Unsaturated Cyclopolysilanes

Open chained and cyclic molecules with carbon-element double bonds are of outstanding importance in organic chemistry e. g. in the fields of natural and pharmaceutical products, material science and plastics technology. Based on their considerably lower stabilities the corresponding silicon based species were long considered as "laboratory curiosities". Nevertheless, compounds with silicon-element double bonds were extensively investigated in the last 30 years so that nowadays a more or less detailed picture about their synthesis and reactivity exists. The majority of these studies, however, concerned open chained structures and not much is known about the corresponding rings. In particular cyclopolysilanes (cyclic molecules made up by silicon atoms) containing doubly bonded silicon atoms are of tremendous interest. Based on the unique bond structures likely featured by this class of compounds exceptional properties with respect to molecular structures, electronic spectra and reactivites such as long-wavelength light absorption, photochemical activity or photoluminescence can be expected. In the present project, thus, previously unknown cyclopolysilanes with silicon-element double bonds shall be comprehensively studied with the following primary targets: synthesis and complete characterization of the target compounds exploration of unusual reactivity patterns investigation of bonding properties within the target compounds applying modern structural, spectroscopic and electrochemical methods supported by computational studies From the results of this project we expect important contributions to the chemistry of the target compounds but also to a detailed theoretical description of Si=E multiple bonds which still continues to be controversial in the literature.

Open chained and cyclic molecules with carbon-element double bonds are of outstanding importance in organic chemistry e. g. in the fields of natural and pharmaceutical products, material science and plastics technology. Based on their considerably lower stabilities the corresponding silicon based species were long considered as "laboratory curiosities". Nevertheless, compounds with silicon-element double bonds were extensively investigated in the last 30 years so that nowadays a more or less detailed picture about their synthesis and reactivity exists. The majority of these studies, however, were focussed on open chained structures. Nnot much is known about the corresponding rings although for such cyclic molecules exceptional properties such as long-wavelength light absorption, photochemical activity or photoluminescence can be expected. In the course of this project synthetic approaches to previously unknown cyclopolysilanes (cyclic molecules made up by silicon atoms) and 1,4-disilacyclohexadienes with exocyclic Si=C bonds were developed and the properties and reactivities of the target molecules were investigated. Members of the latter class of compounds, in particular, represent excellent models to study cyclic cross-hyperconjugational type interactions between the endocyclic C=C- and the exocyclic Si=C double bonds via the bridging silicon atom. Furthermore, they exhibit great potential for future research because of their outstanding electronic nature and potential applications in electronic devices. Thus, from the obtained results of this project we expect considerable contributions to materials chemistry but also to a detailed theoretical description of Si=E multiple bonds which still continues to be controversial in the literature.