Spherosiloxanes and Spherometallosiloxanes

Abstract

Spherosiloxanes are regularly built spherical silsesquioxanes of the general formula (RSiO3/2)n (n = 8, 10, 12, …). A new class of materials is obtained, the spherometallosiloxanes, if some of the Si-atoms in the cage of the polyhedral siloxanes framework are replaced by metal atoms. The synthesis, the structure, and some properties of such molecules are discussed. We have discovered new synthetic routes to spherosiloxanes opening a field of many new interesting molecules. The NMR, IR, and Raman spectra are very simple due to the high symmetry of the molecules. Silanization is a highly successful form of surface modification. Silanes that are able to react with surface OH groups to form silyl-ether bonds can be bound covalently to a surface. We discuss surface-modification experiments based on this principle and report some recent results. Spherosiloxanes attracted our interest as model substances for investigating zeolites because of the resemblance of the framework structure of octasilsesquioxanes to the double four ring of zeolites. We focus on silver and copper zeolites, since they may be useful in an artificial photosynthesis system which is briefly explained.