Deep‐Blue Narrowband Hetero[6]helicenes Showing Circularly Polarized Thermally Activated Delayed Fluorescence Toward High‐Performance OLEDs

Advanced Materials, Journal Year: 2023, Volume and Issue: 36(1)

Published: Nov. 14, 2023

Abstract Helicenes exhibit substantial potential as circularly polarized luminescence (CPL) active molecules. However, their application in organic light‐emitting diodes (CP‐OLEDs) is typically hindered by the challenge of integrating both high color purity and efficient triplet‐harvesting capability, particularly blue spectral region. Herein, a series hetero[6]helicene‐based emitters that strategically engineered through helical extension deep‐blue double‐boron‐based multiple resonance thermally activated delayed fluorescence (MR‐TADF) motif, introduced. Importantly, does not cause apparent structural deformation or perturb frontier molecular orbitals; thus, preserving emission MR‐TADF characteristics parent molecule. This approach also leads to reduced reorganization energy, resulting with narrower linewidth higher photoluminescence quantum yield. Further, motif enhances racemization barrier improved CPL performance dissymmetry factor values up 1.5 × 10 −3 . Exploiting these merits, devices incorporating chiral dopants demonstrate within Broadcast Service Television 2020 color‐gamut range, record external efficiencies (EQEs) 29.3%, have distinctive electroluminescence (CPEL) signals. Overall, authors’ findings underscore promising strategy for designing narrowband chiroptical materials advancing high‐definition displays.

Language: Английский

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B,N‐Embedded Hetero[9]helicene Toward Highly Efficient Circularly Polarized Electroluminescence

Angewandte Chemie International Edition, Journal Year: 2024, Volume and Issue: 63(18)

Published: Feb. 21, 2024

The intrinsic helical π-conjugated skeleton makes helicenes highly promising for circularly polarized electroluminescence (CPEL). Generally, carbon undergo low external quantum efficiency (EQE), while the incorporation of a multi-resonance thermally activated delayed fluorescence (MR-TADF) BN structure has led to an improvement. However, reported B,N-embedded all show dissymmetry factors (g

Language: Английский

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Design and enantioselective synthesis of 3D π-extended carbohelicenes for circularly polarized luminescence

Nature Synthesis, Journal Year: 2024, Volume and Issue: 3(6), P. 774 - 786

Published: April 19, 2024

Language: Английский

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π-Extended Helical Multilayer Nanographenes with Layer-Dependent Chiroptical Properties

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(49), P. 26824 - 26832

Published: Dec. 4, 2023

Helical nanographenes (NGs) have attracted increasing attention recently because of their intrinsic chirality and exotic chiroptical properties. However, the efficient synthesis extended helical NGs featuring a multilayer topology is still underdeveloped, layer-dependent properties remain elusive. In this study, we demonstrate modular synthetic strategy to construct series novel (1-3) with through consecutive Diels-Alder reaction regioselective cyclodehydrogenation from readily accessible phenanthrene-based precursors bearing ethynyl groups. The resultant exhibit bilayer, trilayer, tetralayer structures elongated π extension rigid backbones, as unambiguously confirmed by single-crystal X-ray or electron diffraction analysis. We find that photophysical these are notably influenced degree extension, which varies number layers, leading obvious redshifted absorption, fast rising molar extinction coefficient (ε), markedly boosted fluorescence quantum yield (Φf). Moreover, embedded [7]helicene subunits in result stable chirality, enabling both chiral resolution exploration Profiting good alignment electric magnetic dipole moments determined structure, excellent circular dichroism circularly polarized luminescence response unprecedented high CPL brightness up 168 M-1 cm-1, rendering them promising candidates for emitters.

