Triskelion‐Shaped π‐Luminophores Bearing Coumarin: Syntheses, Structures, and Luminescence Properties

Ueda, Masafumi; Kokubun, Mirai; Mazaki, Yasuhiro

doi:10.1002/cptc.202000049

Cited by 5 publications

(4 citation statements)

References 75 publications

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“…Finally, the targeted molecular triskelions 1A – E were obtained via an intramolecular Ullmann coupling reaction. The C 3 symmetric derivatives were fully characterized using 1 H and 13 C NMR spectroscopy and high-resolution mass spectrometry (HRMS) [ 28 , 29 ].…”

Section: Resultsmentioning

confidence: 99%

“…The molecular structures of 1A – D were confirmed using X-ray crystallography [ 28 , 29 ]. As expected, the molecular framework of 1 presented a helical geometry arising from intramolecular steric repulsion.…”

Section: Resultsmentioning

confidence: 99%

“…Our group has previously succeeded in synthesizing C 3 symmetric triskelion-shaped coumarin dye ( 1A ) and its donor-substituted derivatives ( 1B – 1E , Figure 1 c). Their molecular structures and photophysical properties have been reported [ 28 , 29 ]. X-ray crystallography revealed that the molecular framework of these compounds presented a helical geometry arising from intramolecular steric repulsion.…”

Section: Introductionmentioning

confidence: 99%

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Janus-Type AIE Fluorophores: Synthesis and Properties of π-Extended Coumarin-Bearing Triskelions

et al. 2022

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Janus-type triskelion-shaped fluorophores comprising coumarins bearing various electron-donating substituents (1aad, 1add, 1ccd, and 1cdd) were successfully synthesized via an intramolecular Ullmann coupling. Density functional theory (DFT) calculations indicated that all the compounds presented two different molecular surfaces, similar to Janus-type molecules. The absorption and fluorescence spectra of asymmetrical derivatives 1aad, 1add, 1ccd, and 1cdd exhibited a bathochromic shift due to their narrow highest occupied molecular orbital (HOMO) –lowest unoccupied molecular orbital (LUMO) gap. Natural transition orbital (NTO) analysis indicated that the excited state orbital overlaps differ among the C3 symmetrical and asymmetrical dyes. These triskelion-shaped fluorophores were found to form molecular nanoaggregates in THF/H2O mixtures and demonstrated aggregation-induced emission (AIE) enhancement characteristics as a result of restricting their molecular inversion. These results indicate that Janus-type AIE fluorophores are potentially applicable as solid-state fluorescent chiral materials, which can be optimized by controlling their molecular rearrangement in the solid state.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Janus-Type AIE Fluorophores: Synthesis and Properties of π-Extended Coumarin-Bearing Triskelions

et al. 2022

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“…Our group previously successfully synthesized a coumarin‐fused triskelion ( 1 , Figure 1c). [11] Compound 1 is an π‐extended coumarin dye with an invertible bowl‐shaped structure. Restricting the molecular inversion of aggregates of compound 1 can result in aggregation‐induced emission enhancement (AIEE).…”

Section: Introductionmentioning

confidence: 99%

Benzocoumarin‐Fused Triskelions Exhibit AIEE Due to Inhibited Molecular Inversion

Ueda,

Kuramochi,

Shimizu

et al. 2024

Eur J Org Chem

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Developing aggregation‐induced emission luminogens (AIEgens) is a unique strategy for alleviating concentration quenching of π‐conjugated organic compounds. This AIE behaviour can be induced not only in organic dyes with rotors but also in invertible π‐conjugated systems. Herein, intramolecular Ullmann coupling was used to synthesize π‐twisted triskelion‐shaped AIEgens (2F, 2G, and 2H), in which benzo[f], [g], and [h] coumarins were fused into the benzene core to form a helical propeller shape. These structural isomers had unique molecular thicknesses and planarities depending on the fusion mode of the benzocoumarin. The racemic crystals, PPP and MMM, had different overlapping molecular configurations because of their twisted molecular frameworks. Compounds 2F, 2G and 2H demonstrated weak fluorescence emission in diluted solutions resulting from molecular motions caused by the isomerization process during molecular inversion. By comparison, aggregates exhibited enhanced emission intensity. These π‐twisted triskelions exhibited the characteristics of AIEgens.

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Polarized, V-Shaped, and Conjoined Biscoumarins: From Lack of Dipole Moment Alignment to High Brightness

et al. 2022

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Eleven conjoined coumarins possessing a chromeno[3,4- c ]chromene-6,7-dione skeleton have been synthesized via the reaction of electron-rich phenols with esters of coumarin-3-carboxylic acids, catalyzed by either Lewis acids or 4-dimethylaminopyridine. Furthermore, Michael-type addition to angular benzo[ f ]coumarins is possible, leading to conjugated helical systems. Arrangement of the electron-donating amino groups at diverse positions on this heterocyclic skeleton makes it possible to obtain π-expanded coumarins with emission either sensitive to, or entirely independent of, solvent polarity with large Stokes shifts. Computational studies have provided a rationale for moderate solvatochromic effects unveiling the lack of collinearity of the dipole moments in the ground and excited states. Depending on the functional groups present, the obtained dyes are highly polarized with dipole moments of ∼14 D in the ground state and ∼20–25 D in the excited state. Strong emission in nonpolar solvents, in spite of the inclusion of a NO 2 group, is rationalized by the fact that the intramolecular charge transfer introduced into these molecules is strong enough to suppress intersystem crossing yet weak enough to prevent the formation of dark twisted intramolecular charge transfer states. Photochemical transformation of the dye possessing a chromeno[3,4- c ]pyridine-4,5-dione scaffold led to the formation of a spirocyclic benzo[ g ]coumarin.

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Triskelion‐Shaped π‐Luminophores Bearing Coumarin: Syntheses, Structures, and Luminescence Properties

Cited by 5 publications

References 75 publications

Janus-Type AIE Fluorophores: Synthesis and Properties of π-Extended Coumarin-Bearing Triskelions

Janus-Type AIE Fluorophores: Synthesis and Properties of π-Extended Coumarin-Bearing Triskelions

Benzocoumarin‐Fused Triskelions Exhibit AIEE Due to Inhibited Molecular Inversion

Polarized, V-Shaped, and Conjoined Biscoumarins: From Lack of Dipole Moment Alignment to High Brightness

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