Lanthanides calixarene complex

FIGURE 4.8 X-ray structure of lanthanide calixarene complex ((La(N03)3)2 (CPw2). 

Photophysical studies have been conducted on a number of lanthanide complexes of calix[n]arenes, and a significant number of these are discussed in a recent review (79). The first europium and terbium calixarene complexes showed promising photophysical properties, with terbium luminescence lifetime of 1.5 ms and quantum yield of 0.20 in aqueous solution (80). 

Calixarene complexes with lanthanides have been developed to catalyze the homopolymerization of TMC and DTC. The complexes were synthesized from lanthanide isopropoxide and appropriate p-tcrt-butylcalix[n]arene (n = 4, 6, and 8). Based on the polar solvent effect, the end-group examination of the polymers, and NMR analyses of the growing chain, it could be concluded that the polymerizations of TMC and DTC initiated by p-tcrt-butylcalix[n]arene (n = 4, 6, and 8) complexes of Nd, La, and Y proceeded by a coordination-insertion mechanism. Cou et used scandium p-tcrt-... 

Harrowfield et al. [37-39] have described the structures of several dimethyl sulfoxide adducts of homo bimetallic complexes of rare earth metal cations with p-/e rt-butyl calix[8]arene and i /i-ferrocene derivatives of bridged calix[4]arenes. Ludwing et al. [40] described the solvent extraction behavior of three calixarene-type cyclophanes toward trivalent lanthanides La (Ln = La, Nd, Eu, Er, and Yb). By using p-tert-huty ca-lix[6Jarene hexacarboxylic acid, the lanthanides were extracted from the aqueous phase at pH 2-3.5. The ex-tractability is Nb, Eu > La > Er > Yb. 

Encapsulation of lanthanide ions in calixarene receptors. A strongly luminescent terbium(3+) complex, J. Chem, Soc. Chem, Commun. 878-879 (1990). 

Complexes of calixarenes with bipyridyl chromophores can be stabilized by the addition of anionic side arms, such as iminodiacetate units (85). Whilst the lanthanide complexes of ligands [L51]4- and [L52]4- are not soluble in water, their photophysical properties in... 

Sabbatini, N. Guardigli, M. Mecati, A. Balzani, V. Ungaro, R. Ghidini, E. Casnati, A. Pochini, A. Encapsulation of lanthanide ions in calixarene receptors. A strongly luminescent terbium(3 +) complex. J. Chem. Soc., Chem. Commun. 1990, (12), 878-879. 

AC and AEC complexation is also effected efficiently by other macrocyclic ligands such as the spherands 13, cryptospherands 14 [2.9, 2.10], calixarenes [2.38, A.6, A.23], torands [2.39], etc., some of them, for instance the spherands displaying particularly high stabilities. A special case is represented by the endohedral complexes of fullerenes in which the cation (Sr2, Ba2+, lanthanides) is locked inside the closed carbon framework [2.40],... 

Complexation studies were carried out by electrospray ionization mass spectrometry (ESI-MS) with three lanthanides (La, Eu, and Yr) at a concentration of 10 4 M, while the ratio of concentration of CPw2 versus calixarene (r = [calix]org/[Ln]aq) was varied between 0.1 and 10.165 The behavior of the three lanthanides is the same the 1 1 Ln calix-CMPO complex is always predominant in the range of concentration studied the 2 1 Ln calix-CMPO appears in the case of metal excess with a maximum for r = 0.5, while the percent of 1 2 Ln calix-CMPO increases as the concentration of ligand increases, but does not exceed 10% for r = 10. These studies show that two factors play a key role in the selectivity of CMPO derivatives, firstly the presence of phenyl groups on the phosphorus atom, which confers the selectivity to CMPO ligands, secondly the calixarene structure, which amplifies this selectivity due to its preorganization. Indeed the noncyclic derivative (Os2), in spite of the presence of phenyl units, does not display noticeable selectivity. 

Extraction by CMPO or Diphosphine Wide-rim Calixarenes Atamas et al. synthesized calixarenes in which the phosphorus atoms of four CMPO or diphosphine residues are linked to the wide rim of these calixarenes via a CH2 spacer.172 When compared with CPw2, the calixarenes CPw30 and CPo22 extract Yb more efficiently, in contrast with La and Eu, which are less effectively extracted the selectivity along the lanthanide series is less marked. Complexation measurements were carried out in methanol in the presence of NaN03 (5 10 2 M) the La and... 

It was shown that narrow-rim CMPO derivatives form stronger 1 1 lanthanide complexes than their wide-rim counterparts. However, lanthanide extraction results display a stronger extracting ability. This discrepancy can be explained by the fact that, contrary to the wide-rim CMPO calixarenes that form polymeric species, a part of less lipophilic monomeric narrow-rim CMPO calixarene piles up at the interface instead of being extracted, as predicted by Wipff for the extraction of strontium by mixed amide calixarenes (see Section 4.4.1.1). This assumption is all the more... 

L. H. Delmau, Ph.D. Thesis, Strasbourg University, 1997. Extraction of Trivalent Lanthanides and Actinides by Functionalized Calixarenes. Study of the Structure of the Complexes in Solution by Nuclear Magnetic Resonance. 

Calix[ ]arenes are a family of macrocycles prepared by condensation reactions between n /v/ra-substituted phenols and n formaldehyde molecules under either base or acid catalysis. Different sizes of the macrocycles can be obtained (n = 4-20) (Stewart and Gutsche, 1999) depending on the exact experimental conditions, which were mastered in the 1960 s (Gutsche, 1998), but the most common receptors are those with n =4,6,8 (macrocycles with an odd number of phenol units are more difficult to synthesize). We use here the simplified nomenclature in which the number of phenolic units is indicated between square brackets and para substituents are listed first.4 Calixarenes, which can be easily derivatized both on the para positions of the phenolic units and on the hydroxyl groups, have been primarily developed for catalytic processes and as biomimics, but it was soon realized that they can also easily encapsulate metal ions and the first complexes with d-transition metal ions were isolated in the mid-1980 s (Olmstead et al., 1985). Jack Harrowfield characterized the first lanthanide complex with a calixarene in 1987, a bimetallic europium complex with p-terf-butylcalix[8]arene (Furphy etal., 1987). 

Well-examined complexes include derivatives of macrocyclic polyphenols known as calixarenes [147] (Fig. 29, Table 13). Lanthanide complexes containing up to eight phenolic units (calix[8]arene) were reported. 

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