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

Polarized electronic absorption spectra of Co2+ in trigonally compressed oc tahedra in brucite-type Co(OH)(2) have been measured at 290 and 90 K by mic roscope-spectrometric techniques and analysed in terms of the superposition model (SM) of crystal fields. The resulting SM and interelectronic repulsi on parameters are (B) over bar (4) = 5260, (B) over bar (2) = 4920, Racah B = 825, Racah C = 3550 cm(-1) at 290 K and (B) over bar (4) = 5320, (B) ove r bar (2) = 3900, Racah B = 830, Racah C = 3500 cm(-1) at 90 K (R-0 = 2.111 5 Angstrom; fixed exponential and spinorbit parameters t(4) = 5, t(2) = 3, zeta = 500 cm(-1)). Together with a recent SM analysis of Li2Co3(SeO3)(4), the (B) over bar (k) refined for Co(OH)(2) further confine the magnitude of the hitherto unknown `correct' SM parameters of Co2+ for future applicatio n to structurally and/or chemically less well defined systems.