Unprecedented Route to Amide-Functionalized Double-Decker Silsesquioxanes Using Carboxylic Acid Derivatives and a Hydrochloride Salt of Aminopropyl-DDSQ

Abstract

An easy, efficient, and scalable synthetic procedure is described to obtain novel amide-functionalized double-decker silsesquioxanes (DDSQs). The use of mild conditions of deprotection of the BOC group, which does not result to the cleavage of the cage-like silsesquioxane structure, is reported. This method leads to the so far undescribed hydrochloride salt of aminoalkyl-DDSQ. Interestingly, the cis/trans-isomerization of DDSQ molecules was observed during the reaction. The resulting compounds are characterized using multinuclear NMR (1H, 13C, and 29Si), MALDI-TOF, FT-IR, and elemental analysis. Moreover, crystal structures are reported for three trans DDSQs. The chloride salt of aminoalkyl derivative, obtained in one of the steps of the synthetic pathway, shows an intriguing structure of the crystal lattice in which large channels are present, caused by ionic interactions in the lattice. The described approach opens the way to synthesizing new DDSQ derivatives and materials using BOC-blocked amines. We believe our findings would advance investigations about new materials based on little known organic–inorganic DDSQ-based hybrids.

Zn(II)–Siloxane Clusters as Versatile Building Blocks for Carboxylate-Based Metal–Organic Frameworks

“…Also, the combination of numerous carboxylate linkers and unprecedented SBUs of the general composition (RSiO 2 ) x M y would further enrich and deepen the understanding of MOF structures and properties. Finally, siloxanes are often considered as structural models for various building units of silicate minerals including zeolites, for example, polyhedral oligomeric silsesquioxanes mimicking the geometry of double n-rings found in various aluminosilicates. − Therefore, synthetic efforts toward geometrically diverse metal–siloxane SBUs may ultimately lead to hybrid materials in which building units of MOFs and zeolites are joined at the molecular level and not as a bulk composite. , …”