Abnormally aggregation-induced emissions observed from hydrogen- and silyl-substituted siloles

Zhengang Han,Kefeng Xie

doi:10.1515/mgmc-2020-0015

Abstract

Abstract Silacyclopentadienes (siloles) are currently of great interest because of their intriguing aggregation-induced emission (AIE) characteristics. In this work, abnormally AIE phenomena were observed from silyl- and hydrogen-substituted siloles respectively. We propose silyl-substituent and hydrogen atom effects to explain this via both experiments and theoretical calculations. It was discovered that trimethylsilyl substituents destroyed the p-interactions with the silole core and resulted in the non-fluorescence. Additionally, 1-chloro-1-H-2,3,4,5-tetraphenylsilole featuring strong fluorescences in both solid and solution states with high fluorescence quantum yields represents a new potential photoelectric material. This work not only reports the silole with strong fluorescences in both solid and solution states for the first time but also contributs to enrich the AIE research of siloles.

Highlights

Owing to their good biocompatibility, versatile modification strategies, tunable spectral characteristics, and facile processability, organic luminophores are widelyIn 2001, Tang and coworkers observed a fantastic light emission phenomenon from some siloles, such as hexphenylsilole (HPS), which presented strong luminescence in the aggregated or solid state but become weakly emissive or non-emissive in the solution state
It is convinced that these aggregationinduced emission (AIE)-active siloles possess propeller-like noncoplanar structures and these peripheral “propellers” of siloles can freely rotate in the solution state, which deactivate excited states and weakens the fluorescence, while this rotated behaviour could be prevented by aggregated molecules and reinforce the fluorescence (Liang et al, 2015; Tang et al, 2001; Zhao et al, 2015)
High σ*-π* conjugation interactions between exocyclic carbon atoms and endocyclic silicon atom of siloles result in their low-lying lowest occupied molecular orbitals (LUMOs) (Yamaguchi and Tamao, 1998; Yamaguchi et al, 1998), which is favorable for their fluorescences in the solid state

Summary

Introduction

In 2001, Tang and coworkers observed a fantastic light emission phenomenon from some siloles, such as hexphenylsilole (HPS), which presented strong luminescence in the aggregated or solid state but become weakly emissive or non-emissive in the solution state. This “abnormal” fluorescence behavior is called aggregation-induced emission (AIE) (Luo et al, 2001). It is convinced that these AIE-active siloles possess propeller-like noncoplanar structures and these peripheral “propellers” of siloles can freely rotate in the solution state, which deactivate excited states and weakens the fluorescence, while this rotated behaviour could be prevented by aggregated molecules and reinforce the fluorescence (Liang et al, 2015; Tang et al, 2001; Zhao et al, 2015).

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