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 4phosphoryl pyrazolones, HL 2 -HL 4 , 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 HL 4 compared to the use of the industrially employed acylpyrazolone HL 1 (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 HL 2 -HL 4 represent a new class of ligands that are very effective extractants for use in lithium separation.

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.

In situ electrophilic fluorination of phosphanes with commercially available bench-stable N-fluorobenzenesulfonimide (NFSI), followed by subsequent methylation of the [N(PhSO2)2]- anion with MeOTf yields a family of electrophilic fluorophosphonium cations as...

Reaction of 1,3,4,6-tetra-O-acetyl-N-(2-hydroxy)-naphthylidene glucosamine (HL(Ac)) with uranyl acetate in ethanol leads to formation of dinuclear [(UO2)2(L)2] (1). In a second step 1 is quantitatively transferred into the trinuclear oxo-bridged complex...