Extraction of americium and europium by CMPO-substituted adamantylcalixarenes

Summary Eight p-adamantylcalix[4]arene derivatives, bearing four CMPO-like functions [(CH2)nNHC(O)CH2- P(O)Ph2] at the wide (4a,b, n = 0, 1) or narrow (5a–c and 6a–c, n = 2–4) rims were synthesized for the first time. Studies of the extraction of americium(III) and europium(III) from 3 M HNO3 solutions to organic phases (dichloromethane, m-nitro-trifluoromethylbenzene) showed: (i) The extraction ability for all the adamantylcalixarene ligands is much better than for their monomeric analogues –N-(1-adamantyl)-, N-(1-adamantylmethyl)- and N,N-(dibutyl)carbamoylmethyldiphenylphosphine oxides 7a, 7b, 8; (ii) The extraction percentage increases strongly with increasing length of the spacer for all types of ligands 4–6, and best extraction results were found for 4b (n = 1) and 5c (n = 4); (iii) The separation coefficient D Am/D Eu for the investigated compounds did not exceed 2, which is close to the narrow rim CMPO calixarenes, studied earlier; (iv) Variation of the spacer length between CMPO groups attached to the 1,3- and 2,4-positions of the calixarene platform in 6 did not lead to appreciably improved extractants, neither with respect to the extraction abilities (D) nor to the selectivities (D Am/D Eu).