Figure 1 Sketch of possible Isomers for [SIW12O4]4-. Black circles correspond with charged oxygen atoms, single joined to W atoms. Triangles and hexagon sides represent W-O-W bonds. For simplicity, not all bonds and atoms were represented.
In “neutrum structure”, the four oxygen atoms bonded to Silicon atoms, are the charged atoms. In fact, the anion SiO4- is trapped into the neutral cage structure formed by oxygen and W atoms. This particular isomer is considered as two separated species. The stability of the different isomers proposed is evaluated calculating the total energy and dipole moment. Identifying the correct position of oxygen charged is a crucial step when we try to understand the mechanism for obtaining hybrid POMS materials.