title: Effects of lanthanoid cations on the first electronic transition of liquid water studied using attenuated total reflection far-ultraviolet spectroscopy: ligand field splitting of lanthanoid hydrates in aqueous solutions.
abstract: The effects of the lanthanoid cations (Ln(3+)) on the first electronic transition (Ã ← X̃) of liquid water were studied from the attenuated total reflection far-ultraviolet (ATR-FUV) spectra of trivalent Ln(3+) electrolyte solutions (1 M), except Pm(3+). The Ã ← X̃ transition energies of the Ln(3+) electrolyte solutions show a distinct tetrad in their dependence on the number of 4f electrons of the Ln(3+) cations. For the half occupation period of the 4f electrons, the Ã ← X̃ transition energies decrease from La(3+) (4f(0), 8.0375 eV) to Nd(3+) (4f(3), 8.0277 eV) and increase from Sm(3+) (4f(5), 8.0279 eV) to Gd(3+) (4f(7), 8.0374 eV). For the complete occupation period, there are two local minima at Dy(3+) (4f(9), 8.0349 eV) and Yb(3+) (4f(13), 8.0355 eV). The Ã ← X̃ transition energies of the tetrad nodes (La(3+), Gd(3+), Ho(3+) (4f(10)), and Lu(3+) (4f(14))) increase slightly, as the nuclear charge increases in accordance with the hydration energies of the Ln(3+) cations. The energy difference (ΔE) between the Ã ← X̃ transition energies and the line between La(3+) and Lu(3+) is largest at Nd(3+) (80.5 cm(-1)) for the half occupation period and at Dy(3+) (26.1 cm(-1)) and Yb(3+) (24.5 cm(-1)) for the complete occupation period. The order of magnitude of ΔE is comparable to the ligand field splitting (LFS) of the ground state multiplets of Ln(3+) complexes. The observed tetrad trend of the Ã ← X̃ transition energies of the Ln(3+) electrolyte solutions across the 4f period reflects the hydration energies of the Ln(3+) cations and the LFS induced by water ligands.
authors.affiliation: National Food Research Institute, National Agriculture and Food Research Organization (NARO), Tsukuba, Ibaraki 305-8642, Japan.
authors.forename: Takeyoshi
authors.initials: T
authors.lastname: Goto
authors.forename: Akifumi
authors.initials: A
authors.lastname: Ikehata
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Morisawa
authors.forename: Noboru
authors.initials: N
authors.lastname: Higashi
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Ozaki
mesh_terms: D004583:Electrons; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008024:Ligands; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D028581:Lanthanoid Series Elements; D008024:Ligands; D012996:Solutions; D014867:Water