Extraction and coordination studies of a carbonyl-phosphine oxide scorpionate ligand with uranyl and lanthanide(III) nitrates: structural, spectroscopic and DFT characterization of the complexes

Hybrid scorpionate ligand (OPPh2)(2)CHCH2C(O) Me (L) was synthesized and characterized by spectroscopic methods and X-ray diffraction. The selected coordination chemistry of L with UO2(NO3)(2) and Ln(NO3)(3) (Ln = La, Nd, Lu) has been evaluated. The isolated mono- and binuclear complexes, namely, [UO2(NO3)(2)L] (1), [{UO2(NO3) L}(2)(mu(2)-O-2)]center dot EtOH (2), [La(NO3)(3)L-2]center dot 2.33MeCN (3), [Nd(NO3)(3)L-2]center dot 3MeCN (4), [Nd(NO3)(2)L-2](+)center dot(NO3)(-)center dot EtOH (5) and [Lu(NO3)(3)L-2] (6) have been characterized by IR spectroscopy and elemental analysis. Single-crystal X-ray structures have been determined for complexes 1-5. Intramolecular intraligand pi-stacking interactions between two phenyl fragments of the coordinated ligand(s) were observed in all complexes 1-5. The pi-stacking interaction energy was estimated from Bader's AIM theory calculations performed at the DFT level. Solution properties have been examined using IR and multinuclear (H-1, C-13, and P-31) NMR spectroscopy in CD3CN and CDCl3. Coordination modes of L vary with the coordination polyhedron of the metal and solvent nature showing many coordination modes: P(O), P(O), P(O), P(O), C(O), P(O), C(O), and P(O). Preliminary extraction studies of U(VI) and Ln(III) (Ln = La, Nd, Ho, Yb) from 3.75 M HNO3 into CHCl3 show that scorpionate L extracts f-block elements (especially uranium) better than its unmodified prototype (OPPh2)(2)CH2.