Extraction and complexation of americium(III) and europium(III) by a N-donor ligand of 3,5-bis(2-pyridyl)pyrazole

The synthesis, Eu 3+ complexation, and selective solvent extraction of trivalent americium (Am 3+ ) over trivalent europium (Eu 3+ ) in nitric acid solution by N-donor ligand of 3,5-bis(2-pyridyl)pyrazole (BisPypzH) were described. By using tert -butyl benzene as diluent, BisPypzH ligand in combination with 2-bromohexanoic acid demonstrated the extraction selectivity for Am 3+ over trivalent lanthanides (Ln 3+ ) with the separation factor ( SF Am/Ln ) value ranging from 14.3 to 59.4. Slope analysis showed the formation of 1:1 and 1:2 metal/ligand extracted species corresponding to the BisPypzH concentration below and above 0.025 mol/L, respectively, which was also confirmed by electrospray ionization mass spectrometry (ESI-MS) and dynamic light scattering (DLS) analyses. The extraction conformed to a cation-exchange model. Additionally, the 1:1 and 1:2 metal/ligand complexes were also observed in methanol solution and in solid state, severally, by means of UV–vis spectroscopy, luminescence spectroscopy and ESI-MS. Furthermore, the analyses of Fourier transform infrared spectra (FTIR), Raman spectra, and time-resolved laser-induced fluorescence spectra (TRLFS) indicated the presence of three bidentate NO 3 − and the absence of H 2 O molecules in the inner coordination sphere of the central Eu cation in the complex. Meanwhile, the stability constant for BisPypzH-Eu complex was also given.