Organosilicon Molecular Assembly, Synthesis, and Electron Transfer

Northwestern University, Evanston IL

Investigators

Abstract

This proposal describes several problems that involve organic molecules containing silicon, the atom just below carbon in the periodic table. The presence of silicon offers several advantages and, in fact, is the key component of all these problems. First, the high strength of the silicon-oxygen bond enables complex molecules to be self-assembled. Large rings with nanometer-sized cavities are designed to serve as hosts. Molecular recognition of the Si-O bond will demonstrate that organic-silicon compounds can have an interesting and useful aqueous chemistry. A new family of reagents will exert control on reactivity so that a single mirror image product is favored (enantioselectivity). Second, silicon is used to construct new molecular spherical and hemispherical cavities. Cyclodextrins and calixarenes will be attached to an organosilicate network to prepare microporous structures capable of binding with small molecules. An entirely new cavity-containing system that derives from a central silicon atom will be prepared. Third, electron transfer will be characterized along an all-silicon molecular backbone, that is, a silicon wire. This study will be the first attempt to characterize a molecular-sized wire based on an entirely non-carbon pathway. Fourth, new systems will be prepared in which silicon is positively charged and attached to only three other groups (silylium cations). And, fifth, silicon reagents will be used to prepare, at room temperature, new systems containing positively charged carbon (carbocations). With this renewal award, the Organic and Macromolecular Chemistry Program is supporting the research of Dr. Joseph B. Lambert of the Department of Chemistry at Northwestern University. Professor Lambert will focus his work on incorporating silicon into normal analogues of carbon compounds or into novel structures to create molecules with potentially important properties. The properties may be of theoretical interest or they may offer new practical applications. The scope of the project is increased by exploiting one of the reactions to devise a new method to add the silicon-hydrogen bond to carbon-carbon double bonds (hydrosilylation) in a process that is catalytic but avoids the use of precious metals necessary in the current process.