Low frequency vibrational spectrum of Tutton's salts

Abstract

The infrared absorption spectrum of a representative member of the Tutton's double sulfates, K 2Co(SO 4) 2·6H 2O, has been recorded in the region 50–800 cm −1. The stretching vibrational frequencies of the OH⋯O bonds of these sulfates have been calculated, making use of the Lippincott and Schroeder potential function and the hydrogen bond lengths in these crystals reported in he crystal structure investigations. These data along with the Raman spectral data are compared and discussed in relation to the vibrational frequencies of the octahedral water complex, Co(H 2O) 6, present in the crystal and also with respect to the lattice oscillations. Group theoretical analyses of the external vibrations of the unit cell and the vibrational spectrum of Co(H 2O) 6 have been made. Tentative assignments of the vibrational frequencies are reported.