An Insight into the Complexation of Pyrazine- Functionalized Calix[4]arenes with Am~(3+) and Eu~(3+) - Solvent Extraction and Luminescence Studies in Room-Temperature Ionic Liquids

摘要

The complexation behaviour of six pyrazine-functionalized calix[4]arenes, containing substituents such as carbamoyl dioctyl (L-1, L-2), diisopropyl phosphonate (L-3, L-4) and diphenyl phosphoryl (L-5, L-6), with Am~(3+) and Eu~(3+) ions was investigated by solvent extraction as well as by luminescence spectroscopy (only for Eu~(3+)) in room-temperature ionic liquids (RTILs), [C_nmim][NTf_2] (1-alkyl-3-methylimidazolium, n = 4, 6, and 8). The spectacular enhancement in the extraction values of the trivalent metal ions in RTILs, as compared to those reported in a molecular diluent from 3 M HNO_3, was rather unusual and was further investigated by luminescence studies. Luminescence studies involving Eu~(3+) and performed with L-4 and L-6 confirmed the 1:1 stoichiometry of the extracted species (Eu~(3+) L) with log β values of 4.42±0.51 and 5.18±0.38 for L-4 and L-6, respectively. Judd-Ofelt parameters, which give information about the nature of bonding as well as the coordinating environment, were computed from the emission spectra of the Eu~(3+) L-4 and Eu~(3+)L-6 complexes.