Effect of fluorine atoms in flexible chains on the phase transitions and photophysical behavior of D–π–A-type 4-alkoxy-4′-cyanodiphenylacetylene

Yamada, Shigeyuki; Yoshida, Kôji; Sakurai, Tsuneaki; Hara, Mitsuo; Konno, Tsutomu

doi:10.1039/d2me00057a

Cited by 8 publications

(5 citation statements)

References 27 publications

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“…Syntheses of CN-terminated 1 and CO 2 Et-terminated 2 were performed using the common synthetic intermediate 4 , which was prepared by a Pd(0)-catalyzed Sonogashira cross-coupling reaction according to our previous report [ 16 , 20 ]. The CN-terminated molecules 1a and 1b were synthesized in 26% and 66% yield, respectively, via an addition–elimination reaction between pentafluorobenzonitrile and 4-semifluoroalkoxy-substituted phenylethynyllithium, which was readily prepared from 4 .…”

Section: Resultsmentioning

confidence: 99%

“…Although semifluoroalkoxy-containing D-π-A-type nonfluorinated tolanes were reported to exhibit an SmA LC phase [ 20 ], the LC phase disappeared in the case of fluorinated tolane scaffolds. The phase transition enthalpies between the Cry and isotropic (Iso) phases of 1a and 1b were very large, which is attributed to the remarkable stabilization of the Cry phase by the introduction of fluorine atoms on the tolane backbone.…”

Section: Resultsmentioning

confidence: 99%

“…It has been shown that incorporating a semifluoroalkyl flexible chain unit into a mesogenic core is an effective molecular design approach to effectively express the Sm LC phase [ 18 , 19 ]. In fact, our recent study has reported that incorporating a semifluoroalkoxy fragment into D-π-A-type nonfluorinated tolane exhibits a smectic A (SmA) phase as well as weak photoluminescence ( Figure 2 a) [ 20 ]. Based on the knowledge of fluorinated PL molecules in our group, we conceived that a D-π-A-type fluorinated diphenylacetylene tolane containing a semifluoroalkoxy chain provides efficient PLLC molecules that exhibit efficient PL in the condensed phase ( Figure 2 b).…”

Section: Introductionmentioning

confidence: 99%

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Donor-π-Acceptor-Type Fluorinated Tolane Containing a Semifluoroalkoxy Chain as a Condensed-Phase Luminophore

et al. 2023

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Photoluminescent liquid-crystalline (PLLC) molecules, which can easily tune the PL behavior through the crystal (Cry)–LC phase transition, have attracted significant attention. Previously, we have demonstrated that the incorporation of a semifluoroalkoxy chain into π-conjugated mesogen is a promising approach for developing PLLC molecules with PL and SmA LC characteristics. We focused on the LC and PL characteristics of the molecules induced by the semifluoroalkoxy chain and fluorinated tolanes in the condensed phase. In this study, we developed cyano- or ethoxycarbonyl-terminated donor-π-acceptor-type fluorinated tolanes containing a semifluoroalkoxy flexible chain. The cyano-terminated fluorinated tolanes exhibited intense light-blue photoluminescence in the crystalline phase and did not exhibit any LC phase. In contrast, blue photoluminescence in the ethoxycarbonyl-terminated analogs was slightly weak; however, they exhibited Cry–SmA phase transition during the heating and cooling processes. The PL intensity of the ethoxycarbonyl-terminated fluorinated tolanes significantly decreased in the SmA phase; however, their PL colors changed during the Cry–SmA phase transition. This indicates that the developed tolanes are promising temperature-dependent PL materials, such as PL thermosensors or PL thermometers.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Donor-π-Acceptor-Type Fluorinated Tolane Containing a Semifluoroalkoxy Chain as a Condensed-Phase Luminophore

et al. 2023

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“…Therefore, to confirm the LC property of fluorinated tolanes, we investigated decyloxy‐substituted fluorinated tolanes: 15‐F with a CN group, 16‐F with an COOEt group, 4‐F with a methoxy group, and 12‐F with a decyloxy chain (Figure 13). [27] Additionally, replacement of the decyloxy chain with a partially fluorinated semifluoroalkoxy chain (e. g., nonafluorodecyloxy chain) can induce a smectic (Sm) LC phase with ordered structures [28] . Thus, we investigated 17‐F with a CN group and 18‐F with an COOEt group (Figure 13).…”

