Superposition model analysis from polarized electronic absorption spectra of Co²⁺in trigonally distorted octahedra in brucite-type Co(OH)₂

Abstract

Polarized electronic absorption spectra of Co2+ in trigonally compressed octahedra in brucite-type Co(OH)2 have been measured at 290 and 90 K by microscope-spectrometric techniques and analysed in terms of the superposition model (SM) of crystal fields. The resulting SM and interelectronic repulsion parameters are B̄4 = 5260, B̄2 = 4920, Racah B = 825, Racah C = 3550 cm-1 at 290 K and B̄4 = 5320, B̄2 = 3900, Racah B = 830, Racah C = 3500 cm-1 at 90 K (R0 = 2.1115 Å; fixed exponential and spin-orbit parameters t4 = 5, t2 = 3, ζ = 500 cm-1). Together with a recent SM analysis of Li2Co3(SeO3)4, the B̄k refined for Co(OH)2 further confine the magnitude of the hitherto unknown `correct' SM parameters of Co2+ for future application to structurally and/or chemically less well defined systems.

Semi-ab initio calculations of superposition model and crystal field parameters for Co2+ ions using the exchange charge model

“…Their absorption spectra are typical for 6-fold coordinated Co 2+ ion and have been studied in details by Wildner and Andrut 23,25,26 using the Superposition Model and other empirical approaches.…”

Analysis of crystal-field effect on luminescence spectra of Mn4+ (3d3) ion-doped double perovskite La2ZnTiO6 phosphor by semiempirical computations: exchange charge model and superposition model

“…Importantly, the triclinic or monoclinic site symmetry induces the low-symmetry aspects that are inherent in CF and SPM analysis, which were investigated for several transition-metal ions, e.g., for Fe 3+ doped in triclinic (C 1 ) sites in TlInS 2 , 37 Cr 3+ doped in monoclinic (C 2 ) sites in YAl 3 (BO 3 ) 4 , 38 Cr 3+ doped in triclinic (C 1 ) sites in aluminosilicates (Al 2 O 3 :SiO 2 ), 39 Co 2+ in triclinic (C 1 , C i ) sites in Li 2 Co 3 (SeO 3 ) 4 , 40,41 Co 2+ in trigonal (D 3d ) sites in Co(OH) 2 , etc. 41,42 One of the aims of this paper is to unravel these aspects in La 2 ZnTiO 6 :Mn 4+ .…”

Operando Diffuse Reflectance UV-VIS Spectroelectrochemistry for Investigating Oxygen Evolution Electrocatalysts

“…At 396 nm and below that, bands arising from the splitting of the 2 H free ion term and the mixing with other states are expected. 25 Compared to the spectra of rock salt CoO nanoparticles (Fig. S2b), which also contain Co 2+ Oh (Oh, octahedrally coordinated by six oxygen atoms), the approximated Δ O value is larger (8428 cm −1 vs 7326 cm −1 ).…”

“…those are expected upon stretching or shrinking of an octahedron) leading to an increased absorption. 25,27 Furthermore, the increase could be also due to spin-orbit coupling originating in the 2 G free ion terms. 24 Zn 0.35 Co 0.65 O at 1.3 V vs RHE For the absorption spectra between 1.0 V and 1.3 V in Fig.…”