Abstract
Light-emitting materials have received considerable attention because of their broad applications as substrates in bio-imaging and sensing components, light-emitting displays, and lighting devices. Herein, we developed fluorinated tolane and bistolane derivatives containing fluorinated aromatic rings and demonstrated their intense photoluminescence (PL) characteristics in crystalline powder states. We focused on molecules showing varied PL behavior with a change in the molecular aggregated structures. We synthesized novel fluorinated tolane dyads consisting of fluorinated tolane-based π-conjugated scaffolds and flexible alkylene linkages to control both the electron-density distribution and molecular aggregated states. Fluorinated tolane dyads connected with an alkylene linkage showed blue PL in a dilute solution, but the PL efficiency achieved was low. In contrast, the crystalline powder of tolane dyad substrates exhibited dual emission—relatively intense blue to deep blue PL—originating from monomer and aggregate emission. The PL behavior changed significantly with the alkylene linkage and the application of a mechanical stimulus to the crystalline powder sample. The fluorinated tolane dyads developed in this study could serve as stimulus-responsive photoluminescent materials suitable for optical applications.
Highlights
In the past few decades, significant advancements have been realized for light-emitting materials, and many such materials have been utilized in practical contexts [1,2,3]
We designed and synthesized novel fluorinated tolane dyads, which consist of fluorinated π-conjugated scaffolds with an intense crystalline state light-emitting property and flexible alkylene linkage that can dynamically change molecular geometries as well as aggregated structures in the crystalline powder state
In contrast to the PL behavior in dilute solutions, irradiation of UV light into the fluorinated tolane dyads in the crystalline powder states brought about significant change in the PL spectral shape for a variety of alkylene linkages, resulting in blue to deep blue PL emissions with a significant enhancement of ΦPL
Summary
In the past few decades, significant advancements have been realized for light-emitting materials, and many such materials have been utilized in practical contexts [1,2,3]. They are generally classified as solution or solid-state light-emitting materials. The former exhibits luminescence in the solution state and usually consists of an extended π-conjugated structure. Solid-state light-emitting materials show luminescence in solid states and are mainly applicable to light-emitting displays or lighting devices [7,8,9,10]. It has been challenging to develop solid-state light-emitting molecules due to the luminescence quenching effect induced by the formation of molecular aggregates [11]
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