Double-double effect of the inner transition elements

Fidelis, I.; Mioduski, T.

doi:10.1007/3-540-10788-6_2

Cited by 19 publications

(4 citation statements)

References 67 publications

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“…A second contribution to the stabilization of the ground state depends on the magnitude of the interelectronic repulsion (Racah E 3 parameter, approximated as D /10 in ref ) and the number of f electrons (−21 E 3 , for q = 3, 4, 10, and 11 and −9 E 3 for q = 2, 5, 9, and 12) . The mathematical expression for the change of the stabilization energy between two complexes of the same element Ln in equilibrium Δ E st then reads: , where a are prefactors for E 3 depending on the ground state L, while Δ E 1 and Δ E 3 are the changes of the Racah parameters E 1 and E 3 of Ln on complexation (see Table S14 for a list of these prefactors for the ground state of f n electron configuration) . Values of Δ E 1 and Δ E 3 cannot exceed typical nephelauxetic reductions 2% (see Table ).…”

Section: Results and Discussionmentioning

confidence: 99%

Periodic Trends in Lanthanide Compounds through the Eyes of Multireference ab Initio Theory

2016

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Regularities among electronic configurations for common oxidation states in lanthanide complexes and the low involvement of f orbitals in bonding result in the appearance of several periodic trends along the lanthanide series. These trends can be observed on relatively different properties, such as bonding distances or ionization potentials. Well-known concepts like the lanthanide contraction, the double-double (tetrad) effect, and the similar chemistry along the lanthanide series stem from these regularities. Periodic trends on structural and spectroscopic properties are examined through complete active space self-consistent field (CASSCF) followed by second-order N-electron valence perturbation theory (NEVPT2) including both scalar relativistic and spin-orbit coupling effects. Energies and wave functions from electronic structure calculations are further analyzed in terms of ab initio ligand field theory (AILFT), which allows one to rigorously extract angular overlap model ligand field, Racah, and spin-orbit coupling parameters directly from high-level ab initio calculations. We investigated the elpasolite Cs2NaLn(III)Cl6 (Ln(III) = Ce-Nd, Sm-Eu, Tb-Yb) crystals because these compounds have been synthesized for most Ln(III) ions. Cs2NaLn(III)Cl6 elpasolites have been also thoroughly characterized with respect to their spectroscopic properties, providing an exceptionally vast and systematic experimental database allowing one to analyze the periodic trends across the lanthanide series. Particular attention was devoted to the apparent discrepancy in metal-ligand covalency trends between theory and spectroscopy described in the literature. Consistent with earlier studies, natural population analysis indicates an increase in covalency along the series, while a decrease in both the nephelauxetic (Racah) and relativistic nephelauxetic (spin-orbit coupling) reduction with increasing atomic number is calculated. These apparently conflicting results are discussed on the basis of AILFT parameters. The AILFT derived parameters faithfully reproduce the underlying multireference electronic structure calculations. The remaining discrepancies with respect to experimentally derived data are mostly due to underestimation of the ligand field splittings, while the dynamic correlation and nephelauxetic effects appears to be adequately covered by CASSCF/NEVPT2.

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Section: Results and Discussionmentioning

confidence: 99%

Periodic Trends in Lanthanide Compounds through the Eyes of Multireference ab Initio Theory

2016

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“…The Racah parameters of aquo Ln3+ ions are expected to be greater than those of Ln3+ complexes in organic phases, because the aquo ions are less covalent than all the other Ln3+ complexes, with very few exceptions (Jorgensen, 1970). Fidelis and Mioduski (1981) have summarized the tetrad or double-double effects seen in the thermodynamic functions of complex formation, lattice con stants, and other properties of Ln and An com pounds. The evidence for the lanthanide tetrad effects in various geochemical samples has also been reported by Masuda and Ikeuchi (1979), Masuda et al (1987), and Kawabe et al (1991).…”

Section: Introductionmentioning

confidence: 99%

Lanthanide tetrad effect in the Ln3+ ionic radii and refined spin-pairing energy theory

