We report a strategic synthesis of poly(cyclosilane), a well-defined polymer inspired by crystalline silicon. The synthetic strategy relies on the design of a functionalized cyclohexasilane monomer for transition-metal-promoted dehydrocoupling polymerization. Our approach takes advantage of the dual function of the phenylsilyl group, which serves a crucial role both in the synthesis of a novel α,ω-oligosilanyl dianion and as a latent electrophile. We show that the cyclohexasilane monomer prefers a chair conformation. The monomer design ensures enhanced reactivity in transition-metal-promoted dehydrocoupling polymerization relative to secondary silanes, such as methylphenylsilane. Comprehensive NMR spectroscopy yields a detailed picture of the polymer end-group structure and microstructure. Poly(cyclosilane) has red-shifted optical absorbance relative to the monomer. We synthesize a σ-π hybrid donor-acceptor polymer by catalytic hydrosilylation.

Silicon nanomaterials combine earth abundance and biodegradability with exceptional electronic properties. Strategic synthesis promises access to novel architectures with well-defined surface structure, size, and shape. Herein, we describe a five-step synthesis of functional macrocyclic polysilanes. Comparison of the materials isolated from isomeric building blocks provides evidence that building block directionality controls the shape of the resulting nanomaterial. Infrared (IR) and H andSi NMR spectroscopies, coupled to computational data, provide evidence of a well-defined Si-H and Si-Me terminated structure. The intrinsic porosity and the polarization arising from the hydridic character of the Si-H bond suggest applications in lithium-ion batteries, which are supported by quantum chemical calculations.

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.

We report the synthesis of both diastereomers of an all-silicon analog of decalin. Carbocyclic decalin is a ubiquitous bicyclic structural motif. The siladecalin synthesis provides materials functionalized with either Si−Ph or Si−H groups, versatile entry points for further chemical diversification. The synthesis of silicon-stereogenic silanes is significantly less precedented than the synthesis of asymmetric carbon centers, and strategies for control of relative stereochemistry in oligosilanes are hardly described. This study offers insights of potential generality, such as the epimerization of the cisisomer to the thermodynamically downhill trans-isomer via a hypothesized pentavalent intermediate. Decalin is a classic example in the conformational analysis of organic ring systems, and the carbocyclic diastereomers have highly divergent conformational profiles. Like the carbocycle, we observe different conformational properties in cis-and trans-siladecalins with consequences for NMR spectroscopy, optical properties, and vibrational spectroscopy. This study showcases the utility of targeted synthesis for preparing complex and functionalized polycyclic silanes.

Using high-resolution magic-angle spinning (MAS) solid-state NMR spectroscopy and density-functional theory (DFT) calculations, we determine the microstructure of the silicon-based functional polymer poly(1,4Si6) arising from the dehydrocoupling polymerization of cyclosilane 1,4Si6. 1H-29Si refocused-INEPT experiments allow the unambiguous determination of the number of attached protons to a silicon atom for each 29Si signal in 1,4Si6 and poly(1,4Si6). One-dimensional 1H→29Si cross-polarization MAS (CPMAS) spectra of poly(1,4Si6) show the development of SiH resonances upon polymerization and peak integration indicates an average degree of polymerization of 20. The 1H→29Si CPMAS spectrum of poly(1,4Si6) also shows two sets of isotropic signals, suggesting the presence of at least two distinct species. Two-dimensional 29Si dipolar double-quantum-single-quantum and single-quantum-singlequantum homonuclear correlation spectra reveal similar connectivity in the two species, pointing to stereochemical and/or conformational heterogeneity. DFT calculations on trimer models predict that chair or twist-boat conformations and with cis or trans diastereomers are all energetic minima. 29Si chemical shift calculations of the lowest energy structures show that conformers and stereoisomers are expected to give rise to distinct 29Si NMR peaks and likely explain the appearance of multiple sets of 29Si NMR signals. The strategy outlined here is expected to be widely useful for the microstructural elucidation of silicon-based functional polymers. Disciplines Disciplines Materials Chemistry Comments Comments