Conjugated Polymers Inspired for Crystalline Silicon
Presented by Qifeng Jiang
Abstract:
Crystalline silicon, the semiconductor underlying computers, solar cells, and many other technologies, inspires synthesis of its molecular and polymeric mimics. Polycyclic fragments of chair cyclosilanes can be found in the structure of crystalline silicon lattice, which brings a revealing insight on designing novel silicon materials with tunable optical properties. The Klausen lab has been extensively exploring the target- oriented synthesis of cyclosilanes inspired by crystalline silicon in the past few years. We prepared three distinct polycyclosilanes: linear polymers synthesized from the cyclosilane building blocks 1,4Si6 and 1,3Si6, as well as a cyclic polymer of 1,3Si6. These polymers addressed how the microstructure of silane backbones affects thermal stability, phase properties, and pyrolysis. Meanwhile, We also developed a highly selective synthesis of new σ,π-conjugated cyclosilanes and investigated their potentials as building blocks for constructing novel conjugated structures with tunable electronic properties. While linear silanes are extensively studied, the shortage of methods for the controlled synthesis of well-defined cyclic materials has precluded the study of cyclic conjugation. Herein we report that Ru-catalyzed addition of cyclosilanes to aryl acetylenes (hydrosilylation) proceeds with high chemoselectivity, regioselectivity, and diastereoselectivity, affording complex organosilanes that absorb visible light. We further show that the hydrosilylation products are useful building blocks towards novel conjugated polymers with well-defined stereoregularity.
