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RESEARCH PRODUCT

Aminoalkylbis(phenolate) [O,N,O] donor ligands for uranyl(VI) ion coordination: Syntheses, structures, and extraction studies

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Abstract The syntheses of five new aminoalkylbis(phenolate) ligands (as hydrochlorides) and their uranyl complexes are described. The reaction between uranyl nitrate hexahydrate and phenolic ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminopropane) · HCl], H2L1 · HCl, forms a uranyl complex [UO2(HL1)2] · 2CH3CN (1). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminobutane) · HCl], H2L2 · HCl, forms a uranyl complex with a formula [UO2(HL2)2] · 2CH3CN (2). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methyl benzyl)-1-aminohexane) · HCl], H2L3 · HCl, yields a uranyl complex with a formula [UO2(HL3)2] · 2CH3CN (3) and the ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-cyclohexylamine) · HCl], H2L4 · HCl, yields a uranyl complex with a formula [UO2(HL4)2] (4). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-benzylamine) · HCl], H2L5 · HCl, forms a uranyl complex with a formula [UO2(HL5)2] · 2MeOH (5). The molecular structures of 1, 2′ (2 without methanol), 3, 4 and 5 were verified by X-ray crystallography. The complexes 1–5 are neutral zwitterions which form in a molar ratio of 1:2 (U to L) in the presence of a base (triethylamine) and bear similar mononuclear, distorted octahedral uranyl structures with the four coordinating phenoxo ligands forming an equatorial plane and resulting in a centrosymmetric structure for the uranyl ion. In uranyl ion extraction studies from water to dichloromethane with ligands H2L1 · HCl–H2L5 · HCl, the ligands H2L2 · HCl and H2L4 · HCl are the most effective ones.