Insights into Potassium 18-Crown-6 Complexes with Pertechnetate and Perrhenate: A Structural and Computational Study of their Coordination Chemistry

Abstract

The synthesis, crystal structures, and characterization of potassium 18-crown-6 complexes with tetrahedral oxoanions, [K(18-crown-6)][XO4] (X = Tc, Re), are reported. X-ray diffraction analysis shows that K−O interactions between the potassium ion and the OTcO3− or OReO3− groups extend the discrete molecular units into 1D supramolecular assemblies. Additionally, CHO interactions between the methylene groups of 18-crown-6 and the oxoanions contribute to the stabilization of the solid-state structures. These assemblies and the strengths of their interactions were further analyzed using density functional theory calculations, including molecular electrostatic potential (ESP) surfaces and the quantum theory of atoms in molecules (QTAIM). The stability of the KO interactions supports the potential of crown ethers for selective extraction of pertechnetate species from nuclear waste.