The molecular origin of the selectivity of N-donor ligands, such as alkylated bis-triazinyl pyridines (BTPs), for actinide complexation in the presence of lanthanides is still largely unclear. NMR investigations of an Am(nPrBTP)3(3+) complex with a (15)N labelled ligand showed that it exhibits large differences in (15)N chemical shift for coordinating N-atoms in comparison to both lanthanide(III) complexes and the free ligand. The temperature dependence of NMR chemical shifts observed for this complex indicates a weak paramagnetism. This fact and the observed large chemical shift for bound nitrogen atoms allow us to conclude that metal-ligand bonding in the reported Am(III) N-donor complex has a larger share of covalence than in lanthanide complexes. This may account for the observed selectivity.

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NMR investigations of Am(C5-BPP)33+ show weak paramagnetism in Am(iii), indicating significant covalence in metal–ligand bonds with N-donor ligands. This may explain the observed extraction selectivity for actinides over lanthanides.

Two BTP-type N-donor ligands with different numbers of aromatic nitrogen atoms (2,6-bis(4-ethyl-pyridazin-1-yl)pyridine, Et-BDP and 2,6-bis(4-(n)propyl-2,3,5,6-tetrazine-1-yl)pyridine, (n)Pr-Tetrazine) have been synthesized and characterized by NMR and MS techniques. The complexation with Cm(III) in 2-propanol-water (1 : 1, vol.) is studied for both ligands using time resolved laser-induced fluorescence spectroscopy (TRLFS) and the complexation properties are compared to (n)Pr-BTP. With increasing the ligand concentration three different species, the 1 : 1-, 1 : 2- and 1 : 3-complex, were found. Log β3 values of 7.6 for the formation of Cm(Et-BDP)3 and 9.2 for the formation of Cm((n)Pr-Tetrazine)3 are determined. The complexation with (n)Pr-Tetrazine shows slow kinetics. Thermodynamic data of the complexation reactions are determined in a temperature range of 25 °C-60 °C. The complexation with Et-BDP is exothermic (ΔH = -16.3 ± 1.2 kJ mol(-1)) and exergonic (ΔG = -43.8 ± 2.6 kJ mol(-1)) whereas the complexation with (n)Pr-Tetrazine is endothermic (ΔH = 43.9 ± 3.1 kJ mol(-1)) and exergonic (ΔG = -51.7 ± 2.2 kJ mol(-1)). In the case of the latter the complexation is driven by a highly positive reaction entropy change (ΔS = 320.6 ± 15.4 J mol(-1) K(-1)). In comparison to (n)Pr-BTP, less negative ΔG values were found for the complexation of Cm(III) with both ligands.

Di- and tetraphosphines with rigid phenyl-, biphenyl-, and tetraphenylstannane, -silane, and -methane scaffolds, and various substituents R, have been synthesized and immobilized via triethoxysilane-propagated formation of one or two surface-bound phosphonium moieties. The remaining phosphine groups can be coordinated to metal complexes. All the detective work and proof is done by solid-state NMR spectroscopy.

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Breaking down lignin into smaller units is the key to generate high value‐added products. Nevertheless, dissolving this complex plant polyphenol in an environment‐friendly way is often a challenge. Levulinic acid, which is formed during the hydrothermal processing of lignocellulosic biomass, has been shown to efficiently dissolve lignin. Herein, levulinic acid was evaluated as a medium for the reductive electrochemical depolymerization of the lignin macromolecule. Copper was chosen as the electrocatalyst due to the economic feasibility and low activity towards the hydrogen evolution reaction. After depolymerization, high‐resolution mass spectrometry and nuclear magnetic resonance spectroscopy revealed lignin‐derived monomers and dimers. A predominance of aryl ether and phenolic groups was observed. Depolymerized lignin was further evaluated as an anti‐corrosion coating, revealing enhancements on the electrochemical stability of the metal. Via a simple depolymerization process of biomass waste in a biomass‐based solvent, a straightforward approach to produce high value‐added compounds or tailored biobased materials was demonstrated.

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