A new interpretation of abnormal shift of water molecules' bending vibration frequencies in kieserite family monohydrates

Abstract

The Mn(II), Fe(II), Co(II), Ni(II), Zn(II) sulphate monohydrates, which are isomorphous to MgSO 4·H 2O, belong to the socolled kieserite family. A similar type of structure form CuSO 4·H 2O. Infrared spectra of these salts revealed characteristic spectral effects: (a) shifting of the δ HOH band in the range 1480–1520 cm −1, (b) appearance of low intensity bands at about 1720–1865 cm −1, and (c) in the spectrum of CuSO 4·H 2O, splitting of both bands into two components. The observed spectral effects can be assigned to coupled bending vibration of water molecules which form chains of MO wMO′ wM type in the crystal lattice.