title: Selective Extraction of Americium(III) over Europium(III) with the Pyridylpyrazole Based Tetradentate Ligands: Experimental and Theoretical Study.
abstract: 1,3-Bis[3-(2-pyridyl)pyrazol-1-yl]propane (Bippp) and 1,2-bis[3-(2-pyridyl)pyrazyl-1-methyl]benzene (Dbnpp), the pyridylpyrazole based tetradentate ligands, were synthesized and characterized by MS, NMR, and FT-IR. The solvent extraction and complexation behaviors of Am(III) and Eu(III) with the ligands were investigated experimentally and theoretically. In the presence of 2-bromohexanoic acid, the two ligands can effectively extract Am(III) over Eu(III) and other rare earth(III) metals (RE(III)) in HNO3 solution with the separation factors (SFAm/RE) ranging from 15 to 60. Slope analyses showed that both Am(III) and Eu(III) were extracted as monosolvated species, which agrees well with the results observed from X-ray crystallography and MS analyses. The stability constants (log K) obtained from UV-vis titration for Eu(III) complexes with Bippp and Dbnpp are 4.75 ± 0.03 and 4.45 ± 0.04, respectively. Both UV-vis titration and solvent extraction studies indicated that Bippp had stronger affinity for Eu(III) than Dbnpp, which is confirmed by density functional theory (DFT) calculations. DFT calculations revealed that the AmL(NO3)3 (L = Bippp and Dbnpp) complexes are thermodynamically more stable in water than their Eu(III) analogues, which is caused by greater covalency of the Am-N than Eu-N bonds. Theoretical studies gave an insight into the nature of the M(III)-ligand bonding interactions.
authors.affiliation: College of Chemistry, Sichuan University , Chengdu 610064, P.R. China.
authors.forename: Jieru
authors.initials: J
authors.lastname: Wang
authors.affiliation: College of Chemistry, Sichuan University , Chengdu 610064, P.R. China.
authors.forename: Dongping
authors.initials: D
authors.lastname: Su
authors.affiliation: Multidisciplinary Initiative Center, Institute of High Energy Physics, Chinese Academy of Sciences , Beijing 100049, P.R. China.
authors.forename: Dongqi
authors.initials: D
authors.lastname: Wang
authors.affiliation: College of Chemistry, Sichuan University , Chengdu 610064, P.R. China.
authors.forename: Songdong
authors.initials: S
authors.lastname: Ding
authors.affiliation: College of Chemistry, Sichuan University , Chengdu 610064, P.R. China.
authors.forename: Chao
authors.initials: C
authors.lastname: Huang
authors.affiliation: College of Chemistry, Sichuan University , Chengdu 610064, P.R. China.
authors.forename: Huang
authors.initials: H
authors.lastname: Huang
authors.affiliation: College of Chemistry, Sichuan University , Chengdu 610064, P.R. China.
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Hu
authors.affiliation: College of Chemistry, Sichuan University , Chengdu 610064, P.R. China.
authors.forename: Zhipeng
authors.initials: Z
authors.lastname: Wang
authors.affiliation: College of Chemistry, Sichuan University , Chengdu 610064, P.R. China.
authors.forename: Shimeng
authors.initials: S
authors.lastname: Li