Synthesis, selected coordination chemistry and extraction behavior of a (phosphinoylmethyl)pyridyl N-oxide-functionalized ligand based upon a 1,4-diazepane platform

Syntheses for the new multidentate chelating ligands ((6,6′-((1,4-diazepane-1,4-diyl)bis(methylene))bis(pyridine-6,2-diyl))bis(methylene))bis(diphenylphosphine oxide) (2) and 6,6′-((1,4-diazepane-1,4-diyl)bis(methylene))bis(2-((diphenylphosphoryl)methyl)pyridine 1-oxide) (3), based upon a 1,4-diazepane platform functionalized with 2-(diphenylphosphinoylmethyl)pyridine P-oxide and 2-(diphenylphosphinoylmethyl)pyridine N,P-dioxide fragments, respectively, are reported. Results from studies of the coordination chemistry of the ligands with selected lanthanide nitrates and Cu(BF4)2 are outlined, and crystal structures for two complexes, [Cu(2)](BF4)2 and [Cu(3)](BF4)2, are described along with survey Eu(III) and Am(III) solvent extraction analysis, for 3.

Graphical abstractNew pre-organized, hexadentate chelating phosphinoylmethyl pyridine and –pyridine N-oxide ligands, based upon a 1,4-diazepane platform, form stable complexes with Ln(III) and Cu(II) ions. Solvent extraction analyses for Eu(III) and Am(III) in nitric acid with the pyridine N-oxide derivative show improved performance, at the highest nitric acid concentrations, compared to the parent bidentate phosphinoylmethyl pyridine N-oxide ligand.Figure optionsDownload full-size imageDownload as PowerPoint slide