Fluorine-containing bistolanes as light-emitting liquid crystalline molecules

Yamada, Shigeyuki; Miyano, Kazuya; Konno, Tsutomu; Agou, Tomohiro; Kubota, Toshio; Hosokai, Takuya

doi:10.1039/c7ob01369h

Cited by 40 publications

(38 citation statements)

References 48 publications

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“…In the case of 2-chlorohexyloxy-substituted bistolanes, e.g., S-2b and rac-2b, a similar phase transition was observed, but the transition temperature, i.e., Tm and the clearing temperature (Tc), in the cooling cycle slightly decreased (Tm = 88-89 °C and Tc = 143-144 °C) in comparison with those for the S-2a (Tm = 97 °C and Tc = 148 °C) and rac-2a (Tm = 102 °C and Tc = 148 °C) carrying the flexible 2-chloropentyloxy chain. In comparison with the previously reported phase transition behaviors of the linear analogues 1a and 1b [15], introduction of Cl into the flexible chain did not significantly change Tm, but did cause All bistolane derivatives with 2-chloroalkoxy flexible units showed LC phases during both heating and cooling. In the DSC measurements, S-2a displays a LC phase during the heating process, while two LCs are observed during cooling.…”

Section: Compoundcontrasting

confidence: 69%

“…According to the synthetic procedure shown in Scheme 1, the pentafluorinated bistolanes with the branched flexible chain 2a used in this study were prepared from 4-(2chloropentyloxy)phenylacetylene (3a), which was accessible from commercially available norvaline [15]. The S-and R-configured 2a, i.e., S-2a and R-2a, as well as a racemic mixture (rac-2a) were obtained in the same manner using the corresponding S-/R-or racemic norvaline.…”

Section: Methodsmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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In this study, we designed and synthesized novel pentafluorinated bistolane derivatives with 2-chloropentyl or 2-chlorohexyl flexible units as novel light-emitting liquid crystals (LELCs). By measuring the phase-transition behaviors, all derivatives were found to display liquid-crystalline (LC) phases during both heating and cooling processes. Among the novel bistolanes, the S- and R-configured derivatives exhibited a chiral nematic (N*) phase with a typical Grandjean optical texture. Interestingly, the chiral derivatives also exhibited a blue phase with a typical platelet texture in a narrow temperature range (2–4 °C). Photophysical measurements revealed that the 2-chloroalkoxy-substituted pentafluorinated bistolanes exhibited intense photoluminescence (PL) both in solution and in crystalline phases. The PL characteristics, especially the maximum PL wavelength, were found to switch sensitively during the heating and cooling cycles depending on the molecular aggregates through the crystal (Cr) ⇄ N* phase transition. The 2-chloroalkoxy flexible units induced dynamic changes in the LC and PL properties, providing valuable insight into the potential of various LELCs as PL sensing materials.

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Section: Compoundcontrasting

confidence: 69%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…The nematic phase of C 6 Ph‐HBT was emissive; its fluorescence characteristics were examined by variable‐temperature fluorescence spectroscopy measurements . A very weak emission band appeared at ≈525 nm in the I.L.…”

