Conjugated Polymers Inspired by Crystalline Silicon

Abstract

Modern technologies depend on the semiconductor silicon. Silicon nanostructures evince compelling properties including luminescence and biodegradability. Silicon-based soft matter is less explored, despite the attractive properties of conjugated polymers and small molecules inspired by crystalline silicon. This perspective describes the major synthetic approaches to polysilanes and summarizes innovations in the preparation of structurally complex functional polysilanes that combine unusual conjugation phenomena, solution processability, and morphological control. A connection is drawn between the limitations of current polymerization methodology and fine control of structure−property relationships.

Sila‐ and Germacarboxylic Acids: Precursors for the Corresponding Silyl and Germyl Radicals

“…To test the feasibility of this hypothesis,weexamined the reaction of silacarboxylic acid 1a as amodel Si substrate with benzyl acrylate 2a as ar epresentative alkene.A fter many attempts to optimize the conditions,w ef ound that the reaction proceeded with the highest efficiencyu nder visiblelight irradiation (l = 455 nm, blue LEDs) in MeCN solution with 4CzIPN as the catalyst, giving the desired silylation product 3aa in 82 %y ield, as determined by 1 HNMR spectroscopy (Entry 1, Table 1). In contrast to the optimal conditions,1 )nof ormation of 3aa was detected when Ir(pFppy) 3 ,[ Ir(ppy) 2 (bpy)]PF 6 ,I r[dF( t Bu)ppy] 3 ,o r[ Ru-(bpy) 3 ](PF 6 ) 2 (Entry 2) was used as the catalyst, and the yield decreased when [Ir(dFCF 3 ppy) 2 (dtbpy)]PF 6 was used (Entry 3);2 )the reaction did not proceed in solvents other than MeCN (Entry 4);3 )the reaction still took place smoothly in adiluted solution (Entry 5), but the yield decreased when the concentration of reaction solution was increased, owing to oligomerization of 2a (Entry 6);4 )increasing the amount of 1a did not greatly affect the reaction (Entry 7), but lowering the PC loading reduced the yield of 3aa (Entry 8);5 )no formation of 3aa was observed when the reaction was performed in the absence of light or PC (Entry 9), or in air (Entry 10).…”

“…Efficient and robust protocols for installing hetero‐element‐containing groups are important for the design and discovery of novel functional molecules. Organosilicon compounds are versatile tools in organic synthesis, and their unique physicochemical properties have led to widespread application in the fields of functional materials, life sciences, and drug discovery . In particular, silyl radicals are key intermediates for the synthesis and transformation of various organosilicon compounds and polymers .…”

Investigating the Microstructure of Poly(cyclosilane) by 29Si Solid-State NMR Spectroscopy and DFT Calculations

“…The synthesis of silicon-based soft matter is a growing field, with representative achievements in colloidal nanocrystals 1-5 , integrated nanocrystal-polymer hybrids, [5][6][7] donoracceptor chromophores, [8][9][10][11][12][13] molecular electronics [14][15][16][17][18][19] and conjugated polymers, [20][21][22][23][24][25][26] with potential applications as photovoltaic and photonic devices. [5][6][27][28][29][30][31][32] Recently, the dehydrocoupling polymerization of bifunctional cyclic precursors to provide polycyclosilanes has emerged as a route to functionalized polysilanes decorated with a periodic array of Si-Me and Si-H bonds (Scheme 1).…”

“…[5][6][27][28][29][30][31][32] Recently, the dehydrocoupling polymerization of bifunctional cyclic precursors to provide polycyclosilanes has emerged as a route to functionalized polysilanes decorated with a periodic array of Si-Me and Si-H bonds (Scheme 1). [24][25][26]33 A comprehensive understanding of structure-function relationship facilitates development of next-generation materials. However, structural characterization of polysilanes can be challenging because poor solubility and a lack of longrange periodic order hinder solution NMR spectroscopy and X-ray diffraction studies, respectively.…”

Isolation of a Cyclopentasilane from Magnesium Reduction of a Linear Hexasilane

“…[15] Towards the goal of uncovering new nanostructured materials that combine these compelling properties with the processability and tunability of organic conjugated polymers, we reported the synthesis of organosilicon polymer mimics of the crystalline silicon lattice such as polycyclosilane poly(1,4Si 6 ) (Scheme 1a). [16] Key to this work is the synthesis of multifunctional cyclosilanes [17,18] amenable to dehydrocoupling [19][20][21][22][23] or reductive polymerization. [24] The rational design and synthesis of new building blocks could further expand the structural and functional diversity of polycyclosilanes and other nanostructured silanes.…”