Synthesis and characterization of new polyoctahedral silsesquioxanes containing zinc coordination compounds on the surface

Abstract

The present work reports the synthesis and characterization of six new inorganic-organic hybrid materials containing Si8O12 (T8) or Si7O11H (T7) core built on polyoctahedral silsesquioxanes (POSS) backbone. To these units, tri-, penta- and hexadentate ligands containing N3, N4O and N5O coordinating sites were attached by reacting 3-(glycidyloxypropyl)trimethoxysilane (GPTMS) with primary/secondary amines followed self-condensation reaction, in basic medium. To prove that the ligands attached to the silicate backbone can bind metal ions, the materials were complexed with Zn(II) ions. The functionalized POSSs containing the ligands with N4O and N5O coordinating sites reacted with Zn(II) at 1:1 stoichiometric ratio. On the other hand, the reaction between the POSS containing the N3 ligand resulted in a stoichiometric ratio metal:ligand of 1:2. Infrared spectroscopy revealed the formation of siloxane cores. This feature was further confirmed by 29Si NMR, which is dominated by a signal around −67 ppm, typical of T3 sites.