om060964k_si_001.cif (94.63 kB)

An Approach to Dendritic Oligosilanes:  Controlling the Conformation through Ring Formation

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posted on 02.04.2020 by C. Krempner, H. Reinke
The synthesis, solid-state structure, and UV spectroscopic properties of the first-generation single-core oligosilane dendrimer MeSi[SiMe2Si(SiMe3)2Me]2[SiMe2Si(SiMe3)3] (5) and the tethered analogue (CH2)4[Si(SiMe3)2SiMe2]2Si[SiMe2Si(SiMe3)3]Me (4) are reported. UV spectroscopic measurements in solution and in the solid state (diffuse reflectance) show the absorption maximum of tetramethylene-tethered 4 to be shifted to wavelengths longer than those of 5, the dendrimers MeSi[SiMe2Si(SiMe3)3]3 (6) and MeSi[SiMe2Si(SiMe3)2Me]3 (7), and even that of the linear heptasilane Si7Me16. This can be explained by the results of the X-ray analysis of 4 and 5, which reveal for 4 the presence of an A−D−A−D conformer, which is optimal for σ-conjugation, whereas in 5 only D−D−O−D conformers have been found.