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

Abstract

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 (H4L1-H4L4) 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 H4L2 and H4L3. The complexes were characterized by elemental analysis, spectroscopy (IR and NMR), and X-ray diffraction. The 2:1 complexes are of two types: [(UO2)2(H2Lm)(NO3)2(solvent)2] (m = 1 and 2; solvent = ethanol or propanol) or (cation)2[(UO2)2(H2Lm)(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(H2Lm)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 H4L3 for uranyl ions, and in the presence of Cu(II), Ni(II), Co(II), and Zn(II) ions, a good extraction selectivity for uranyl ions was found with H4L1.

Synthesis, structural investigation and kinetic studies of uranyl(VI) unsymmetrical Schiff base complexes

“…It seems that the charge transfer band (LMCT) from oxide (=O) to uranyl occurred at lower frequencies (higher wavelengths) than the Schiff base 2− →U(VI). 3 …”

The crystal structure of the zwitterionic co-crystal of 2,4-dichloro-6-{[(3-hydroxypropyl)azaniumyl]methyl}phenolate and 2,4-dichlorophenol

“…The flexible C-N bond in these ligands offers a tractable three-dimensional structure when coordinated to different metal centres (Riisiö et al, 2012). This provides numerous applications, particularly in enzyme mimicking and catalysis, as well as extraction of trace metals (Maurya et al, 2015;Riisiö et al, 2013;Lee et al, 2010). In the present study, we wanted to prepare a tripodal amino (bis) phenolate Mannich base derived from 3-propanol-1-amine, formaldehyde and 2,4-dichlorophenol.…”

4-(Ammoniomethyl)benzoate, a protic zwitterionic bifunctional linker in uranyl ion carboxylate complexes

“…This has the disadvantage of eliminating usage of the positively charged centre for strong hydrogen bonding interactions, a factor which can strongly influence the role of a zwitterionic ligand as a structure determinant. [12][13][14][15][16][17][18][19][20][21][22][23] The best known protic zwitterions are the amino acids but the known structural chemistry of their uranyl ion complexes, while showing this importance of ammonium-centre hydrogen bonding, is very limited, involving only glycine, [24][25][26] alanine 25 and proline. 27 This paucity of information is due, in our experience, to reactions, both under solvothermal or mild ambient conditions and in the presence or absence of light, of most amino acids in the presence of uranyl ion which result in their decomposition.…”