2,6-Bis(5-(2,2-dimethylpropyl)-1<i>H</i>-pyrazol-3-yl)pyridine as a Ligand for Efficient Actinide(III)/Lanthanide(III) Separation

The N-donor complexing ligand 2,6-bis­(5-(2,2-dimethylpropyl)-1<i>H</i>-pyrazol-3-yl)­pyridine (C5-BPP) was synthesized and screened as an extracting agent selective for trivalent actinide cations over lanthanides. C5-BPP extracts Am­(III) from up to 1 mol/L HNO₃ with a separation factor over Eu­(III) of approximately 100. Due to its good performance as an extracting agent, the complexation of trivalent actinides and lanthanides with C5-BPP was studied. The solid-state compounds [Ln­(C5-BPP)­(NO₃)₃(DMF)] (Ln = Sm­(III), Eu­(III)) were synthesized, fully characterized, and compared to the solution structure of the Am­(III) 1:1 complex [Am­(C5-BPP)­(NO₃)₃]. The high stability constant of log β₃ = 14.8 ± 0.4 determined for the Cm­(III) 1:3 complex is in line with C5-BPP’s high distribution ratios for Am­(III) observed in extraction experiments