Poly(cyclosilane) Connectivity Tunes Optical Absorbance

We report herein the influence of skeletal connectivity on the conformation-dependent optical properties ofcyclosilane homo- and copolymers. 1,3-Linked cyclosilanes werebathochromically shifted by 20 nm in solution relative to 1,4-linkedcyclosilanes, an effect reproduced by quantum chemical calcu-lations on oligomeric model systems. Polysilane optical propertiesare conformation-dependent, and 1,3-linked cyclosilanes werehypothesized to adopt a favorable conformation unavailable to 1,4-linked cyclosilanes constrained to an endocyclic gauche con-formation. Copolymerization of the isomeric cyclosilanes1,3Si6and1,4Si6afforded linear statistical copolymers, as characterizedby1H and29Si NMR spectroscopies. The distinct connectivity ofeach comonomer was found to give rise to tunable absorption spectra, where the position of the absorption band systematicallyincreased with the increased corporation of1,3Si6. Computational studies pointed to conformation-dependent changes in orbitalsymmetry in shifting the most intense transition from the low-energy highest occupied molecular orbital (HOMO)-> lowestunoccupied molecular orbital (LUMO) transition to a higher-energy HOMO -> LUMO +ntransition. The results of these studiesdemonstrate for thefirst time the role of silicon skeletal connectivity in controlling conformation and optoelectronic properties andprovide new insight into the structure-based design of solution-processable silicon-based polymeric materials

Automated summary

This study reports the influence of skeletal connectivity on the conformation-dependent optical properties of cyclosilane homo- and copolymers. The connectivity of cyclosilanes affects their conformation and absorption spectra, and computational studies reveal the role of skeletal connectivity in controlling the optoelectronic properties.