1992

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The refined spin-pairing energy theory (RSPET) has been improved in order to understand quan titatively the tetrad or double-double effects recognized in the Ln3+ ionic radii. Since the ionic radii have been determined from the lattice constants and structural parameters of Ln01.5 and LnF3, the lattice energies of the compounds and the enthalpy difference of d Hf (LnF3)-A Hf (LnO1,5) have been exam ined by the improved RSPET. The RSPET parameters for the lowest levels of 4fq electronic configura tions strongly depend upon the effective nuclear charge (Z*). Such effects due to Z* have been taken into account. This made it possible to separate the variations in the lattice energies and the enthalpy difference across the Ln3+ series into the following two parts: (1) the large variation as a smooth func tion of q (the lanthanide contraction trend), and (2) the small zig-zag variation referred to the tetrad or double-double effect. The lattice energy of Ln01.5 and A Hf (LnF3)-A Hf (Ln01.5) exhibit upward con cave tetrad curves in their plots against q of Ln3+. The tetrad effect in the lattice energy of LnF3 is less conspicuous. This means that the Racah parameters for Ln3+ decrease very slightly in going from the gaseous free Ln3+ to LnF3, and then decrease greatly to Ln01.5, in accordance with the nephelauxetic series. The differences in Racah parameters between LnF3 and Ln01,5 have been estimated from A Hf(LnF3) -A Hf(Ln01.5) by means of an inversion technique based on the improved RSPET. The RSPET results for the thermochemical data are consistent with the careful spectroscopic determinations of Racah parameters for NdF3 and Nd01.5. Both the tetrad effect and the smooth lanthanide contraction seen in the Ln3+ ionic radii can be interpreted in terms of the quantum mechanical energetics of 4f elec trons.

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“…Such a phenomenon can be understood considering the so called "Lanthanide Tetrad Effect", which is originated from the disturbance of the coherent periodic lling of the f sub-shell of the electron conguration of trivalent lanthanides in four groups: La 3+ -Nd 3+ , Pm 3+ -Gd 3+ , Tb 3+ -Er 3+ and Tm 3+ -Lu 3+ . 23 Therefore, the effect of LnF 3 on the dehydrogenation performance of NaBH 4 is actually related to the f shell electron conguration of the Ln 3+ cation.…”

Section: Hydrogen Release and Uptake Behaviorsmentioning

confidence: 99%

“…5-up displays a W-type relationship between the DH d of 3NaBH 4 -LnF 3 and the c p of Ln 3+ , which is somewhat analogous to the relationship between Ln 3+ and their electronic congurations existing in a W-type tetrad effect. 23 It is worth noting that a V-type relationship between the DH f of 3NaBH 4 -LnF 3 and the c p of Ln 3+ is determined, which results from the changes of Ln oxidation states in the dehydrogenated products, and can be described using two lines with the intersection point at Nd 3+ (Fig. 5-down).…”

Section: Relationship Between the Enthalpy Change (Dh) And The Electr...mentioning

confidence: 99%

Effects of LnF₃ on reversible and cyclic hydrogen sorption behaviors in NaBH₄: electronic nature of Ln versus crystallographic factors

et al. 2015

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Double-double effect of the inner transition elements

Cited by 19 publications

References 67 publications

Periodic Trends in Lanthanide Compounds through the Eyes of Multireference ab Initio Theory

Periodic Trends in Lanthanide Compounds through the Eyes of Multireference ab Initio Theory

Lanthanide tetrad effect in the Ln3+ ionic radii and refined spin-pairing energy theory

Effects of LnF₃ on reversible and cyclic hydrogen sorption behaviors in NaBH₄: electronic nature of Ln versus crystallographic factors

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Double-double effect of the inner transition elements

Cited by 19 publications

References 67 publications

Periodic Trends in Lanthanide Compounds through the Eyes of Multireference ab Initio Theory

Periodic Trends in Lanthanide Compounds through the Eyes of Multireference ab Initio Theory

Lanthanide tetrad effect in the Ln3+ ionic radii and refined spin-pairing energy theory

Effects of LnF3 on reversible and cyclic hydrogen sorption behaviors in NaBH4: electronic nature of Ln versus crystallographic factors

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Effects of LnF₃ on reversible and cyclic hydrogen sorption behaviors in NaBH₄: electronic nature of Ln versus crystallographic factors