Extraction and Complexation of Alkali, Alkaline Earth, and F-Element Cations by Calixaryl Phosphine Oxides

Abstract

A series of new calixarene derivatives with phosphine oxide groups on the lower rim and, for comparison, a series of noncalixarene phosphine oxides have been synthesised. Their extraction power for alkali and alkaline earth cations from aqueous metal picrate solution into dichloromethane have been determined as well as the stability constants in methanol of the 1:1 complexes of several members of the calixarene series. Important selectivity trends are revealed by both methods. The extraction power from aqueous nitrate solutions (1m in HNO 3 ) towards europium(iii), as a model for trivalent actinides, and thorium(iv), as a model for tetravalent actinides, has been studied in detail for eight symmetrical calixarene derivatives, which differ in either calixarene size (4, 5, 6 or 8), the substituent at the upper rim (tert-butyl or hydrogen) or the number of methylene groups separating the phenolic oxygen atoms from the phosphorus atoms (1 or 2). The stoichiometry of the extracted species was characterised by a classical log ± log plot analysis. All the calixarenes tested are far better extractants than typical noncalixarene extractants, for example, TOPO and CMPO, currently in use in the treatment of radioactive waste; they extract thorium better than europium. The influence of the nitric acid concentration and of the sodium nitrate concentration in the aqueous phase on the extraction efficiency was also examined in order to assess the possible application of these compounds for the decategorisation of liquid nuclear waste. Several thorium complexes have been characterised by their stability constants in methanol.

Extractants for rare earth metals

“…Therefore, the idea of joining of phosphoryl group on the hard platform of calixarene arose to take advantage of synergistically effect for increasing the efficiency and selectivity of extraction [18]. Previously it has already been well studied and calixarene derivatives containing carbamoylmetylphosphin oxides in different positions of the calixarene fragments were described [19,20], as well as some calixarenes with their phosphine oxides at the lower rim [21,22].…”

“…Из ряда каликсаренов с фосфи-новыми заместителями по нижнему ободу 32а, 32б, 33а и 34а наибольшей экстракционной эффективностью для ски используя γ-излучение соответст-вующих изотопов [22]. Еще один пример синтеза селек-тивных экстрагентов на основе ка-ликс [4]арена для разделения актинои-дов от лантаноидов был описан Ansari и сотрудниками [24,25].…”

From Simple Rings to One‐Dimensional Channels with Calix[8]arenes, Water Clusters, and Alkali Metal Ions.

“…Calix [n]arenes are known for their excellent coordination 1 and extraction [2][3][4] capacities, [1][2][3][4] and have been studied as model systems for the design of catalysts 5 and sensing receptors. 6 Weak interactions involving both their OH groups and aromatic rings can give rise to complicated supramolecular arrangements.…”

“…[7][8][9] In addition to the large choice of ring sizes, calixarenes can adopt different conformations, which can be tuned by substituents at the upper and/or lower rims. In the calixarene family, calix [4]arenes have been the most intensively studied, 10 while calix [8]arenes remain comparatively little investigated in the solid state. 11 This is certainly due to different reasons such as limited solubility, poor control over stereoselective substitution reactions at the two rims, and finally the high flexibility of the molecules itself, which allow a large variety of structural conformations and hence hinder long-range order in the solid state.…”

“…11 This is certainly due to different reasons such as limited solubility, poor control over stereoselective substitution reactions at the two rims, and finally the high flexibility of the molecules itself, which allow a large variety of structural conformations and hence hinder long-range order in the solid state. While calix [4]arenes can be observed in four conformations (cone, partial cone, 1,2-alternate or 1,3-alternate) in solution, calix [8]arenes can adopt in principle more conformations, although the 'pleated loop' conformation is favored even in solution because of intramolecular hydrogen bonding by the OH groups. 12 This hydrogen bond stabilization may be weakened upon metallation of the hydroxide groups, leading to more flexible conformations.…”