The experimentally observed extraction complexes of trivalent lanthanide Eu(III) and actinide Am(III)/Cm(III) cations with purified Cyanex301 [bis(2,4,4-trimethylpentyl)dithiophosphinic acid, HBTMPDTP denoted as HL], i.e., ML(3) (M = Eu, Am, Cm) as well as the postulated complexes HAmL(4) and HEuL(4)(H(2)O) have been studied by using energy-consistent 4f- and 5f-in-core pseudopotentials for trivalent f elements, combined with density functional theory and second-order Møller-Plesset perturbation theory. Special attention was paid to explaining the high selectivity of Cyanex301 for Am(III)/Cm(III) over Eu(III). It is shown that the neutral complexes ML(3), where L acts as a bidentate ligand and the metal cation is coordinated by six S atoms, are most likely the most stable extraction complexes. The calculated metal-sulfur bond distances for ML(3) do reflect the cation employed; i.e., the larger the cation, the longer the metal-sulfur bond distances. The calculated M-S and M-P bond lengths agree very well with the available experimental data. The obtained changes of the Gibbs free energies in the extraction reactions M(3+) + 3HL → ML(3) + 3H(+) agree with the thermodynamical priority for Am(3+) and Cm(3+). Moreover, the ionic metal-ligand dissociation energies of the extraction complexes ML(3) show that, although EuL(3) is the most stable complex in the gas phase, it is the least stable in aqueous solution.

Lanthanide(iii) hydration was studied by utilizing density-functional theory and second-order Møller-Plesset perturbation theory combined with scalar-relativistic 4f-in-core pseudopotentials and valence-only basis sets for the Ln(iii) ions. For [Ln(iii)(H(2)O)(h)](3+) (h = 7, 8, 9) and [Ln(iii)(H(2)O)(h-1)·H(2)O](3+) (h = 8, 9) molecular structures, binding energies, entropies and energies of hydration as well as Gibbs free energies of hydration were calculated using (8s7p6d3f2g)/[6s5p5d3f2g] basis sets for Ln(iii) and aug-cc-pV(D,T)Z basis sets for O and H in combination with the COSMO solvation model. At the generalized gradient approximation level of density-functional theory a preferred hydration number of 8 is found for La(iii)-Tm(iii) and 7 for Yb(iii)-Lu(iii), whereas hybrid density-functional theory predicts a hydration number 8 for all Ln(iii). At the SCS-MP2 level of theory the preferred hydration number is found to be 9 for La(iii)-Sm(iii) and 8 for Eu(iii)-Lu(iii) in good agreement with experimental evidence.

No abstract

A new method to determine localized complex-valued one-electron functions in the occupied space is presented. The approach allows the calculation of localized orbitals regardless of their structure and of the entries in the spinor coefficient matrix, i.e., one-, two-, and four-component Kramers-restricted or unrestricted one-electron functions with real or complex expansion coefficients. The method is applicable to localization schemes that maximize (or minimize) a functional of the occupied spinors and that use a localization operator for which a matrix representation is available. The approach relies on the approximate joint diagonalization (AJD) of several Hermitian (symmetric) matrices which is utilized in electronic signal processing. The use of AJD in this approach has the advantage that it allows a reformulation of the localization criterion on an iterative 2 × 2 pair rotating basis in an analytical closed form which has not yet been described in the literature for multi-component (complex-valued) spinors. For the one-component case, the approach delivers the same Foster-Boys or Pipek-Mezey localized orbitals that one obtains from standard quantum chemical software, whereas in the multi-component case complex-valued spinors satisfying the selected localization criterion are obtained. These localized spinors allow the formulation of local correlation methods in a multi-component relativistic framework, which was not yet available. As an example, several heavy and super-heavy element systems are calculated using a Kramers-restricted self-consistent field and relativistic two-component pseudopotentials in order to investigate the effect of spin-orbit coupling on localization.

The hydroquinoid phenanthrene Cr(CO) 3 complex 1, directly accessible from the benzannulation of pentacarbonyl[(methoxy)-1-naphthylcarbene]chromium with 3-hexyne as the kinetically favored isomer, and its thermodynamically stable haptotropomer 2 undergo a photoinduced substitution of one CO ligand for phosphines and phosphites PR 3 (R ) Me, OMe, Ph, OPh) to give (η 6 -phenanthrene)Cr(CO) 2 PR 3 complexes 3-10. Upon warming chromium complexes 3-6, a haptotropic metal migration affords regioisomers 7-10 in up to 79% yield bearing the chromium fragment coordinated to the terminal unsubstituted phenanthrene ring. The rearrangements have been monitored by IR and NMR spectroscopy. Kinetic NMR experiments in noncoordinating solvents such as hexafluorobenzene reveal first-order kinetics in line with an intramolecular metal shift along the extended π-system. The metal migration can be tuned by the P-based coligand as demonstrated by rate constants differing by 2 orders of magnitude and by barriers of activation differing by 15 kJ mol -1 , respectively. A quantitative analysis (QALE) of these ligand effects suggests that the rearrangement is controlled by both electronic and steric properties of the P-coligand. The molecular structures of the complexes 3, 4, and 6-10 were established by single-crystal X-ray analysis. Quantum chemical DFT calculations provide a mechanistic rationale of the haptotropic migration in naphthalene and phenanthrene Cr(CO) 2 PR 3 complexes.