Issue 32, 2015

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.

Graphical abstract: Europium, uranyl, and thorium-phenanthroline amide complexes in acetonitrile solution: an ESI-MS and DFT combined investigation

Supplementary files

Article information

Article type
Paper
Submitted
11 May 2015
Accepted
08 Jul 2015
First published
08 Jul 2015

Dalton Trans., 2015,44, 14376-14387

Author version available

Europium, uranyl, and thorium-phenanthroline amide complexes in acetonitrile solution: an ESI-MS and DFT combined investigation

C. Xiao, C. Wang, L. Mei, X. Zhang, N. Wall, Y. Zhao, Z. Chai and W. Shi, Dalton Trans., 2015, 44, 14376 DOI: 10.1039/C5DT01766A

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