This review describes the latest advances regarding the development, modification and application of suitable ligands for the liquid–liquid extraction of actinides and lanthanides from nuclear waste.

An N-pivot diglycolamide extractant (DGA-TREN) was synthesized for the first time and its complexation behaviour was studied towards trivalent lanthanide/actinide ions. The solvent extraction studies suggested a unique selectivity reversal in the extraction of trivalent actinides versus trivalent lanthanides which was observed performing extraction studies in an ionic liquid vis-à-vis a molecular diluent for a tripodal TREN-based diglycolamide ligand (DGA-TREN) vs. a tripodal diglycolamide ligand (T-DGA) which may have great significance in radioactive waste remediation. The nature of the bonding to Eu³⁺ ion was investigated by EXAFS as well as by DFT calculations.

The stability against gamma radiation of MeTODGA (methyl tetraoctyldiglycolamide) and Me₂TODGA (dimethyl tetraoctyldiglycolamide), derivatives from the well-known extractant TODGA (N,N,N′,N′-tetraoctyldiglycolamide), were studied and compared. Solutions of MeTODGA and Me₂TODGA in alkane diluents were subjected to ⁶⁰Co γ-irradiation in the presence and absence of nitric acid and analyzed using LC-MS to determine their rates of radiolytic concentration decrease, as well as to identify radiolysis products. The results of product identification from three different laboratories are compared and found to be in good agreement. The diglycolamide (DGA) concentrations decreased exponentially with increasing absorbed dose. The MeTODGA degradation rate constants (dose constants) were uninfluenced by the presence of nitric acid, but the acid increased the rate of degradation for Me₂TODGA. The degradation products formed by irradiation are also initially produced in greater amounts in acid-contacted solution, but products may also be degraded by continued radiolysis. The identified radiolysis products suggest that the weakest bonds are those in the diglycolamide center of these molecules.

Three benzene-centered tripodal diglycolamides (Bz-T-DGAs) were synthesized and evaluated for actinide, lanthanide, and fission product ion extraction. 1,3,5-Triethylbenzene-based tripodal DGA (L_I) showed high distribution ratio (D) values for Am³⁺ and Eu³⁺ in a mixture of 95% n-dodecane and 5% iso-decanol at 3 M HNO₃. Eu/Am separation factors, in the range of 8–10, were obtained at 1 M HNO₃ which decreased at higher acidities with the exception of L_II which did not show much change. Benzene-1,3,5-triamide-based tripodal DGA (L_II) exhibited a high D-value for Pu⁴⁺ compared to the other ligands. Slope analysis showed the formation of 1 : 1 or 1 : 2 complexes is dependent on the ligand. The nature of the complexes was further studied with luminescence spectroscopy (Eu complexes) and DFT calculations (Am complexes).

To develop new types of dynamic molecular devices with atomic-scale control over electronic function, new types of molecular switches are needed with time-dependent switching probabilities. We report such a molecular switch based on proton-coupled electron transfer (PCET) reaction with giant hysteric negative differential resistance (NDR) with peak-to-valley ratios of 120 ± 6.6 and memory on/off ratios of (2.4 ± 0.6) × 10³. The switching dynamics probabilities are modulated by bias voltage sweep rate and can also be controlled by pH and relative humidity, confirmed by kinetic isotope effect measurements. The demonstrated dynamical and environment-specific modulation of giant NDR and memory effects provide new opportunities for bioelectronics and artificial neural networks.