Fluorinated Tolane Dyads with Alkylene Linkage: Synthesis and Evaluation of Photophysical Characteristics

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.

D–π–A-type fluorinated tolanes with a diphenylamino group: crystal polymorphism formation and photophysical behavior

“…1b). 9 For the development of external stimuli-responsive luminophores, the formation of crystal polymorphism, which shows the same chemical composition with a different crystal structure, has become recognized as one of the promising approaches because luminescence behavior is strongly affected by crystal packing structures. 10 Organic luminophores containing triphenylamine units, in particular, have received much attention as a promising molecular design for the formation of crystal polymorphism due to their unique molecular structures, like a propeller-like conformation.…”

Fluorinated tolane-based fluorophores bearing a branched flexible unit with aggregation-induced emission enhancement characteristics

“…Moreover, we have reported dual-state fluorophores with large Stokes shifts, which consist of one or two fluorinated tolanes connected by an electron-withdrawing hexafluorocyclopentene scaffold 20,21 and mechanochromic luminescent diads that consist of two fluorinated tolanes tethered by a flexible chain. 22 Owing to the unsatisfactory photoluminescence (PL) efficiency (F PL ) of the reported tolane-based fluorophores, further molecular modulation is required for the appearance of versatile PL behavior, such as enhancement of PL efficiency and control of PL color. Toward the development of fluorinated tolane-based fluorophores with high F PL in the crystalline state, as shown in Fig.…”

Systematic Studies on the Effect of Fluorine Atoms in Fluorinated Tolanes on Their Photophysical Properties

“…[ 20 , 21 ]. Our extensive efforts have led to the successful development of fluorinated tolane-based PL molecules [ 22 , 23 , 24 ]. From our previous results, fluorinated tolanes were found to possess both crystallization-induced emission enhancement (CIEE) as well as aggregation-induced emission enhancement (AIEE) characteristics ( Figure 1 d) [ 23 , 24 ].…”