Exploring electronic effects on the partitioning of actinides(iii) from lanthanides(iii) using functionalised bis-triazinyl phenanthroline ligands

Alyn C Edwards; Christoph Wagner; Andreas Geist; Neil A Burton; Clint A Sharrad; Ralph W Adams; Robin G Pritchard; Petra J Panak; Roger C Whitehead; Laurence M Harwood

doi:10.1039/c6dt02474b

Exploring electronic effects on the partitioning of actinides(iii) from lanthanides(iii) using functionalised bis-triazinyl phenanthroline ligands

Dalton Trans. 2016 Nov 15;45(45):18102-18112. doi: 10.1039/c6dt02474b.

Affiliations

¹ School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK. roger.whitehead@manchester.ac.uk.
² Karlsruher Institut für Technologie (KIT-INE), Institut für Nukleare Entsorgung, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany and University of Heidelberg, Department of Physical Chemistry, Im Neuenheimer Feld 253, 69120, Germany.
³ Karlsruher Institut für Technologie (KIT-INE), Institut für Nukleare Entsorgung, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.
⁴ School of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
⁵ Department of Chemistry, The University of Reading, Reading, RG6 6AD, UK. l.m.harwood@reading.ac.uk.

PMID: 27488559
DOI: 10.1039/c6dt02474b

Abstract

The first examples of 4,7-disubstituted 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzo-triazin-3-yl)-1,10-phenanthroline (CyMe₄-BTPhen) ligands are reported herein. Evaluating the kinetics, selectivity and stoichiometry of actinide(iii) and lanthanide(iii) radiotracer extractions has provided a mechanistic insight into the extraction process. For the first time, it has been demonstrated that metal ion extraction kinetics can be modulated by backbone functionalisation and a promising new CHON compliant candidate ligand with enhanced metal ion extraction kinetics has been identified. The effects of 4,7-functionalisation on the equilibrium metal ion distribution ratios are far more pronounced than those of 5,6-functionalisation. The complexation of Cm(iii) with two of the functionalised ligands was investigated by TRLFS and, at equilibrium, species of 1 : 2 [M : L] stoichiometry were observed exclusively. A direct correlation between the E_LUMO-E_HOMO energy gap and metal ion extraction potential is reported, with DFT studies reaffirming experimental findings.