Sequential transformations of organic nitrogen functionalities in periodic mesoporous silica

Abstract

New methods for the sequential organic functionalisation of periodic mesoporous silica materials have been established. In a first step, organic-inorganic hybrid materials were synthesized by direct substitution at the silicon atoms of the channel structure with metalorganic reagents such as lithiated aromatics. The resulting nitrogen-containing nanostructured hybrid materials were subsequently converted in a second step by reactions such as azo-coupling and the Meerwein–Schuster reaction, respectively. These efficient and economic reactions lead to the formation of complex organic-inorganic hybrid materials with new functionalities, including quaternized ammonium salts, aromatic imines and peptides, as well as azo-compounds and stilbenes. The new nanostructured materials were characterized with a comprehensive set of structural and spectroscopic methods, including X-ray diffraction, thermoanalysis, nitrogen sorption, as well as Raman, IR, UV-vis and solid-state NMR spectroscopy.