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Effective receptors for the separation of Li+ from a mixture with other alkali metal ions under mild conditions remains an important challenge that could benefit from new approaches. In this study, it is demonstrated that the 4‐phosphoryl pyrazolones, HL2‐HL4, in the presence of the typical industrial organophosphorus co‐ligands tributylphosphine oxide (TBPO), tributylphosphate (TBP) and trioctylphosphine oxide (TOPO), are able to selectively recognise and extract lithium ions from aqueous solution. Structural investigations in solution as well as in the solid state reveal the existence of a series of multinuclear Li+ complexes that include dimers (TBPO, TBP) as well as rarely observed trimers (TOPO) and represent the first clear evidence for the synergistic role of the co‐ligands in the extraction process. Our findings are supported by detailed NMR, MS and extraction studies. Liquid‐liquid extraction in the presence of TOPO revealed an unprecedented high Li+ extraction efficiency (78 %) for HL4 compared to the use of the industrially employed acylpyrazolone HL1 (15 %) and benzoyl‐1,1,1‐trifluoroacetone (52 %) extractants. In addition, a high selectivity for Li+ over Na+, K+ and Cs+ under mild conditions (pH ∼8.2) confirms that HL2‐HL4 represent a new class of ligands that are very effective extractants for use in lithium separation. [ABSTRACT FROM AUTHOR]

Recent advances in guanidinium-based receptors are summarized emphasizing the high affinity of the guanidinium moiety towards certain anions in highly competitive aqueous media. Particularly the interaction with multivalent oxoanions such as phosphate, sulfate, chromate, or even pertechnetate is of great interest for recognition. This review summarizes additionally selected developments in guanidine synthesis that are the basis of guanidinium based receptors and functionalized materials with an advanced recognition of certain anions under interfacial aqueous condition. [ABSTRACT FROM AUTHOR]

We prepared acetic acid derivatives using three different frameworks, calix[4]arene, alkenyltrimethylol, and trihydroxytriphenylmethane, which differ in the number and size of their coordination sites. We further investigated the extraction properties for aluminum group metal ions. All three extraction reagents exhibited increased extraction compared with the corresponding monomeric compounds, owing to structural effects. The extraction reaction and extraction equilibrium constants were determined using a slope analysis. Their extraction abilities, separation efficiencies, and potential coordination modes are discussed using the extraction equilibrium constants, half-pH values, and spectroscopic data. The calix[4]arene and trihydroxytriphenylmethane derivatives demonstrated allosteric co-extraction of indium ions (In3+) with an unexpected stoichiometry of 1:2. [ABSTRACT FROM AUTHOR]

The reaction of UO2(OAc)2 ⋅ 2H2O with the biologically inspired ligand 2‐salicylidene glucosamine (H2L1) results in the formation of the anionic trinuclear uranyl complex [(UO2)3(μ3‐O)(L1)3]2− (12−), which was isolated in good yield as its Cs‐salt, [Cs]21. Recrystallization of [Cs]21 in the presence of 18‐crown‐6 led to formation of a neutral ion pair of type [M(18‐crown‐6)]21, which was also obtained for the alkali metal ions Rb+ and K+ (M=Cs, Rb, K). The related ligand, 2‐(2‐hydroxy‐1‐naphthylidene) glucosamine (H2L2) in a similar procedure with Cs+ gave the corresponding complex [Cs(18‐crown‐6)]2[(UO2)3(μ3‐O)(L2)3 ([Cs(18‐crown‐6)]22). From X‐ray investigations, the [(UO2)3O(Ln)3]2− anion (n=1, 2) in each complex is a discrete trinuclear uranyl species that coordinates to the alkali metal ion via three uranyl oxygen atoms. The coordination behavior of H2L1 and H2L2 towards UO22+ was investigated by NMR, UV/Vis spectroscopy and mass spectrometry, revealing the in situ formation of the 12− and 22−dianions in solution. [ABSTRACT FROM AUTHOR]

Two new mixed aza-thia crowns 5-aza-2,8-dithia[9]-(2,9)-1,10-phenanthrolinophane and 2,8-diaza-5-thia[9]-(2,9)-1,10-phenanthrolinophane are prepared and analyzed. The efficacy of these systems in competitive liquid-liquid metal ion extraction of [Cu.sup.II], [Zn.sup.II], [Cd.sup.II], [Pb.sup.II], [Ag.sup.I] and [Hg.sup.II] is assessed and it is shown that clear extraction selectivity for [Ag.sup.I] is seen in the absence of [Hg.sup.II].

Extraction experiments of a series of tris(2-aminoethyl)amine-based ligands with different aromatic substituents act as efficient extractants for transition metals. Octanol-water distribution measurements, determined stability constants of Ag(I) complexes and Zn(II) extraction studies with different counterions point to the extraction efficiency in dependence of the ligand lipophilicity and the specific structure of the ligand. Competitive extraction experiments showed a selective extraction of Cu(II) from a mixture of Co(II), Ni(II), Cu(II), Zn(II), and Cd(II). Additional hydroxyl groups in (tris(2-hydroxybenzylaminoethyl)amine lead to a loss of this selectivity with extraction yields of 46%, 86% and 97% for Co(II), Ni(II) and Cd(II) ions. [ABSTRACT FROM AUTHOR]