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Bis(2-propyloxy)calix[4]arene-crown-6 ( L1 ) is a ligand with high affinity in the extraction of Cs(I). In this work, acrylamido and propionamido groups are decorated at the opposite site of 2-propyloxy on the phenyl ring of L1 , giving rise to the derivatives L2 and L3 , respectively. Complexation of all the three ligands with Cs(I) is characterized by NMR, spectrophotometric titration, crystal structure and DFT calculation. Both the NMR and spectrophotometric analysis suggest more significant variation of electron density on the phenyl rings in L2 and L3 than that in L1 in complexation with Cs(I). The stability constants (log β ) of the complexes are calculated to be 6.0 ± 0.1, 6.2 ± 0.1 and 6.3 ± 0.1 for Cs- L1 , Cs- L2 and Cs- L3 , respectively, by fitting of the absorption spectra. As reflected by the crystal structures and DFT calculations, the complexed cesium cation interacts with the crown ether moiety, the two rotated phenyl rings and the acrylamido/propionamido groups in L2 / L3 , which can be regarded as an intramolecular triple cooperative effect. Extraction of Cs(I) from aqueous solution is performed, and the distribution ratio is in line with the findings in stability constant and interaction energy. This work contributes to further improvement of the extraction of cesium cation by 1,3-alternate calix[4]arene-crown-6. [ABSTRACT FROM AUTHOR]

Bis(trifluoromethylsulfonyl)imide (NTf 2 − ) and hexafluorophosphate (PF 6 − ) are the most frequently used anions for hydrophobic ionic liquids (ILs) which have been considered as promising solvents in the extraction of cesium ions. The interactions of NTf 2 − and PF 6 − with Cs + were explored in this work. The results of DFT calculation indicated that both Cs + and Cs(18C6) + prefer to interact with two NTf 2 − or PF 6 − anions in gas phase, where 18C6 is 18-crown-6. The complex of Cs(NTf 2 ) 2 − was observed in electrospray ionization mass spectrometry (ESI-MS), and the complexes of [Cs(18C6)NTf 2 ] 2 and [Cs(18C6)PF 6 ] 2 were crystallized in which Cs(18C6) + interacted with two anions. The interactions of NTf 2 − with cesium resulted in a synergistic effect between dicyclohexano-18-crown-6 (DCH18C6) and NTf 2 − in the extraction of Cs + using n -octanol as diluent. However, DFT calculation revealed that the complex Cs(DCH18C6) + interacted with one NTf 2 − anion was more thermodynamically stable than that with two anions in organic phase, different from that in gas phase. [ABSTRACT FROM AUTHOR]