Wide rim

Schmidt, C., Saadioui, M., Bohmer, V. et al. 2003. Modification of calix[4]arenes with CMPO-functions at the wide rim. Synthesis, solution behavior, and separation of actinides from lanthanides. Org. Biomol. Chem. 1 4089 4096. 

Wide-rim tetra(CMPO) calix[4]arenes present good extraction abilities and also rather good selectivities at high acidity. But, the stability toward hydrolysis is not very good. N-methylated compounds exhibit low extraction efficiency, but higher stability toward hydrolysis when they are in contact with strong nitric acid (3 M). 

Tetra(CMPO) cavitands present nearly the same extraction properties as wide-rim tetra CMPO calix[4]arenes, but a slightly lower selectivity. 

The ligands initially considered are the conformationally mobile dimethoxy-calix[4] arene-crown-6 and its counterpart bearing a tert-butyl moiety wide-rim. Each has be considered in three conformations cone, partial cone, and 1,3 alternate in the free state and then complexed by Na, K, Rb, and Cs. The conclusions are summarized below. 

Extraction by Wide-Rim CMPO Calix[4]arenes and Oligomers... 

Stability Constants (log Pv) of Europium Complexes with Wide-Rim CMPO Calix[4]arenes and Linear Counterparts in Methanol (/= 0.05 M NaN03)... 

Distribution Ratios for Eu, Np, Pu, and Am from Aqueous Solutions 4 M NaN03,1 M HN03 into a NPHE Solution of Linear Oligomers or Calixarenes Bearing the CMPO Moieties on the Wide Rim (10-3 M)... 

All the complexes metal wide-rim CMPO calix[4]arene studied by crystallographic analysis have the 2 1 Micalix stoichiometry. Cations are complexed by two bidentate CMPO, which keep them apart from the cavity of the calix[4]arene. Thus, these complexes are not real inclusion complexes (Figure 4.8). 

Cavitands, prepared by the Twente group, differ from the wide-rim CMPO calixarene not only by the basic scaffold, but also by the distance to the rim and in the amido function (tertiary amide versus secondary amide). In comparison to CMPO calixarenes, compounds Cvl and Cv2 did not lead to improvements in terms of extracting ability or selectivity.17169... 

Extraction by Wide-rim N-methylated CMPO Calixarenes Two calix[4]arene tetraethers (pentoxy CPwl7 and tetradecyloxy CPwl8) bearing four -N(Me)-C0-CH2-P(0)Ph2 residues on their wide-rim were synthesized for the first time.170 Their ability to extract lanthanides and actinides from an acidic aqueous... 

Extraction by Sulfur Derivatives of Wide-rim CMPO Calixarenes... 

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... 

The grafting of CMPO moieties on the narrow rim affords a strong decrease of extracting ability toward lanthanides, trivalent actinides, and tetravalent plutonium from acidic solutions. The distribution ratios for the different calixarenes in NPHE are low, except for CPn3 for which the number of carbon atoms in the spacer is four, but even for this compound, the distribution ratios are lower than those obtained with their wide-rim counterparts (Figure 4.11). 

This difference of behavior of calixarenes bearing CMPO residues either on the wide rim or on the narrow rim was confirmed by extraction of europium (from nitric acid solutions by CPw2 and CPn2 diluted in chloroform) by implementing ESI-MS for the two calixarenes. Complexes with 1 1 and 1 2 Eu calix-CMPO stoichiometry were evidenced. The major species for CPw2 is the 1 2 complex, while for CPn2 the predominant complex is the 1 1 complex.165... 

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... 

The adamantyl unit provides several positions for the introduction of additional substituents, which opens the road for the further development of this type of ligand (possible fine-tuning of selectivity, creation of new binding sites at the wide rim, etc.). 

As for wide-rim CMPO calixarenes, the extraction ability for all the ada-mantyl-calixarene ligands is much better than for their monomeric analogues (CAdll, CAdl2) and DiOCMPO. 

All calixarenes bearing CMPO residues on the wide rim display a higher affinity for thorium. The hexamer CAd4 is the most effective for thorium, while lanthanides are better extracted by CAd2. Without spacers (CAdl), the ligating CMPO functions... 

The wide-rim CMPO calix[4]arenes are the most efficient compounds for the extraction of trivalent actinides and lanthanides. They are also the compounds that display the highest selectivity along the lanthanide series, provided that phosphorus atoms are linked to phenyl groups. They also display a higher selectivity than the calixarene-bearing diphosphine oxide, where the phosphorus atom is linked to phenyl units CPo21.176- ... 

Since in the case of p-H calixarenes, a precipitate occurred at the water/organic interphase, extraction tests were carried at a concentration of 10" M for these compounds. The presence of tert-butyl or benzyloxy at the wide rim helps to solubilize the complexes. The distribution ratios are compared to wide-rim CPw3 and narrow-rim CPn3 (Table 4.34).179 For all CMPO-calix[6,8]arenes, distribution ratios of the two cations studied (Eu and Am) increase with increasing HN03 concentration, in agreement with what is observed with tetramers bearing CMPO residues... 

In collaboration with the Mainz group, Parma University workers synthesized CMPO-calix[6]arenes CP64 and CP65, bearing three CMPO binding sites onto the narrow and wide rim, respectively. CP65 and to a lesser extent CP64 display relatively low distribution ratios and a selectivity SAm/Eu lesser than 2.5.18... 

Extraction by Wide-Rim Calixarenes Bearing One to Three CMPO Residues... 

Bohmer et al. also synthesized calixarenes bearing one or more CMPO moieties and another functionality (malonamide or carboxylate). These calixarenes display lower extracting ability than CPw3, and contrary to expectations, these functions do not lead to a new order of selectivity. Calix[4]arenes bearing one or two adjacent malonic acid groups (NH-C(0)-CH2-C00H) adjacent to CMPO functions at the wide rim were unstable and decomposed during the complex-ation studies. 

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