Enantiomerically Pure Helical Bilayer Nanographenes: A Straightforward Chemical Approach

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: unknown

Published: Dec. 6, 2024

The semiconductor properties of nanosized graphene fragments, known as molecular nanographenes, position them exceptional candidates for next-generation optoelectronics. In addition to their remarkable optical and electronic features, chiral nanographenes exhibit high dissymmetry factors in circular dichroism circularly polarized luminescence measurements. However, the synthesis enantiomerically pure remains a significant challenge. Typically, these materials are synthesized racemic form, followed by separation enantiomers using high-performance liquid chromatography (HPLC). While effective, this method often requires expensive instrumentation, extensive optimization conditions, typically yields analytical quantities desired samples. An alternative approach is enantioselective nanographenes; however, date, only two examples have been documented literature. work, we present straightforward chemical resolution helical bilayer nanographenes. This enables effective scalable preparation while avoiding need HPLC. incorporation BINOL core into polyarene precursor facilitates diastereomers through esterification with camphorsulfonyl chloride. Following standard chromatographic column, hydrolysis group nanographene precursors. subsequent graphitization, achieved Scholl reaction, occurs an enantiospecific manner concomitant formation furan ring heterohelicene moiety. absolute configurations final enantiomers, P-oxa[9]HBNG M-oxa[9]HBNG, determined X-ray diffraction. Additionally, electrochemical, photophysical, chiroptical thoroughly evaluated.

Language: Английский

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Unusually Short H⋅⋅⋅H Contacts in Intramolecularly Cyclized Helically Fused Anthracenes

Chemistry - A European Journal, Journal Year: 2024, Volume and Issue: 30(41)

Published: May 16, 2024

Abstract The intramolecular coupling of dichloro‐substituted helically fused anthracenes using the Yamamoto yielded cyclized products with sterically congested molecular structures. X‐ray analysis and DFT calculations showed that aromatic framework adopted a nonplanar structure twisted conformation about newly formed single bond, which acts as chiral axis. Interestingly, obtained through Hirshfeld atom refinement revealed short interatomic distances between inner hydrogen atoms (1.648–1.692 Å), much shorter than sum their van der Waals radii. Owing to these unusually contacts, 1 H NMR spectrum exhibited significant deshielding (12.5 ppm) large nuclear Overhauser effect (44 %). Additionally, IR displayed high‐frequency shift C−H stretching vibration. These observations, along noncovalent interaction plot indicative characteristic steric environment, strongly support presence hindrance. Moreover, dynamic measurement mesityl‐substituted derivative barrier helical inversion 84 kJ mol −1 . optical properties crystal packing are also reported.

Language: Английский

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The Effects of Pore Defects in π‐Extended Pentadecabenzo[9]helicene

Angewandte Chemie International Edition, Journal Year: 2024, Volume and Issue: 63(41)

Published: July 19, 2024

Abstract The introduction of precise pore defects into nanocarbon structures results in the emergence distinct physicochemical characteristics. However, there is a lack research on non‐planar chiral nanographene involving defects. Herein, we have developed two analogues to π‐extended pentadecabenzo[9]helicene ( EP9H ) containing embedded Each molecules, namely extended dodecabenzo[7]helicene ED7H ; 1 or nonabenzo[5]helicene EN5H 2 ), exhibits dual‐state emission. Significantly, value | g lum exceptionally high at 1.41×10 −2 solution and B CPL as 254 M −1 cm . In PMMA film, 8.56×10 −3 , powder it 5.00×10 This study demonstrates that molecules with exhibit emission properties while maintaining quite good luminescence properties. It was distinguished from aggregation‐caused quenching (ACQ) effect corresponding without defect. Incorporating also simplifies synthesis process enhances solubility resulting product. These findings suggest can be viable approach improve molecules.

Language: Английский

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Enantiomer-enriched π-Extended Helicenes with a Perylene Core from Binaphthol: Axial-to-Helical Chirality Transfer with Stepwise Scholl Reaction Mechanism

Chemical Science, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

Axially chiral substrates were transformed into enantiomer-enriched π-extended helicenes via a chiral-transfer-based Scholl reaction, and enantiomers efficiently separated without labor-intensive high-performance liquid chromatography (HPLC).

Language: Английский

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Double [8]Helicene Featuring a Dibenzo[g,p]chrysene Core: Synthesis and Chiroptical Response

Organic Letters, Journal Year: 2025, Volume and Issue: unknown

Published: May 2, 2025

Double [8]helicene 1, featuring a dibenzo[g,p]chrysene core, was synthesized via the Scholl reaction, and its structure unambiguously confirmed by single-crystal X-ray diffraction analysis of dicationic salt [1-Cl]2+·(SbCl6-)2. The compound exhibits red fluorescence with an emission maximum at 618 nm (λem) quantum yield 16.2%, highlighting potential in optoelectronic applications. Furthermore, circular dichroism (CD) circularly polarized luminescence (CPL) measurements reveal notable chiroptical activity, absorption dissymmetry factors |gabs| = 5.11 × 10-3 |glum| 7.1 10-4, respectively.

