Activation of the Aromatic Core of 3,3'-(Pyridine-2,6-diylbis(1 H-1,2,3-triazole-4,1-diyl))bis(propan-1-ol)-Effects on Extraction Performance, Stability Constants, and Basicity

Patrik Weßling; Michael Trumm; Elena Macerata; Annalisa Ossola; Eros Mossini; Maria Chiara Gullo; Arturo Arduini; Alessandro Casnati; Mario Mariani; Christian Adam; Andreas Geist; Petra J Panak

doi:10.1021/acs.inorgchem.9b02325

Activation of the Aromatic Core of 3,3'-(Pyridine-2,6-diylbis(1 H-1,2,3-triazole-4,1-diyl))bis(propan-1-ol)-Effects on Extraction Performance, Stability Constants, and Basicity

Inorg Chem. 2019 Nov 4;58(21):14642-14651. doi: 10.1021/acs.inorgchem.9b02325. Epub 2019 Oct 14.

Authors

Affiliations

¹ Institute for Nuclear Waste Disposal , Karlsruhe Institute of Technology , P.O. Box 3640, 76021 Karlsruhe , Germany.
² Institut für Physikalische Chemie , Ruprecht-Karls-Universität Heidelberg , Im Neuenheimer Feld 253 , 69120 Heidelberg , Germany.
³ Politecnico di Milano, Department of Energy , Nuclear Engineering Division , Piazza Leonardo da Vinci 32 , 20133 Milano , Italy.
⁴ Dipartimento di Scienze Chimiche, della Vita e della Sostenibilitá Ambientale , Universitá di Parma , Area delle Scienze 17/a , 43124 Parma , Italy.

Abstract

The "CHON" compatible water-soluble ligand 3,3'-(pyridine-2,6-diylbis(1H-1,2,3-triazole-4,1-diyl))bis(propan-1-ol) (PTD) has shown promise for selectively stripping actinide ions from an organic phase containing both actinide and lanthanide ions, by preferential complexation of the former. Aiming at improving its complexation properties, PTD-OMe was synthesized, bearing a methoxy group on the central pyridine ring, thus increasing its basicity and hence complexation strength. Unfortunately, solvent extraction experiments in the range of 0.1-1 mol/L nitric acid proved PTD-OMe to be less efficient than PTD. This behavior is explained by its greater pK_a value (pK_a = 2.54) compared to PTD (pK_a = 2.1). This counteracts its improved complexation properties for Cm(III) (log β₃(PTD-OMe) = 10.8 ± 0.4 versus log β₃(PTD) = 9.9 ± 0.5).