Calixarene‐Based Picolinamide Extractants for Selective An/Ln Separation from Radioactive Waste

Calix[6]arene‐Picolinamide Extractants for Radioactive Waste Treatment: Effect of Additional Carboxy Binding Sites in the Pyridine 6‐Positions on Complexation, Extraction Efficiency and An/Ln Separation

“…We previously demonstrated [9] that lower-rim picolinamide calix [n]arenes (e.g., L1-L3) can be efficiently synthesised through reaction with the pentafluorophenyl esters of picolinic acids. Following a similar strategy, we prepared pentafluorophenyl esters 11-14 (Scheme 1) by treating picolinic acids (7)(8)(9)(10) modified in the 6-position with methyl ester, benzyl ester, diethylacetamido or acetylamino groups, respectively, with dicyclohexylcarbodiimide (DCC) and pentafluorophenol (68-99 % yield).…”

“…We previously found that calixarenebased picolinamide ligands (e.g., L1-L3) are rather efficient and selective (separation factors SF Am/Eu = D Am / D Eu Յ 11.4), at least up to [HNO 3 ] = 10 -2 /10 -3 . [9] More recently, we also showed that calixarene-based picolinamide ligands having electron-withdrawing groups in the para position of the pyridine nuclei are able to extract trivalent metal ions into the organic phase even at higher nitric acid concentrations. [19] Although it is well known that the introduction of additional binding sites such as carboxylic acid, ester or amide groups in the ortho position to the heterocy-clic N atom of pyridine, [20,21] bipyridine [22] and phenanthroline [23] strongly increases their coordination ability toward highly charged lanthanide and actinide metal ions, nothing is known, to the best of our knowledge, on their effect on An/Ln selectivity.…”

“…It was demonstrated that the preorganisation of binding groups on macrocycles [8] such as calixarenes, [9][10][11][12][13][14][15] resorcarenes [16] or tripodal scaffolds [17,18] strongly enhances the efficiency in extraction. We previously found that calixarenebased picolinamide ligands (e.g., L1-L3) are rather efficient and selective (separation factors SF Am/Eu = D Am / D Eu Յ 11.4), at least up to [HNO 3 ] = 10 -2 /10 -3 .…”

Extractants for rare earth metals

“…The synthesis of calix [4]arene-BDGA 43 was carried out in accordance with a scheme where the compounds 40 and 42 were obtained by previously described methods [28,29]. The study of the extraction of Am(III) and Eu(III) from the solution of nitric acid by the compound 43 was conducted using 95% kerosene/5% n-octanol as diluent.…”

“…Синтез каликс [4]арен-BDGA 43 осуществлен в соответствии со схе-мой, где соединения 40 и 42 были по-лучены по ранее описанным методи-кам [28,29].…”