Language: Английский

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Topology-Directed Synthesis of Helical Phosphoniums with High Diradical Character and Polar-Dependent Electron Transfer

Chemistry of Materials, Journal Year: 2024, Volume and Issue: unknown

Published: Aug. 14, 2024

Molecular topology synthesis of polycyclic aromatic hydrocarbons (PAHs) with diradical character takes root in intramolecular coupling breakthrough. Herein, we report selective Mn(III)/Cu(II)-mediated C–P and C–H bond cleavage to obtain robust donor-fused phosphoniums helical or planar geometries distinct cationic charges. The former structures incorporate a common phospha[5]helication acceptor different arylamine donors, the latter structure contains phospha[6]dication same donors. These unprecedented ionic salts hold distinguishing donor–acceptor (D–A) constructions, showing unique topology-dependent optoelectronic properties. folded radical ammoniums possess an extreme electron-deficient state through-space isolation high (y0 = 0.989). Moreover, tunable charge transfer (CT) locally excited (LE) transition components facilitate diverse hybridized local (HLCT) solvents, endowing highest emission band gap variation 0.78 eV (∼217 nm). fluorescence radiation could also be adjusted from blue near-infrared regions via tailoring polar-dependent states, which output additional circularly polarized luminescence compatible chiral menthol matrix elevated quantum efficiency undisturbed deep-red glow. It is worth mentioning that atomically precise Mn(III) halide has been unprecedentedly captured determined for activation.

Language: Английский

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Conformational, Structural, and Chiroptical Properties of an Overcrowded Triply Fused Carbo[7]helicene

The Journal of Organic Chemistry, Journal Year: 2023, Volume and Issue: 89(1), P. 498 - 504

Published: Dec. 22, 2023

Recently, the synthesis of racemate an overcrowded triply fused carbo[7]helicene formula C66H36 with three carbo[7]helicenes within a central six-membered ring was described. This molecule found to embed extremely contorted and two negative curvatures. We report herein resolution corresponding enantiomers their conformational, structural, photophysical, chiroptical properties. The racemization determined proceed at rate krac = 8.06 × 10–4 s–1 175 °C in ortho-dichlorobenzene, barrier enantiomerization ΔGenant‡ 140.4 kJ·mol–1, value significantly lower than for pristine carbo[7]helicene. Interestingly, crystalline structures racemic enantiopure materials show some differences regarding molecular geometry, increased curvature latter cases. unusual curved delocalized π-conjugated system afforded notably green fluorescence room temperature far-red phosphorescence low temperature. Finally, electronic circular dichroism circularly polarized luminescence responses compounds have been measured showed very close absorption emission dissymmetry factors, gabs glum, respectively, ca. 2.6 10–3, indicating similar chiral rigid geometry both ground excited states.

Language: Английский

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Synthesis of Azahelicenes via Friedel‐Crafts‐Type Ring‐Closing Reaction of Axially Chiral Compounds

Asian Journal of Organic Chemistry, Journal Year: 2024, Volume and Issue: 13(7)

Published: May 9, 2024

Abstract Aza[6]helicene and aza[7]helicene were synthesized by Fridel‐Crafts‐type cyclization of axially chiral compounds. From the compounds prepared Fischer indole synthesis, aza[6]helicene synthesized. Aza[7]helicene was also from an pyrrole compound Piloty‐Robinson‐type synthesis through simultaneous on both sides ring. isomerized readily at room temperature, while isomerization temperature less likely to proceed. The cell growth inhibitory activity each enantiomer N ‐Me‐aza[7]helicene in HeLa cells examined. Differences strength between enantiomers observed.

Language: Английский

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The Effects of Pore Defects in π‐Extended Pentadecabenzo[9]helicene

Angewandte Chemie, Journal Year: 2024, Volume and Issue: 136(41)

Published: July 19, 2024

Abstract The introduction of precise pore defects into nanocarbon structures results in the emergence distinct physicochemical characteristics. However, there is a lack research on non‐planar chiral nanographene involving defects. Herein, we have developed two analogues to π‐extended pentadecabenzo[9]helicene ( EP9H ) containing embedded Each molecules, namely extended dodecabenzo[7]helicene ED7H ; 1 or nonabenzo[5]helicene EN5H 2 ), exhibits dual‐state emission. Significantly, value | g lum exceptionally high at 1.41×10 −2 solution and B CPL as 254 M −1 cm . In PMMA film, 8.56×10 −3 , powder it 5.00×10 This study demonstrates that molecules with exhibit emission properties while maintaining quite good luminescence properties. It was distinguished from aggregation‐caused quenching (ACQ) effect corresponding without defect. Incorporating also simplifies synthesis process enhances solubility resulting product. These findings suggest can be viable approach improve molecules.

Language: Английский

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Impacts of Heteroatom Substitution on Excited State Dynamics of π-Extended Helicenes

Nanoscale Advances, Journal Year: 2024, Volume and Issue: 6(18), P. 4567 - 4571

Published: Jan. 1, 2024

The excited state dynamics of heterohelicenes [9]TH and [9]AH were spectroscopically studied. showed enhanced fluorescence, while phosphorescence occurred in due to its spin–orbit coupling swift intersystem crossing.

Language: Английский

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