| Research Abstract |
1. In a series of the anti isomers of the ladder polysilanes, the absorption maxima of the longest wavelength shift to the longer wavelength region as the number of cyclotetrasilane rings progressively increases. The shift is explained in terms of the stabilization of the lowest unoccupied molecular orbitals (LUMO) by the extension of the Si-Si σ-conjugation. The ladder polysilanes can be readily reduced by Na and K to generate the radical anions. The remarkable feature of the resulting radical anions is their unusual stability. For example, in the absence of dioxygen, the half-life of the pentacyclododecasilane is too long to be measured. The X-ray crystallography disclosed that the anti ladder polysilanes can be seen as silicon double helices, in which two linear polysilane chains screw in one way and are bridged by Si-Si bonds. Chiral symmetry breaking could be realized for anti-tricyclooctasilane. The crystallization gave one large crystal of each enantiomer M or P.The oxidation of
… More
the bicyclohexasilane with a deficient amount of m-chloroperbenzoic acid (MCPBA) resulted in the formation of 7-oxa compound, which shows stronger UV absorption and fluorescence. The domino oxidation predominates in the tri-, tetra-, and penta-oxidations of the tricyclooctasilane, tetracyclodecasilane, and pentacyclododecasilane with MCPBA, respectively.
2. From the stereochemical results observed in the ring-opening of the cis, cis- and cis, transcyclotrisilane [Ph (Thex) Si]_3 (Thex=1, 1, 2-trimethylpropyl) with halogens, it is concluded that the cleavage of the Si-Si bonds occurs with retention -inversion of the configuration of the Si atoms.
3. Octathexyloctagermacubane was synthesized to allow a comparison of chemical and physical properties of the alkyl-substituted octasilacubane with those of the corresponding octagermacubane. The octagermacubane is very stable to UV-Visible light, suggesting the unusual electronic and photochemical properties of the polyhedral germanium framework. Less
|
