Complexation of Lanthanides with Glutaroimide-dioxime: Binding Strength and Coordination Modes

Abstract

The complexation of lanthanides (Nd(3+) and Eu(3+)) with glutaroimide-dioxime (H2L), a cyclic imide dioxime ligand that has been found to form stable complexes with actinides (UO2(2+) and NpO2(+)) and transition metal ions (Fe(3+), Cu(2+), etc.), was studied by potentiometry, absorption spectrophotometry, luminescence spectroscopy, and microcalorimetry. Lanthanides form three successive complexes, M(HL)(2+), M(HL)L, and M(HL)2(+) (where M stands for Nd(3+)/Eu(3+) and HL(-) stands for the singly deprotonated ligand). The enthalpies of complexation, determined by microcalorimetry, show that the formation of these complexes is exothermic. The stability constants of Ln(3+)/H2L complexes are several orders of magnitude lower than that of the corresponding Fe(3+)/H2L complexes but are comparable with that of UO2(2+)/H2L complexes. A structure of Eu(3+)/H2L complex, identified by single-crystal X-ray diffractometry, shows that the ligand coordinates to Eu(3+) in a tridentate mode, via the two oxygen atoms of the oxime group and the nitrogen atom of the imide group. The relocation of protons of the oxime groups (-CH═N-OH) from the oxygen to the nitrogen atom, and the deprotonation of the imide group (-CH-NH-CH-) result in a conjugated system with delocalized electron density on the ligand (-O-N-C-N-C-N-O-) that forms strong complexes with the lanthanide ions.

Complexation of Manganese with Glutarimidedioxime: Implication for Extraction Uranium from Seawater

“…DFT Calculations were carried out to gain deeper insights into coordination geometry. The crystal structure of V(V), U(VI), Eu(III) and Fe(III) complex with glutarimidedioxime reveals that the ligand bind in a tridentate mode via the imide nitrogen and both oxime oxygens17202627. In these metal complexes, the imide nitrogens are deprotonated while the protons on both oxime oxygens are shifted onto the oxime N atoms.…”

Lanthanide Fluorobenzoates as Bio‐Probes: a Quest for the Optimal Ligand Fluorination Degree

“…It might thus be expected that thermodynamic stability of fluorobenzoate complexes should decrease with an increase of the number of fluorine atoms . This fact may also affect the solubility, which generally follows the opposite trend .…”

“…[36,62,63] Thisf act may also affect the solubility,w hich generallyf ollows the opposite trend. [36,62,63] Thisf act may also affect the solubility,w hich generallyf ollows the opposite trend.…”

A hydrolytically stable Ce(iv) complex of glutarimide-dioxime

“…[9][10][11][12][13] Glutarimide-dioxime (H 3 A, C 5 H 9 N 3 O 2 ), a compound reported to be useful for sequestering uranium from seawater, is considered here for stabilization of the cerium(IV) cation. H 3 A was originally known to extract uranyl (U VI [14][15][16][17][18] H 3 A was then developed to readily chelate simple metal ions, such as Ca(II), 19 Mg(II), 19 Cu(II), 20 Pb(II), 20 Ni (II), 20 Mn(II), 21 Fe(III), 20 Eu(III), 22 Nd(III), 22 and metals of high oxidation states, such as Th(IV), 23 Np(IV), 23 Pu(IV), 24 Np(V), 25 and V(V). [26][27][28] We reasoned it would similarly stabilize the Ce (IV) cation as in the high oxidation state metal complexes cases (Scheme 1).…”