Lanthanide complexes glycolates

It is appropriate to consider the relative stability of lanthanide conq)lexes as a first indicator of a ligand s potential applicability for lanthanide separations. In fig. 9 is shown a plot of the relative stability of a variety of lanthanide carboxylate complexes (normalized to log/ (Gd )=0) of importance in ana ical separations. The 1 2 complexes of the lanthanides with glycolate and digjtycolate exhibit similarly poor discrimination of lanthanide ions between Gd and Ho, though the overall slope is greater for diglycolate. The 1 2 lactate complexes vary more regularly than these species, but... 

A practical application of the spectral intensity of hypersensitive transitions in lanthanide ions is the determination of stability constants. Bukietynska et al. (1977, 1981a,b) have evaluated the stability constants of lanthanide complexes from the changes of the oscillator strength of hypersensitive transitions as a function of the ligand concentration. The method was applied to acetate, propionate, glycolate, lactate and a-hydroxyisobutyrate complexes of Nd ", Ho and Er +. Bukiet5mska et al. claim that this spectrophotometric method is superior to the potentiometric method, since the best results for the latter method can be obtained only for the first complexation steps. The stability constants evaluated at several temperatures have been used also to calculate the thermodynamic quantities AG, AH and AS. 

A transition from tris-glycolates->tris-glycolate dihydrate or hydroxyacetate-oxyacetate may be followed by a decrease in van der Waals repulsion, and the decrease is large for elements with small ionic radius. Thus the observations that the lanthanides with smaller ionic radius form the tris-glycolate dihydrates or hydroxyacetate-oxyacetate complexes 150,151) and have lower CN can be rationalized. A decrease in stability due to short oxygen-oxygen contacts is not an unique feature for the anhydrous tris-glycolates, but may be. an important property. 

Figure 1. Entropy of formation of the monoligand complex as a function of the atomic number of the lanthanides for EDTA, fluoride, acetate, and glycolate ligands...

Macrocycle complexation chemistry 35. Survey of the complexation of the open chain 15-crown-5 analogue tetraethylene glycol with the lanthanide chlorides, R. D. Rogers, R. D. Etzenhouser, J. S. Murdoch and E. Reyes, Inorg. Chem., 1991, 30, 1445. 

Structural investigation into the steric control of polyether complexation in the lanthanide series - macrocyclic 18-crown-6 versus acyclic pentaethylene glycol, R. D. Rogers, A. N. Rollins, R. D. Etzenhouser, E. J. Voss and C. B. Bauer, Inorg. Chem., 1993, 32, 3451. 

Remarkable linear correlation, often preserving the generic form of the inclined W for various properties like M—N stretching frequencies of the 2,2 -dipyridyl complexes, lattice parameters of M203, MOBr, molecular volume(V/Z) for the trigonal glycolate complexes of the lanthanides with their L-values has already been observed (55). We would like to show here a few more correlation of the miscellaneous properties of the lanthanides with their L-values. 

Toraishi, T., Farkas, L, Szabo, Z., Grenthe, I., Complexation of Th(IV) and various lanthanide(III) ions by glycolic acid potenti-... 

Fig. 7 Metallo-supramolecular polymer gels as introduced by Rowan and coworkers, (a) Organogels formed by complexation of lanthanide and transition metal ions to 2,6-bis (l-methylbenzimidazolyl)pyridine (BIP)-functionalized poly (ethylene glycol), (b) Thermo- and mechanoresponsiveness of these gels. Reprinted with permission from [134]. Copyright 2003 American Chemical Society...

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