Section: Applications To Photoluminescent Liquid‐crystalline (Pllc) M...mentioning

confidence: 99%

Development of Donor‐π‐Acceptor‐Type Fluorinated Tolanes as Compact Condensed Phase Luminophores and Applications in Photoluminescent Liquid‐Crystalline Molecules

Yamada

Konno

2023

The Chemical Record

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Fluorinated tolanes, produced by introducing fluorine atoms into one of the aromatic rings of tolane, emitted almost no fluorescence in a solution state, but the fluorescence intensity increased dramatically in the crystalline state because of intermolecular H⋅⋅⋅F hydrogen bonds. The photoluminescent (PL) colors depend on the molecular orbitals, dipole moments, and molecular aggregated structures can be varied by controlling terminal substituents along the major molecular axis. The introduction of a long alkoxy or semifluoroalkoxy unit as a flexible chain into the terminal positions along the major molecular axis induced the formation of a liquid‐crystalline (LC) phase; fluorinated tolanes act both as luminophores and as mesogens, leading to the molecular design of new photoluminescent LC molecules (PLLCs). The results also indicated that a fluorinated tolane dimer, which consists of two fluorinated tolanes linked by a flexible alkylene spacer, also becomes a novel PLLC.

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“…Among our achievements, the D-π-A-type tolane bearing a decyloxy (C10H21O) chain formed a nematic (N) LC phase as a mesophase (Figure 1a) [19]. However, the formation of a mesophase of smectic A (SmA) was observed when the flexible chain was changed from a decyloxy chain to a semifluoroalkoxy chain, viz., C4F9-C6H12O or C6F13-C4H8O, in which a fluoroalkyl unit was introduced into the flexible-chain end (Figure 1b) [20]. In addition to their LC properties, these tolanes were found to possess fluorescent properties with a quantum yield (ΦPL) of up to 0.21, even in the crystalline state.…”

Section: Introductionmentioning

confidence: 99%

(1E)-1,2-Diaryldiazene Derivatives Containing a Donor–π-Acceptor-Type Tolane Skeleton as Smectic Liquid–Crystalline Dyes

Yamada,

Yoshida,

Eguchi

et al. 2024

Compounds

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Considerable attention has been paid to (1E)-1,2-diaryldiazenes (azo dyes) possessing liquid–crystalline (LC) and optical properties because they can switch color through thermal phase transitions and photoisomerizations. Although multifunctional molecules with both LC and fluorescent properties based on a donor–π-acceptor (D-π-A)-type tolane skeleton have been developed, functional molecules possessing LC and dye properties have not yet been developed. Therefore, this study proposes to develop LC dyes consisting of (1E)-1,2-diaryldiazenes with a D–π-A-type tolane skeleton as the aryl moiety. The (1E)-1,2-diaryldiazene derivatives exhibited a smectic phase, regardless of the flexible-chain structure, whereas the melting temperature was significantly increased by introducing fluoroalkyl moieties into the flexible chain. Evaluation of the optical properties revealed that compounds with decyloxy chains exhibited an orange color, whereas compounds with semifluoroalkoxy chains absorbed at a slightly blue-shifted wavelength, which resulted in a pale orange color. The thermal phase transition caused a slight color change accompanied by a change in the absorption properties, photoisomerization-induced shrinkage, and partial disappearance of the LC domain. These results indicate that (1E)-1,2-diaryldiazenes with a D–π-A-type tolane skeleton can function as thermo- or photoresponsive dyes and are applicable to smart windows and in photolithography.

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Effect of fluorine atoms in flexible chains on the phase transitions and photophysical behavior of D–π–A-type 4-alkoxy-4′-cyanodiphenylacetylene

Abstract: D-π-A-type 4-alkoxy-4ʹ-cyanodiphenylacetylenes bearing a decyloxy chain shows a nematic liquid crystalline (LC) phase, whereas the incorporation of a semifluoroalkyl fragment results in a switch to the smectic A phase. The...

Cited by 8 publications

References 27 publications

Donor-π-Acceptor-Type Fluorinated Tolane Containing a Semifluoroalkoxy Chain as a Condensed-Phase Luminophore

Donor-π-Acceptor-Type Fluorinated Tolane Containing a Semifluoroalkoxy Chain as a Condensed-Phase Luminophore

Development of Donor‐π‐Acceptor‐Type Fluorinated Tolanes as Compact Condensed Phase Luminophores and Applications in Photoluminescent Liquid‐Crystalline Molecules

(1E)-1,2-Diaryldiazene Derivatives Containing a Donor–π-Acceptor-Type Tolane Skeleton as Smectic Liquid–Crystalline Dyes

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