Current FWF-Projects

 

Heterosilaadamantanes (PIN 6819023)

 

1) Wider research context

Given the trend to ever increasing miniaturization of electronic devices, it is evident that this leads to electronic circuitry on a molecular scale. As silicon is the quintessential element for solid state electronics, the development of polysilane based electronic devices seems a reasonable idea. Small silaadamantane cages are molecular cutouts of the crystal lattice of elemental silicon and should provide a good starting point for the development of molecular Si-based molecular electronic circuitry components.

2) Hypotheses/research questions /objectives

The project aims to provide a thorough understanding of how to form these clusters and their higher analogs, how to dope them with different elements at specific positions and how to do functionalization, which is required to assemble different components and to interface them to conventional circuitry.

3) Approach/methods

Fundamentally different methods will be utilized to get access to the desired cluster molecules. The sila- Wagner-Meerwein (SWM) reaction rearranges alkylated polysilanes to their thermodynamically most stable isomers by a sequence of silyl and alkyl shifts. It involves the transient formation of silylium ions. The research groups of Marschner and Müller have already experience in the study of this reaction type. A unique feature of the SWM reaction is that, when applied to germasilanes, it places the Ge atoms at fully silylated positions of the cage structure. Conversely, the chloride promoted Aufbau reaction (CPA) utilizes the formation of trichlorisilanide ions by reaction of chloride with hexachlordisilane. The trichlorosilanide undergoes a chloride templated buildup of larger polysilanes such as the spectacular example of silafullerane. In the presence of dimethyldichlorogermane this reaction leads to the formation of silaadamantane cages.

4) Level of originality / innovation

Both methods (SWM and CPA) facilitate the formation of structurally complex polysilanes cages. Both can also be used to create polysilanes cages with heteroatoms at specific cage positions. However, they do not follow the same selectivity pattern. While the SWM reaction shifts Ge atoms to bridgehead positions, the CPA reaction places them in bridging ones. A similar trend can be observed for ring sizes, where the SWM favors formation of five-membered and the CPA six-membered rings. The innovative approach of this proposal is that the two reactions can be used to exploit the selectivities of both reaction types.

5) Primary researchers involved

Christoph Marschner (Graz) has huge experience in the synthesis and characterization of linear, cyclic and cage polysilanes. Thomas Müller (Oldenburg) has extensive experience in the theoretical analysis and mechanistic investigation of silylium chemistry. Matthias Wagner (Frankfurt) has uncovered the vast synthetic potential of the chloride promoted Aufbau reaction, which leads to heavily chlorinated polysilanes.

 

more informations about this project