Silver(I) and Thioether-bis(pyrazolyl)methane Ligands: The Correlation between Ligand Functionalization and Coordination Polymer Architecture

This work examines the crystal structures of 15 Ag­(I) complexes with thioether functionalized bis­(pyrazolyl)­methane derivatives to rationalize the influence of the ligand on the formation of (a) coordination polymers (CPs), (b) oligonuclear (hexameric and dinuclear) complexes, and (c) mononuclear complexes. It was previously reported how this ligand class could generate microporous architectures with permanent porosity. Some ligand modifications could induce a cavity size modulation while preserving the same overall architecture. The bis­(pyrazolyl)­methane scaffold can be easily functionalized with various structural fragments; hence the structural outcomes were studied in this work using various ligand modifications and Ag­(I) salts. In particular, six new ligand classes were prepared with the following features: (1) The steric hindrance on the pyrazole rings L^3,3′Me, L^5,5′Me, L^5,3′Me, L^CF3, and L^Br was modified. (2) The steric hindrance was reduced on the peripheral thioether group: L^SMe. (3) Finally, the presence of fluorine and bromine atoms in L^CF3 and L^Br offered the possibility to expand the type of interaction with respect to the ligands based on hydrocarbon substituents (CH₃, phenyl, naphthyl). The effect of the anions was explored using different Ag­(I) precursors such as AgPF₆, AgBF₄, AgCF₃SO₃, or AgNO₃. A comparison of the crystal structures allowed for the tentative identification of the type of substituents able to induce the formation of CPs having permanent porosity to include a symmetric and moderate steric hindrance on the pyrazolyl moieties (four CH₃) and an aromatic and preorganized thioether moiety. An asymmetric steric hindrance on the pyrazole groups led to the formation of more varied structural types. Overall, the most frequently reported structural motifs are the porous hexameric systems and the molecular chains

Actinide–lanthanide co-extraction by rigidified diglycolamides

<p>Within the actinide and lanthanide co-extraction strategy, three rigidified diglycolamides, namely 2,6-bis (<i>N</i>-dodecyl-carboxamide)-4-oxo-4<i>H</i>-pyran (<b>1</b>), 2,6-bis-[<i>N</i>-(4-<i>tert</i>-butylphenyl)carboxamide]-4-oxo-4<i>H</i>-pyran (<b>2</b>), 2,6-​bis[(<i>N</i>-docecyl-<i>N</i>-methyl)carboxamide]-​4-methoxy-​tetrahydro-pyran (<b>3</b>), were synthesized. Moreover, the effect of structural rigidification on Am(III) and Eu(III) extraction under different conditions was investigated. The carboxamide extractant <b>3</b> resembles the extracting behavior of <i>N,N,N</i>′,<i>N</i>′‐tetraoctyl diglycolamide (TODGA) in terms of efficiency and affinity within the lanthanide family, together with fast kinetics and satisfactory cation back-extraction. The presence of 1-octanol in the diluent mixture strongly affects the ligand stability. Moreover, despite the low extraction efficiency showed by <b>1</b> and <b>2</b>, all the three ligands exhibit a higher affinity for Am with respect to TODGA, resulting in a lower lanthanide/Americium separation factor, of around 4 for ligand <b>3</b> and close to 1 for ligands <b>1</b> and <b>2</b>.</p