, an alternation of electron-poor and electron-rich aromatic rings favors intermolecular interactions between the rigid cores and consequently mesomorphism, a situation encountered for L,4C12, L,5C12, [Ln(L,4C12)(NO3)3], but not for [Ln(L,5C12)(NO3)3]. The intercalation of an additional electron-rich diphenol ring on going from [Ln(L,5C12)(NO3)3] to [Ln(L,6C12)(NO3)3] restores mesomorphism despite an unfavorable orientation of the ester spacers, in agreement with our simple predictive model. [source]