Vibrational spectroscopic studies of Guanidinium metal (MII) sulphate hexahydrates [MII=Co,Fe,Ni]

The Raman and FTIR spectra of [C(NH2)3]2M(SO4)2⋅6H2O (with M = Co, Fe, Ni) were recorded and analysed. The observed spectral bands are assigned in terms of vibrations of guanidinium ions, sulphate groups and water molecules. The analysis shows that the sulphate tetrahedra are distorted from their free state symmetry Td to C1. This is attributed to the presence of hydrogen bonds from water molecules. The order of distortion of the metal oxygen octahedra influenced the distortion of the sulphate tetrahedra. The appearance of ν1-ν3 modes of water molecules above 3300 cm−1 indicates the presence of weak hydrogen bonds.