Cyclopolysilanes structure

Methyl groups on cyclopolysilanes can also be substituted by halogens without destruction of the ring structure. With SbCls, for instance two or three methyl groups can be removed from (Me2Si)6 depending on the stoichiometric ratio of the reactants. In case of the dichlorodecamethylcyclohexasilanes, the 1,3- and 1,4-isomers are produced exclusively (Scheme 11). Formation of the 1,2 dichloride was never observed. 

Partially functionalized cyclopolysilanes recently attracted attention as model substances for siloxene and luminescent silicon. The yellow luminescent silicon is formed by the anodic oxidation of elemental silicon in HF-containing solutions and may be used for the development of silicon-based materials for light-emitting structures which could be integrated into optoelectronic devices77. Because the visible photoluminescence of... 

Although the structures of cyclopolysilanes can be similar to the carbon analogs, the methods of synthesis are not. The majority of the systems studied result from the selfcondensation of R2SiCl2 or RR SiCl2 which provide cycles of different sizes and with identical substituents at each silicon center. Of course, it is possible to cocondense two different dichlorosilanes, however then not only are rings of different sizes produced but isomers within each ring size are generated265 and separation can be a real problem. Clearly this area of catenated silicon derivatives would benefit from other reaction methods. 

A prerequisite for an understanding of the luminescence properties of siloxene is to understand its solid-state structure. In the following section, the present knowledge about the structure of siloxene is briefly reviewed, and this is followed by a short summary of current studies aimed at rebuilding siloxene-like structures from well-defined molecular precursors to obtain structurally well defined sub-elements of the siloxene lattice. Particular attention will be devoted to the question as to whether the fluorescence properties of siloxene can be matched by selectively prepared siloxene sub-units or substituted cyclopolysilanes. 

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