Two series of polydentate N,O,S-ligands containing thiourea fragments attached to a p-cresol scaffold, unsymmetrical mono-acylated bis-amines and symmetrical bis-thioureas, are obtained by common experiments. It is observed that the reaction output is strongly dependent on both bis-amine and thiocarbamic chloride substituents. The products are characterized by 1D and 2D NMR spectra in solution and by single crystal XRD. A preliminary study on the coordination abilities of selected products is performed by ITC at around neutral media.

A new solvent extraction system for the removal of 4f ions (Ln³⁺) from water by use of chelating ligands (HLn, n = 5, 6, 7, and 8) composed of heterocyclic receptors and one β-dicarbonyl fragment is reported. The covalent attachment of a β-dicarbonyl unit to a saturated N-heterocycle with variable ring size resulted in a cooperative interaction within the receptor for Ln³⁺ transfer, which remarkably enhanced the efficiency of the process. The intramolecular cooperative effect was observed only in the ionic liquid (IL) solvent system, providing a several-fold increase in extraction performance for Ln³⁺ ions (La, Nd, Eu and Dy) over chloroform. Thus, it is not possible to confirm that an identical reaction mechanism operated in both liquid systems: IL or CHCl₃. The existence of neutral chelates of the type LnL₃ or anionic lanthanoid complexes [LnL₄⁻] in an ionic medium during the solvent extraction process applying various solvent systems has been established hitherto. Consequently, the Ln³⁺ ion was held by HLn molecules more rigidly in an IL medium ([C₁C_nim⁺]/[C₁C₄pyr⁺]/[C₁C₄pip⁺][Tf₂N⁻], n = 4, 6, 8, 10) than in chloroform, representing an important factor dominating the magnitude of the intramolecular cooperative effect of the chelating ligands for Ln³⁺ ions. The effect of the diluent’s chemical nature on the metal extraction and separation has been studied and discussed thoroughly. Furthermore, competitive solvent extraction and separation studies with various s-, p-, d-, and f-ions of the periodic table revealed that the magnitude of the intramolecular cooperative effect depends on the suitability between the metal ion size and the cavity size or flexibility of the HLn compounds. In addition, the solvent extraction process of 12 refractory metals and 8 platinum group metals with the synthesized chelating extractants is also investigated in different organic liquid media.

In this study, three series of polydentate N,O-ligands possessing unsymmetrical urea fragments attached to a p-cresol scaffold are obtained, namely mono- and bi-substituted open-chain aromatics, synthesised using a common experiment, as well as fused aryloxazinones. Separate protocols for the preparation of each series are developed. It is found that in the case of open-chain compounds, the reaction output is strongly dependent on both bis-amine and carbamoyl chloride substituents, while oxazinones can be effectively obtained via a common protocol. The products are characterized via 1D and 2D NMR spectra in solution and using single-crystal XRD. A preliminary study on the coordination abilities of the products performed via ITC shows that there are no substantial interactions in the pH range of 5.0–8.5 in general.

This competitive solvent extraction study of various metal species (27) in the periodic table was conducted by using a series of asymmetric ligands, tested for the first time, composed of N-heterocyclic receptors with variable ring size and a β-dicarbonyl fragment with the aim of providing a snapshot of their efficacy. We evaluated the effect of heteroatoms in the substituent on solvent extraction performance and the selectivity of this type of chelating extractant with equivalent binding sites but an unsymmetric backbone due to differing coordination environments. The influence of the chemical nature of the organic liquid phase on the solvent extraction process was also discussed: ionic liquids ([C₁C_nim⁺][Tf₂N⁻]) or typical organic diluents. Fe³⁺ can be extracted with all ligands only in IL medium (100%). The separation factors (SFs) between adjacent metals of 4f-series and iron towards other s-, p, d- and f-block metal ions have been assessed from a circular economy perspective: to extend the product lifecycle and regenerate natural resources. The SF values (Fe/Lns) were below ca. 6 for CHCl₃, while the SFs for adjacent 4f-series ions were generally close to 1.1, with higher selectivity observed for selected ion pairs. In addition, the competitive solvent extraction process of 12 refractory metals as well as 8 platinum group metals was investigated with the synthesized ligands. The diluent n-heptane (a structurally symmetric alkane) outperformed isooctane (an asymmetric branched alkane) and chloroform (a polar asymmetric solvent) for refractory metal recovery with a maximum efficiency (100%). Furthermore, EPR, Raman and DTA-TG-MS spectroscopy analyses were used to study the extracted d- and f-chelate complexes in the ionic liquid media: Gd³⁺, Cu²⁺ and Fe³⁺.