The organosilicon materials with σ-π conjugated structures have raised broad interest for their unique optoelectronic properties and potential application in photoresists, emitting polymers and semiconductive materials. However, the σ fragments in these materials were largely limited to linear oligosilanes due to the small number of suitable building blocks and synthetic methods. To address this, the Klausen lab has extensively explored the design, synthesis, and polymerization of cyclosilanes. Herein we developed a highly selective synthesis of new σ-π conjugated cyclosilanes through hydrosilation and investigated their potentials as building blocks for constructing novel conjugated polymers with tunable electronic properties. Among these interesting cyclosilane structures, we found the bis-(bromothienylvinyl) cyclohexasilane particularly attractive. Treatment of it with 2.0 equiv. of isopropylnagnesium chloride resulted in a fast and quantitative conversion to a di-Grignard reagent, which showed potential as a new σ-π conjugated building block. Therefore, a conjugated alternating copolymer was synthesized through Kumada polycondensation of the di-Grignard reagent and 2,5-dibromothiophene. The average number molecular weight of the copolymer is ca. 7000 g/mol. The cyclosilane fragments were preserved in the polymerization shown by NMR spectroscopy. A significant bathochromic shift in UV-vis absorption spectra was observed after polycondensation: cyclosilane-320nm, copolymer-450nm. Moreover, the copolymer emitted bright green light with a maximum intensity at 520 nm. The results suggested the evidence of σ-π conjugation in the copolymer. Furthermore, different cyclosilane units and π conjugated comonomers were studied for the polycondensation, yielding conjugated polymers with tunable optoelectronic properties. This work describes the potential for cyclosilanes to increase the structural diversity of conjugated polymers.

Novel cyclosilane building blocks for constructing tunable σ-π conjugated structures

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.