Section: Resultsmentioning

confidence: 99%

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Zhang

Sakurai

Aotani

et al. 2018

Advanced Optical Materials

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solid-state emitters, electroluminescent devices, organic lasers, and so on. [1][2][3][4][5] Particularly, emission through excitedstate intramolecular proton transfer (ESIPT) mechanism with an extremely large Stokes shift [6][7][8][9] (anti-Kasha rule) suppresses excitation energy dissipation via self-absorption, providing attractive material platforms for optical device fabrication. [10,11] ESIPT is a photochemical process that produces a tautomer with a different electronic structure from the original excited form (Figure 1a). The requisite of chemical structures for ESIPT is the presence of an intramolecular hydrogen bond (H-bond) between the proton donor (OH and NH 2 ) and the proton acceptor (N and CO) groups close to one another in a single molecule. Recent notable reports on the ESIPT fluorophores include the polymorph-dependent emissive crystals, [12,13] double proton transfer process with an extra-large Stokes shift, [14] amplified spontaneous emission, [15][16][17] lasing system, [18][19][20] environment-sensitive multicolored materials, [21][22][23][24] and the use as emitters with electrically generated intramolecular proton transfers. [25] Most of ESIPT molecules show significant fluorescence in the solid states, not suffering from "concentration quenching" and thus serving as aggregation-induced emission enhancement (AIEE) materials. [26][27][28] The ESIPT process requires structural relaxations upon proton transfer, and thus a certain conformational freedom is allowed for the molecular structures. [29] The conformational freedom results in allowing the possible nonradiative pathways especially in solution (Figure 1b), giving AIEE characters to the ESIPT molecules. [30,31] The AIEE character is advantageous because light outputs from the systems are extremely high embedded into actual devices to avoid the concentration quenching. [32] However, most of the previous ESIPT as well as AIEE systems have been mostly reported in the rigid solid phase such as single crystals, polycrystals, or powders [11,12] -not in liquid crystals (LCs). Although columnar LCs with ESIPT-active cores were reported, [33,34] simple rod-shaped LC molecules embedded with ESIPT-active group have been limited. [35,36] In contrast to columnar and cubic liquid crystal phases with highly ordered structures, nematic as well as several smectic subphases can easily align macroscopically by rubbed surfaces, mechanical stimuli, and electric and magnetic fields. [37][38][39] Fluorescence via excited-state intramolecular proton transfer (ESIPT) provides strong light emission with a large Stokes shift and environment-sensitive unique spectral patterns. Particular systems including 2-(2-hydroxyphenyl) benzothiazole (HBT) serve as efficient solid-state emitters with the ESIPT mechanism and aggregation-induced emission enhancement (AIEE) property, but have not been used for liquid crystalline (LC) materials. Here, rod-shaped fluorescent LCs with ESIPT characters are newly developed based on the HBT motif. The design of the targeted mole...

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“…Over the past few years, our group has intensively investigated fluorinated 1,4bis(2-phenylethyn-1-yl)benzenes (1), called bistolanes (Figure 2A), which show prominent fluorescence not only in dilute solution, but also in the crystalline state [27][28][29][30][31]. [25,26,32].…”

Section: Introductionmentioning

confidence: 99%

Development of fluorinated benzils and bisbenzils as room-temperature phosphorescent molecules

Yamada¹,

Higashida²,

Wang³

et al. 2020

Preprint

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Pure organic phosphorescent molecules are attractive alternatives to transition metal complexes-based phosphores for biomedical and technological applications owing to their abundance and nontoxicity. This article discloses the design, synthesis, and photophysical property of fluorinated benzil and bisbenzil derivatives as potential pure organic room-temperature phosphorescent molecules. These compounds were separately converted from the corresponding fluorinated bistolanes via PdCl2-catalyzed oxidation by dimethyl sulfoxide, while non-fluorinated bistolane provided the corresponding bisbenzil derivatives exclusively in a similar manner. Intensive investigation of the photophysical properties of the benzil and bisbenzil derivatives in toluene at 25 °C showed both fluorescence with a photoluminescence (PL) band at a maximum wavelength (λPL) of around 400 nm and phosphorescence with a PL band at a λPL of around 560 nm. Interestingly, intersystem crossing effectively caused fluorinated benzils to emit phosphorescence, which may be due to immediate spin-orbit coupling involving the 1(n, π)→3(π, π) transition, unlike the case of fluorinated or non-fluorinated bisbenzil analogues. These findings would become useful tool to develop novel pure organic room-temperature phosphorescent materials.

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Fluorine-containing bistolanes as light-emitting liquid crystalline molecules

Cited by 40 publications

References 48 publications

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

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

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Development of fluorinated benzils and bisbenzils as room-temperature phosphorescent molecules

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