- Formation and uses of europium complexes
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The present invention provides a method of forming an oxidatively-stable aqueous Eu(II) complex by synthesizing ligands that coordinate to large, soft, electron rich metals like Eu(II). The invention also provides an oxidatively stable aqueous Eu(II) complex. The complex can be used for a variety of purposes some of which include, but are not limited to, in paramagnetic chemical exchange saturation transfer, as a medical diagnostic, as a semiconductor, and for use in forming materials.
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- Oxidatively stable, aqueous europium(II) complexes through steric and electronic manipulation of cryptand coordination chemistry
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A series of cryptands has been prepared and they demonstrate the relationship between oxidative stability of aqueous EuII and ligand properties (see figure). One of these EuII complexes is more stable than FeII in hemoglobin and appears to be the most oxidatively-stable aqueous EuII species known. The high stability of EuII is expected to enable the use of the unique magnetic and optical properties of this ion in vivo.
- Gamage, Nipuni-Dhanesha H.,Mei, Yujiang,Garcia, Joel,Allen, Matthew J.
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supporting information; experimental part
p. 8923 - 8925
(2011/02/23)
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- Solvent Dependence of Kinetics and Equilibria of Thallium(I) Cryptates in relation to the Free Energies of Solvation of Thallium(I)
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Stability constant and dissociation rate constants of thallium(I) cryptates have been measured in several solvents at 25 deg C.The Tl+ cryptates are more stable and less sensitive to ligand cavity size than the corresponding complexes of the al
- Cox, Brian G.,Stroka, Jadwiga,Schneider, Irmgard,Schneider, Hermann
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p. 187 - 198
(2007/10/02)
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- Kinetics of Ligand-exchange Reactions of Macrobicyclic Cryptands
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The rate constants for exchange reactions between metal cryptate complexes, MCry1(n+), and a free cryptand, Cry2, have been determined in several solvents.Two mechanisms could be distinguished: a reaction proceeding via the free metal cation following dissociation of MCry1(n+), and a direct, bimolecular cation exchange between the two ligands.In solvents such as water, dimethylsulphoxide and dimethylformamide, which interact strongly with cations, the former pathway predominates for alkali-metal and alkaline-earth-metal cryptates.In poorly solvating media such as methanol and propylene carbonate, where dissociation rate constants are very low, bimolecular pathways make an important contribution to the overall exchange pathway.Exchange reactions of Ag(1+) cryptates show ligand-dependent rates and strong saturation effects in both methanol and dimethylsulphoxide.
- Cox, Brian G.,Troung, Nguyen van,Schneider, Hermann
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p. 3285 - 3294
(2007/10/02)
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- Alkaline Earth Cryptates: Dynamics and Stabilities in Different Solvents
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The stability constants and rates of formation and dissociation of alkaline earth cryptates with (2,1,1), (2,2,1), (2,2,2), (2B,2,2), and (2B,2B,2) have been measured in several solvents.The stability constants, Ks, are considerably larger and display higher selectivity than those of the monocyclic crown and diaza crown ethers and anionic ionophores.Values of Ks vary by over 10 orders of magnitude in the different solvents, increasing in the order Me2SO d).The rates show no correlation with solvent exchange rates, and are sensitive to cation size, cation-solvent interactions, and ligand flexibility.In strongly solvating media such as Me2SO, rates are up to 106 lower than predicted by a simple Id mechanism.The results suggest that the complexation reaction involves essentially stepwise replacement of solvent by ligand donor atoms, but that even for relatively flexible macrocyclic ligands compensation for loss in solvation by ligand binding energy in the transition state is not complete.
- Cox, B. G.,Truong, Ng van,Schneider, H.
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p. 1273 - 1280
(2007/10/02)
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