title: Europium, uranyl, and thorium-phenanthroline amide complexes in acetonitrile solution: an ESI-MS and DFT combined investigation.
abstract: The tetradentate N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) ligand with hard-soft donor atoms has been demonstrated to be promising for the group separation of actinides from highly acidic nuclear wastes. To identify the formed complexes of this ligand with actinides and lanthanides, electrospray ionization mass spectrometry (ESI-MS) combined with density functional theory (DFT) calculations was used to probe the possible complexation processes. The 1 : 2 Eu-L species ([EuL2(NO3)](2+)) can be observed in ESI-MS at low metal-to-ligand ([M]/[L]) ratios, whereas the 1 : 1 Eu-L species ([EuL(NO3)2](+)) can be observed when the [M]/[L] ratio is higher than 1.0. However, ([UO2L(NO3)](+)) is the only detected species for the uranyl complexes. The [ThL2(NO3)2](2+) species can be observed at low [M]/[L] ratios; the 1 : 2 species ([ThL2(NO3)](3+)) and a new 1 : 1 species ([ThL(NO3)3](+)) can be detected at high [M]/[L] ratios. Collision-induced dissociation (CID) results showed that Et-Tol-DAPhen ligands can coordinate strongly with metal ions, and the coordination moieties remain intact under CID conditions. Natural bond orbital (NBO), molecular electrostatic potential (MEP), electron localization function (ELF), atoms in molecules (AIM) and molecular orbital (MO) analyses indicated that the metal-ligand bonds of the actinide complexes exhibited more covalent character than those of the lanthanide complexes. In addition, according to thermodynamic analysis, the stable cationic M-L complexes in acetonitrile are found to be in good agreement with the ESI-MS results.
authors.affiliation: School for Radiological and Interdisciplinary Sciences (RAD-X) and Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China.
authors.forename: Cheng-Liang
authors.initials: CL
authors.lastname: Xiao
authors.forename: Cong-Zhi
authors.initials: CZ
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Mei
authors.forename: Xin-Rui
authors.initials: XR
authors.lastname: Zhang
authors.forename: Nathalie
authors.initials: N
authors.lastname: Wall
authors.forename: Yu-Liang
authors.initials: YL
authors.lastname: Zhao
authors.forename: Zhi-Fang
authors.initials: ZF
authors.lastname: Chai
authors.forename: Wei-Qun
authors.initials: WQ
authors.lastname: Shi
mesh_terms: D000097:Acetonitriles / Q000737:chemistry*; D000577:Amides / Q000737:chemistry*; D005063:Europium / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D010618:Phenanthrolines / Q000737:chemistry*; D011789:Quantum Theory; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013816:Thermodynamics; D013910:Thorium / Q000737:chemistry*; D014501:Uranium / Q000737:chemistry*
chemical_list: D000097:Acetonitriles; D000577:Amides; D009942:Organometallic Compounds; D010618:Phenanthrolines; D005063:Europium; D014501:Uranium; D013910:Thorium; C025205:1,10-phenanthroline; C032159:acetonitrile