Neptunium(V) Isothiocyanate Complexes with 4′-Aryl-Substituted 2,2′:6′,2-Terpyridines and N,N-Dimethylacetamide as Molecular Ligands

New complexes of neptunyl(V) isothiocyanate with 4'-aryl-substituted 2,2':6',2 ''-terpyridines (Terpy) and N,N-dimethylacetamide (DMA) were obtained: [(NpO2)(4'-Ph-Terpy)(DMA)(NCS)]center dot DMA, [(NpO2)(4'-(4-(CF3)C6H4)-Terpy)(DMA)(NCS)]center dot 2H(2)O center dot DMA, [(NpO2)(4'-(3-BrC6H4)-Terpy)(DMA)(NCS)]center dot DMA, and [(NpO2)(4'-(2-(COOH)C6H4)Terpy)(DMA)(NCS)]center dot DMA. The structures of the compounds were determined with X-ray diffraction analysis. The neptunium coordination polyhedra were found to be pentagonal bipyramids with O atoms of the NpO2 groups in the apical positions and the equatorial planes formed by three N atoms of the terpyridine ligand, a N atom of the isothiocyanate anion, and an O atom of DMA. The influence of the substituents of the Ar group on the crystal structure is discussed. The IR spectra contain well-resolved bands of characteristic vibrations of all groups in the complex. The electronic absorption spectra are typical for neptunium(V) complexes and contain an intense narrow absorption band belonging to an f-f transition with a maximum of 988 nm and several long-wave satellites of lower intensity. The substituted terpyridines were shown to be efficient for the extraction of various valence forms of neptunium from the isothiocyanate solutions.

Automated summary

New complexes of neptunyl(V) isothiocyanate with 4'-aryl-substituted 2,2':6',2 ''-terpyridines and N,N-dimethylacetamide were obtained and their structures were determined by X-ray diffraction analysis. The neptunium coordination polyhedra were found to be pentagonal bipyramids. The substituted terpyridines were shown to be efficient for the extraction of various valence forms of neptunium from the isothiocyanate solutions.