Incorporating Methyl and Phenyl Substituted Stannylene Units into Oligosilanes. The Influence on Optical Absorption Properties

Abstract

Molecules containing catenated heavy group 14 atoms are known to exhibit the interesting property of σ-bond electron delocalization. While this is well studied for oligo- and polysilanes the current paper addresses the UV-absorption properties of small tin containing oligosilanes in order to evaluate the effects of Sn–Si and Sn–Sn bonds as well as the results of substituent exchange from methyl to phenyl groups. The new stannasilanes were compared to previously investigated oligosilanes of equal chain lengths and substituent pattern. Replacing the central SiMe2 group in a pentasilane by a SnMe2 unit caused a bathochromic shift of the low-energy band (λmax = 260 nm) of 14 nm in the UV spectrum. If, instead of a SnMe2, a SnPh2 unit is incorporated, the bathochromic shift of 33 nm is substantially larger. Keeping the SnMe2 unit and replacing the two central silicon with tin atoms causes shift of the respective band (λ = 286 nm) some 26 nm to the red. A similar approach for hexasilanes where the model oligosilane [(Me3Si)3Si]2(SiMe2)2 (λmax = 253 nm) was modified in a way that the central tetramethyldisilanylene unit was exchanged for a tetraphenyldistannanylene caused a 50 nm bathochromic shift to a low-energy band with λmax = 303 nm.

Group IV heteroadamantanes: synthesis of Si6Sn4and site-selective derivatization of Si6Ge4

“…12–15 We argue, however, that ‘truly mixed’ oligomers 16 with both E and E′ in their backbones also deserve thorough investigation, because here a particularly pronounced effect of the different properties of E and E′ on the electronic structure of the oligomeric scaffold can be anticipated. 17…”

“…[12][13][14][15] We argue, however, that 'truly mixed' oligomers 16 with both E and E 0 in their backbones also deserve thorough investigation, because here a particularly pronounced effect of the different properties of E and E 0 on the electronic structure of the oligomeric scaffold can be anticipated. 17 Recently, our group has shown that the Si 2 Cl 6 /[nBu 4 N]Cl silylation system, 18 which generates [SiCl 3 ] À as the reactive intermediate, 19,20 can be used in combination with R 2 GeCl 2 for the efficient synthesis of mixed Si,Ge-oligomers. Specifically, we prepared open-chain species (Cl 3 Si) 4 Ge 21,22 or Cl 3 Si-(R 2 Ge) n -SiCl 3 (n = 1, 2; R = Ph, nBu) and applied them as precursors in the chemical vapor deposition (CVD) of Si x Ge 1Àx alloys after hydrogenation.…”