Uranyl ion complexes with long chain aminoalcoholbis(phenolate) [O,N,O,O′] donor ligands

The reaction between uranyl nitrate hexahydrate and phenolic ligand precursor [(N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-4-amino-1-butanol) · HCl], H3L1 · HCl, leads to a uranyl complex [UO2(H2L1)2] (1a) and [UO2(H2L1)2] · 2CH3CN (1b). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-4-amino-1-butanol)H3L2 · HCl], H3L2 · HCl, yields a uranyl complex with a formula [UO2(H2L2)2] · CH3CN (2). The ligand [(N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-5-amino-1-pentanol) · HCl], H3L3 · HCl, produces a uranyl complex with a formula [UO2(H2L3)2] · 2CH3CN (3) and the ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-5-amino-1-pentanol) · HCl], H3L4 · HCl, leads to a uranyl complex with a formula [UO2(H2L4)2] · 2CH3CN (4). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-6-amino-1-hexanol) · HCl], H3L5 · HCl, leads to a uranyl complex with a formula [UO2(H2L5)2] · 4toluene (5). The complexes 1–5 are obtained using a molar ratio of 1:2 (U to L) in the presence of a base (triethylamine). The molecular structures of 1a, 1b, 3, 4 and 5 were verified by X-ray crystallography. All complexes are neutral zwitterions and have similar centrosymmetric, mononuclear, distorted octahedral uranyl structures with the four coordinating phenoxo ligands in an equatorial plane. In uranyl ion extraction studies from water to dichloromethane with ligands H3L1 · HCl–H3L5 · HCl, ligands H3L1 · HCl, H3L4 · HCl and H3L5 · HCl are the most effective ones.

Graphical abstractThe reaction between uranyl nitrate hexahydrate and phenolic ligand precursors N,N-bis(2-hydroxy-3-methyl-5-alkylbenzyl)-4-aminobutanol (alkyl = methyl or t-butyl), N,N-bis(2-hydroxy-3-methyl-5-alkylbenzyl)-5-aminopentanol (alkyl = methyl or t-butyl) and N,N-bis(2-hydroxy-3-methyl-5-alkylbenzyl)-6-aminohexanol (alkyl = t-butyl) (H3L1–H3L5) or their hydrochlorides in acetonitrile in presence of the base affords the mononuclear, neutral complexes [UO2(H2L)2] · xCH3CN (x = 0, 1 or 2). Extraction studies of the uranyl ion from water to dichloromethane with these new ligands (H3L1–H3L5) are also presented.Figure optionsDownload full-size imageDownload as PowerPoint slide