Home About us Contact
|
Home About us Contact | ||
|
|
||
Lanthanide Metal Ions (lanthanide + metal_ion)
Selected AbstractsModulation of the Lifetime of Water Bound to Lanthanide Metal Ions in Complexes with Ligands Derived from 1,4,7,10-Tetraazacyclododecane Tetraacetate (DOTA)HELVETICA CHIMICA ACTA, Issue 5 2005Shanrong Zhang A series of di- and tetraamide derivatives of DOTA were synthesized, and their lanthanide(III) complexes were examined by multinuclear 1H-, 13C-, and 17O-NMR spectroscopy, and compared with literature data of similar, known complexes (Table). All ligands formed structures similar to the parent [LnIII(DOTA)], complexes, with four N-atoms and four O-atoms from DOTA and one O-atom from the inner-sphere water molecules. Interestingly, the lifetimes ,M of the inner-sphere, metal-bound water molecules vary widely, ranging from nano- to milliseconds, depending on the identity of the pendent amide side chains. In general, positively charged [LnIII(DOTA-tetraamide)]3+ complexes display the longest residence times (high ,M values), while complexes with additional charged functional groups on the extended amides display much smaller ,M values, even when the side groups are not directly coordinated to the central Ln3+ ions. The design of novel [LnIII(DOTA-tetraamide)]3+ complexes with a wide, tunable range of ,M values is of prime importance for the application of fast-responding, paramagnetic chemical-exchange-saturation-transfer (PARACEST) imaging agents used for the study of physiological and metabolic processes. [source] Template Synthesis, Crystal Structure and Luminescent Properties of Neutral N4O3 Tripodal LnIIIL Complexes (LnIII = La3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+ or Lu3+; H3L = Tris{[3,-(2,,-pyridyl)-5,- tert -butyl-2,-hydroxybenzylidene-2-imino]ethyl}amine)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2004Wai-Kwok Wong Abstract In the presence of Ln3+ (Ln = La, Eu, Gd, Tb, Dy, Ho, Er, Tm or Lu), tris(2-aminoethyl)amine condensed with three equivalents of 3-(2,-pyridyl)-5- tert -butyl-2-hydroxybenzaldehyde in methanol to give the neutral Schiff-base complex LnIIIL (Ln = La 1, Eu 2, Gd 3, Tb 4, Dy 5, Ho 6, Er 7, Tm 8 and Lu 9; H3L = tris{[3,-(2,,-pyridyl)-5,- tert -butyl-2,-hydroxybenzylidene-2-imino]ethyl}amine). The structures of compounds 4,7 were determined by X-ray crystallography. The crystal structure analyses revealed that the Schiff base behaves as a tri-deprotonated heptadentate ligand encapsulating the lanthanide metal ion within the N4O3 cavity, with all the pyridyl groups being pendant. Solution spectroscopic data suggest that the LnIIIL complexes remain intact in methanol and exist as nine-coordinate non-electrolytes with the lanthanide metal ions coordinated to the N4O3 cavity of the tripodal Schiff base and two solvent molecules. The solution photoluminescent properties of these lanthanide Schiff-base complexes were also examined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Dinuclear Zn(II) catalysts as biomimics of RNA and DNA phosphoryl transfer enzymes: changing the medium from water to alcohol provides enzyme-like rate enhancementsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2010R. Stan Brown Abstract Phosphodiesters are notoriously hydrolytically inert compounds that are demonstrated to have large accelerations of P-OR cleavage promoted by transition and lanthanide metal ions in methanol and ethanol media. This review commentary describes recent findings of how a simple mononuclear and a dinuclear Zn(II) complex promote the cleavage of a series of RNA models and DNA models in alcohol media. The discussion centers on the analysis of the mechanisms of cleavage, energetics of the catalytic process, on recent findings of electrophilic assistance of leaving group departure, and the observation of a rapid hydrolytic reaction of a DNA model promoted by the dinuclear Zn(II) complex in ethanol containing less than 2% water. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||