Uranyl Complexes of Alkyl-Bridged Ditopic Diaminotetraphenol Ligands and Their Use as Uranyl Ion Extractors

The coordination chemistry of uranyl ions was studied using long n-alkyl chain (n = 5-8) bridged by N,N,N',N'-tetrakis(2-hydroxy-3-methyl-5-tert-butylbenzyl)diaminoalkanes (H(4)L1 H(4)L4) as ligands. All ligands formed 2:1 (U-to-L ratio) complexes with uranyl ions, but in addition 1:1 complexes could be characterized using ligands H(4)L2 and H(4)L3. The complexes were characterized by elemental analysis, spectroscopy (IR and NMR), and Xray diffraction. The 2:1 complexes are of two types: [(UO2)2(H(2)Lm)(NO3)(2)(solvent)(2)] (m = 1 and 2; solvent = ethanol or propanol) or (cation)(2)[(UO2)(2)(H(2)Lm)(NO3)(2)(anion)(2)].xsolvent (m = 2 and 4; cation = triethylammonium, anion = nitrate or thiocyanate, and solvent = dichloromethane and acetonitrile; x = 1 or 2). The 1:1 complexes have the formula (UO2)(2)(H(2)Lm)(2)] (m = 2 and 3). In the solid state, 2:1 complexes are almost in a linear conformation with the uranyl ion at both ends of the ligand. The 1:1 complexes are cyclic dinuclear molecules. Preliminary studies of the ligands as uranyl ion extractors from water to dichloromethane were also performed. A high extraction efficiency was observed with H(4)L3 for uranyl ions, and in the presence of Cu-II, Co-II, and Zn-II ions, a good extraction selectivity for uranyl ions was found with H(4)L1.