Thermal characterization of polysilanes has focused on the influence of organic side chains, whereas little is understood about the influence of silane backbone microstructure on thermal stability, phase properties, and pyrolysis.
Main group organometallic compounds can exhibit unusual optical properties arising from hybrid σ,π-conjugation. While linear silanes are extensively studied, the shortage of methods for the controlled synthesis of well-defined cyclic...
Silanes are important compounds in industrial and synthetic chemistry. Here, we develop a general approach for the synthesis of disilanes as well as linear and cyclic oligosilanes via the reductive activation of readily available chlorosilanes. The efficient and selective generation of silyl anion intermediates, which are arduous to achieve by other means, allows for the synthesis of various novel oligosilanes by heterocoupling. In particular, this work presents a modular synthesis for a variety of functionalized cyclosilanes, which may give rise to materials with distinct properties from linear silanes but remain challenging synthetic targets. In comparison to the traditional Wurtz coupling, our method features milder conditions and improved chemoselectivity, broadening the functional groups that are compatible in oligosilane preparation. Computational studies support a mechanism whereby differential activation of sterically and electronically distinct chlorosilanes are achieved in an electrochemically driven radical‐polar crossover mechanism.
We report herein the influence of
skeletal connectivity on the
conformation-dependent optical properties of cyclosilane homo- and
copolymers. 1,3-Linked cyclosilanes were bathochromically shifted
by 20 nm in solution relative to 1,4-linked cyclosilanes, an effect
reproduced by quantum chemical calculations on oligomeric model systems.
Polysilane optical properties are conformation-dependent, and 1,3-linked
cyclosilanes were hypothesized to adopt a favorable conformation unavailable
to 1,4-linked cyclosilanes constrained to an endocyclic gauche conformation.
Copolymerization of the isomeric cyclosilanes 1,3Si
6
and 1,4Si
6
afforded linear statistical copolymers, as characterized by 1H and 29Si NMR spectroscopies. The distinct connectivity
of each comonomer was found to give rise to tunable absorption spectra,
where the position of the absorption band systematically increased
with the increased corporation of 1,3Si
6
. Computational studies pointed to conformation-dependent changes
in orbital symmetry in shifting the most intense transition from the
low-energy highest occupied molecular orbital (HOMO) → lowest
unoccupied molecular orbital (LUMO) transition to a higher-energy
HOMO → LUMO + n transition. The results of
these studies demonstrate for the first time the role of silicon skeletal
connectivity in controlling conformation and optoelectronic properties
and provide new insight into the structure-based design of solution-processable
silicon-based polymeric materials.
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