Complexation of Lanthanides with N,N,N′,N′-Tetramethylamide Derivatives of Bipyridinedicarboxylic Acid and Phenanthrolinedicarboxylic Acid: Thermodynamics and Coordination Modes

Abstract

The thermodynamics of Nd(III) and Eu(III) complexes with N,N,N′,N′-tetramethyl-2,2′-bipyridine-6,6′-dicarboxamide (TMBiPDA) and N,N,N′,N′-tetramethyl-1,10-phenanthroline-2,9-dicarboxamide (TMPhenDA) in CH 3 OH/10%(v)H 2 O solutions were studied. Stability constants and enthalpies of complexation were determined by absorption spectrophotometry, luminescence, and calorimetry. The stability constants of corresponding lanthanide complexes decrease in the order of TMPhenDA > TMBiPDA, while those of the corresponding ligand complexes with lanthanides decrease in the order of Nd(III) > Eu(III). The stepwise reactions for all 1:1 complexes as well as for the 1:2 Nd(III) complexes are driven by both enthalpy and entropy, while those for the 1:2 Eu(III) complexes are driven by entropy. The stronger affinity of TMPhenDA to Nd(III) and Eu(III) than that of TMBiPDA is predominantly arisen from its high preorganization. The spectra of the complexes in solutions are similar, implying that Nd(III) and Eu(III) coordinate with the two ligands in the same mode, which have been validated by 1 H and 13 C NMR titrations using La(III) as lanthanide tracer. The luminescence lifetimes of the Eu(III) complexes with TMBiPDA and TMPhenDA were evaluated by TRLFS. Structures of Nd(III)/TMPhenDA and Eu(III)/TMPhenDA complexes, identified by single-crystal X-ray diffractometry, show that ligand coordinates to metal in a tetradentate mode via two aromatic N-donors and two amide Odonors, and the central cation (Nd(III) or Eu(III)) is 10-coordinated by two whole TMPhenDA and two solvent (water or methanol) molecules. The M−O bond distances are almost identical, while the Nd−N bond distance is shorter than the Eu−O bond.

Influence of a N-Heterocyclic Core on the Binding Capability of N,O-Hybrid Diamide Ligands toward Trivalent Lanthanides and Actinides

“…Also, the average Nd/Er/La–O L bond length [2.46(13)/2.43(10)/2.36(14)/2.50(15) Å] is shorter than that of Nd/Er/La–N L [2.63(14)/2.63(12)/2.54(16)/2.77(17) Å] because the basicity of the O donor is harder than that of the soft N donor. Similar results have also been found in the lanthanide complexes with other N,O-mixed ligands …”

“…In order to provide more microscopic information for elucidating the complexation mechanisms of these three ligands with trivalent lanthanides and actinides, single crystals of the Pyr-PyDA, Pyr-BPyDA, and Pyr-DAPhen complexes with trivalent lanthanides suitable for X-ray diffraction analysis were prepared using the solvent diffusion method. 62,63 The crystal structures of the typical lanthanide complexes with three ligands, Nd(Pyr-PyDA)(NO 3 ) 3 CH 3 OH (1), Nd(Pyr-BPyDA)(NO 3 ) 3 (2), Er(Pyr-DAPhen)(NO 3 ) 3 (3), and La(Pyr-DAPhen)-(NO 3 ) 3 CH 3 OH (4), are presented in Figures 4 and 5, and the selected average bond distances of these crystal structures were comparatively listed in Table 2. The detailed structural refinement parameters are given Table 3.…”

“…Similar results have also been found in the lanthanide complexes with other N,O-mixed ligands. 3 Solvent Extraction Properties. Solvent extraction experiments were performed to evaluate the ability of the three structurally similar bipyridine-or pyridine-based ligands in highly acidic solutions.…”

“…Nowadays, nuclear power, which has low or even no carbon dioxide emissions, has become an effective strategy to deal with the energy crisis and climate change. , However, one significant shortcoming of nuclear energy is the need to dispose of the spent nuclear fuel (SNF) , generated from nuclear plants. Although most of the U and Pu in SNF can be recycled through the PUREX process, , the most problematic nuclides, that is, long-lived and highly radioactive minor actinides , (MAs) like Am­(III) and Cm­(III), still contain PUREX raffinate (so-called highly active liquid waste) .…”

Preorganization of N,O-hybrid phosphine oxide chelators for effective extraction of trivalent Am/Eu ions – a computational study

“…2 Nevertheless, one of the major flaws of nuclear power plants is the requirement of discarding the spent nuclear fuel (SNF). 3,4 Although the vast majority of the U and Pu in SNF can be reused through the PUREX (plutonium uranium reduction extraction) process, 5,6 the most hazardous nuclides, that is, the seemingly perpetual and exceptionally radioactive minor actinides (MAs), 7,8 like Am(III) and Cm(III), contain PUREX raffinate. 4 At present, the most advanced and effective technique to tackle this issue is the ''partition and transmutation'' (P&T) methodology, 4 whose central aim is to transform those long-lived radioactive nuclides into short-lived stable nuclides via the neutron-incited nuclear transmutation reaction.…”