A spectroscopic study of vibrations in crystalline compounds [Me(NH₃)₆] X₂

Abstract

Infra-red and Raman spectra of [Me(NH3)6]Xz crystals were measured for Me = Co, Ni and X-C1, Br, I. BF4, c104, PF6. The bands obtained were interpreted as being connected with vibrations of the [Me(NH3)6] octahedron. A far infra-red band at ca. 80 cm-I was interpreted as an IR active lattice mode. A lattice dynamics model based on electrostatic interactions between point ions was developed. A low frequency Raman active lattice mode was theoretically foreseen by this model.

Spectroscopy study of [Me(NH3)6]X2 compounds. II—Low frequency infrared and Raman spectra at various temperatures

“…I-ions, than for ions with a smaller number of electrons such as C1-ions. A strong decrease of the Raman active lattice band intensity with the lowering temperature may be explained by the population formula," which for Stokes bands is as follows (1) temperature falls from 300 K to 100 K. This is in qualitative agreement with the observed intensity lowering of the vL( 7'2,) band (with temperature) although in fact the intensity lowering is rather greater. No doubt there exists an additional effect resulting from the temperature dependence of the polarizabiity, which is neglected in Eqn.…”

“…No doubt there exists an additional effect resulting from the temperature dependence of the polarizabiity, which is neglected in Eqn. (1). In all our Raman spectra the very broad deformation band 8(NNiN)T2, at c. 240 cm-' splits into two bands as the temperature decreases.…”

FIR Spectra of [Ni(H2O)6](ClO4)2 and [Ni(D2O)6](ClO4)2 at Various Temperatures

“…The frequency peak at ca. 120 cm −1 corresponds to a T 1u translational lattice mode characteristic for all hexahydrates and hexaminates [7]. This band shifts to a lower frequency with increasing temperature (Figs.…”

“…Our interpretation is based on comparison with scarce spectroscopic data on hexahydrates [6] and quite rich data on similar hexaminates [7].…”