Vibrational spectra of complex ring silicate anions - Method of recognition

In this work is presented an attempt to apply vibrational spectroscopy to study the structure of ring silicates, in particular to recognize the number of members in tetrahedra. A number of synthetic ring silicates prepared by various methods was subjected to the studies. They contained cations of various metals (Na, Ca, Sr, Pb), and the polyanions occurring in their structures differed in both the number of ring members (n = 3, 4 and 6) and the extent of deformation. The bands characteristic of the ring systems are located mainly in the middle IR spectra in the range 780-500 cm(-1). The bands due to Si-O vibrations were assigned as originating from both subunits containing bridging oxygen atoms (Si-O-Si) and those containing terminal oxygen atoms (Si-O-, broken bridges). The influence of crystalline field on the shape of the spectra has been analyzed. (C) 1997 Elsevier Science B.V.