Development of Novel Solid-State Light-Emitting Materials Based on Pentafluorinated Tolane Fluorophores

Abstract

We herein describe the synthesis of novel pentafluorinated tolane fluorophores, which possess an extended π-conjugated structure with a large molecular dipole moment along the longitudinal axis. We also report a detailed evaluation of both the photophysical and thermal behaviors of these fluorophores. All molecules displayed photoluminescence (PL) characteristics in both the crystalline state and in dilute solutions. The large longitudinal dipole moment induced solvatochromic PL behavior, which switched sensitively with changes in the solvent polarity. In addition, incorporation of the fluorinated tolane-based solid-state light-emitting moiety into the polymer side chain was found to be responsible for the PL characteristics observed in the solid state. It was also noteworthy that the polymerization protocol led to a significant enhancement in the thermal stability, with the thermal decomposition temperature increased by 90 °C. Accordingly, novel solid-state light-emitting materials with high thermal stabilities were successfully developed as promising candidates for use in light-emitting and optoelectronic applications.

2-Chloroalkoxy-Substituted Pentafluorinated Bistolanes as Novel Light-Emitting Liquid Crystals

“…Since the chemical properties of the chiral and racemic mixtures were the same, typical synthetic procedures and the spectral data only for S-configured S-2a and S-2b are reported below as selected examples. The molecular structures of bistolane 2a and 2b were characterized via spectroscopic analyses, such as 1 H, 13 C, and 19 F NMR spectroscopy; infrared (IR) We subsequently directed our attention toward novel pentafluorinated bistolane-type LELCs with branch structures in their flexible units because the electric or steric effect can induce dynamic changes of molecular dipoles and molecular arrangements in condensed phases ( Figure 1B). Therefore, in this article, we describe the molecular design and synthesis of novel pentafluorinated bistolane-type LELCs carrying flexible units with the branch structure shown in Figure 1b and present detailed evaluations of their LC and PL properties.…”

“…Since the chemical properties of the chiral and racemic mixtures were the same, typical synthetic procedures and the spectral data only for S-configured S-2a and S-2b are reported below as selected examples. The molecular structures of bistolane 2a and 2b were characterized via spectroscopic analyses, such as 1 H, 13 C, and 19 F NMR spectroscopy; infrared (IR) spectroscopy; and HRMS. The NMR spectra indicated that the products were sufficiently pure for the evaluation of their LC and PL properties.…”

“…1 H and 13 C NMR spectra were recorded using a Bruker AVANCE III 400 NMR spectrometer (Rheinstetten, Germany) ( 1 H: 400 MHz and 13 C: 100 MHz) in chloroform-d (CDCl3) solution, and the chemical shifts are reported in parts per million (ppm) using the residual proton in the NMR solvent. 19 F NMR (376 MHz) spectra were acquired using a Bruker AVANCE III 400 NMR spectrometer (Rheinstetten, Germany) in CDCl3 solution with CFCl3 (δF = 0 ppm) as an internal standard.…”

“…Recently, our group developed families of pentafluorinated tolane [13] and bistolane derivatives with alkoxy-type flexible chains (Figure 1a) [14,15] as promising LE materials and revealed that their PL can change depending on the electron-density distribution [16] or the molecular arrangement in the aggregated structure [13][14][15]. It was of great interest that the bistolane-type LE molecules showed not only PL, but also liquid-crystalline (LC) properties, namely light-emitting liquid crystals 2 of 16 (LELCs) [17][18][19][20], and the PL behaviors were found to change through the crystal (Cr) LC thermal phase transition.…”

1,2‐Disubstituted 3,3,4,4,5,5‐Hexafluorocyclopentenes as Bent Light‐Emitting π‐Conjugated Luminophores

“…Very recently, extensive research on fluorine‐containing functional materials, such as light‐emitting and liquid‐crystalline materials, has been conducted in our group, leading to the successful development of pentafluorinated diphenylacetylenes ( G ) and 1,2‐bis(phenylethynyl)benzenes ( H ), which exhibit photoluminescence (PL) behavior in both crystalline and dilute solution states (Figure ). During the course of our research, hexafluorocyclopentene derivatives bearing two pentafluorinated diphenylacetylene arms ( I ) have been found to exhibit intense yellow PL with large Stokes shifts in dilute solution.…”