How are heteroelements (Ga and Ge) incorporated in silicate oligomers?

The properties of microporous solids can be strongly influenced during the first stages of solid-state formation from solution. Furthermore, their properties are directly related to the presence, number, and character of intra- or extraframework heteroelements. In this contribution we studied the influence of the substitution of silicon against heteroelements, such as gallium and germanium. The aqueous prenucleating solutions were obtained by hydrolysis of the silicon and heteroelement sources in the presence of tetraalkylammonium cations. The time-resolved stepwise formation of larger oligomers was studied by using electrospray ionization mass spectrometry (ESI-MS). Furthermore, the structures of the obtained signals were verified by using MS/MS experiments, which led to the conclusion that strong structure-directing effects emerge from the introduction of heteroelements into the solutions.