Interaction of M³⁺ Lanthanide Cations with Amide, Pyridine, and Phosphoryl OPPh₃ Ligands:  A Quantum Mechanics Study

Abstract

We report an ab initio quantum mechanical study on the interaction of M(n)()(+) cations (M(n)()(+) = La(3+), Eu(3+), Yb(3+), Sr(2+), and Na(+)) with model ligands L for lanthanide or actinide cations: several substituted amides, pyridines, and the phosphoryl-containing OPPh(3) ligand. The interaction energies DeltaE follow trends expected from the cation hardness and ligand basicity or softness in the amide series (primary < secondary-cis < secondary-trans < tertiary) as well as in the pyridine series (para-NO(2) < H < Me < NMe(2)). Among all ligands studied, OPPh(3) is clearly the best, while the (best) tertiary amide binds lanthanides slightly less than the (best) pyridine-NMe(2) ligand. In the lanthanide 1:1 complexes, the energy differences DeltaDeltaE as a function of M(3+) (about 40 kcal/mol for all ligands) are less than DeltaDeltaE in the pyridine series (up to about 90 kcal/mol) where marked polarization effects are found. The conclusions are validated by a number of methodological investigations. In addition to optimal binding features, we also investigate the directionality of ion coordination to the ligands and the effect of counterions and stoichiometry on the structural, electronic and energetic features of the complexes. The results are discussed in the context of modeling complexes of lanthanide and actinide cations and compared to those obtained with analogous Na(+) and Sr(2+) complexes.

Do Perchlorate and Triflate Anions Bind to the Uranyl Cation in an Acidic Aqueous Medium? A Combined EXAFS and Quantum Mechanical Investigation

“…For the equatorial ligands the calculation shows different bond distances for the oxygen atoms of water (2.56 ) and triflate (2.37 ). [48,49] In the bidentate complex [UO 2 (CF 3 SO 3 ) 2 -(H 2 O) 2 ], the UÀS distance is only 3.20 , which confirms the assertion that the complexes found in solution are monodentate. About the same theoretical uranyl ± water distances (2.55 ) were found in gas- phase calculations by Spencer et al [14] Their results and similar ones for lanthanide complexes [47] furthermore show that the consideration of ªsolventº field effects can lead to a shortening of the metal ± ligand bonds by about 0.05 .…”

Cerium Oxyhydroxide Clusters: Formation, Structure, and Reactivity

“…Finally, a low abundance, but above background ion was measured at m/z 2944.4, which would correspond to [16,23, [13,12,29] -, using the notation of this paper. Exactly seven dehydration reactions of [13,12,29] -would produce the observed [13,19,15] -; however, if this were occurring then the absence of any of the higher hydrates is puzzling. An alternative concept might be direct LA formation of a [13,19,15] -Ce Keggin that can accommodate additional water molecules, but is not further hydrated because of slow addition kinetics and weak binding, perhaps suggesting datively bound water, in which case the hydrated version should be rather written as [13,15,19,(H 2 O) 7 ] -.…”

Understanding the Stability Trend Along Light Lanthanide Complexes with an Ehtylenediamine‐Type Ligand: A Quantum Chemical Study

“…Combined with the effective core potential, Density Functional Theory has been proved to be a powerful tool for determining different Ln‐complexes’ structures, bonding nature, stability and other properties . Using DFT, Wipff and co‐workers systematically studied the structures, Ln−L interaction, and energy features of Ln complexes formed with phosphoryl ligands . In 2014, M. Esrafili and colleagues evaluated the energy properties of a series of Ln‐β‐diketone, Ln‐β‐dithioketone, and Ln‐β‐diphosphine oxide complexes, respectively.…”