Language: Английский

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Enantioselective synthesis of a two-fold inherently chiral molecular nanographene

Nature Synthesis, Journal Year: 2024, Volume and Issue: 3(4), P. 545 - 553

Published: Feb. 22, 2024

Abstract The introduction and precise control of stereogenic elements in chemical structures is typically a challenging task. Most asymmetric methods require the presence heteroatom starting substrates acting as an anchor point for successful transfer chiral information. For this reason, compounds comprising only carbon atoms, such optically active molecular nanographenes, are usually obtained racemates, isolated by chromatographic separation. Here, we report enantioselective strategy that uses three stereocontrolled synthetic steps to introduce extend different types elements, namely central, axial helicoidal chirality, into polycyclic aromatic structure. Thus, two nanographene layers covalently connected through triindane core. final graphitization Scholl reaction affords formation units with remarkable enantiomeric excesses, high stereochemical stability good chiroptical properties.

Language: Английский

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Nonalternant Nanographenes Containing N-Centered Cyclopenta[ef]heptalene and Aza[7]Helicene Units

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(23), P. 16161 - 16172

Published: May 9, 2024

Introducing helical subunits into negatively curved π-systems has a significant effect on both the molecular geometry and photophysical properties; however, synthesis of these embedded with nonbenzenoid remains challenging due to high strain deriving from curvature helix. Here, we report family nonalternant nanographenes containing nitrogen (N)-doped cyclopenta[ef]heptalene unit. Among them, CPH-2 CPH-3 can be viewed as hybrids benzoannulated aza[7]helicene. The crystal structures revealed saddle for CPH-1, saddle-helix hybrid CPH-2, twist-helix CPH-3. Experimental measurements theoretical calculations indicate that moieties in CPHs undergo flexible conformational changes at room temperature, while aza[7]helicene subunit exhibits dramatically increased racemization energy barrier (78.2 kcal mol–1 143.2 CPH-3). combination lone electron pairs N-doped unit twisted helix fragments results rich photophysics distinctive fluorescence phosphorescence CPH-1 similar Both enantiopure display distinct circular dichroism (CD) signals UV–vis range. Notably, compared reported fully π-extended nanographenes, excellent chiroptical properties |gabs| value 1.0 × 10–2 |glum| 7.0 10–3; values are among highest nanographenes.

Language: Английский

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Enhancing Chiroptical Responses in Helical Nanographenes via Geometric Engineering of Double [7]Helicenes

Angewandte Chemie International Edition, Journal Year: 2024, Volume and Issue: 63(19)

Published: Feb. 19, 2024

Helical nanographenes with high quantum yields and strong chiroptical responses are pivotal for developing circularly polarized luminescence (CPL) materials. Here, we present the successful synthesis of novel π-extended double [7]helicenes (ED7Hs) where two helicene units fused at meta- or para-position middle benzene ring, respectively, as structural isomers reported ortho-fused ED7H. The geometry these ED7Hs is clearly characterized by single-crystal X-ray analysis. Notably, this class exhibits bright exceeding 40 %. Through geometric regulation embedded [7]helicene from ortho-, to para-position, display exceptional amplification in responses. This enhancement evident a remarkable approximate fivefold increase absorbance dissymmetry factors (g

Language: Английский

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Boron‐ and Oxygen‐Doped π‐Extended Helical Nanographene with Circularly Polarised Thermally Activated Delayed Fluorescence

Chemistry - A European Journal, Journal Year: 2024, Volume and Issue: 30(19)

Published: Jan. 25, 2024

Abstract Helical nanographenes have garnered substantial attention owing to their finely adjustable optical and semiconducting properties. The strategic integration of both helicity heteroatoms into the nanographene structure, facilitated by a boron‐oxygen‐based multiple resonance (MR) thermally activated delayed fluorescence (TADF), elevates its photophysical chiroptical features. This signifies introduction an elegant category helical that combines (TADF) (CPL) In this direction, we report synthesis, optical, properties boron, oxygen‐doped Π‐extended nanographene. π‐extension induces distortion in DOBNA‐incorporated nanographene, endowing pair helicenes, ( P)‐ B2NG , M)‐ exhibiting circularly polarized luminescence with g lum −2.3×10 −3 +2.5×10 respectively. exhibited MR‐TADF lifetime below 5 μs, reasonably high quantum yield (50 %). Our molecular design enriches opens up new opportunities multidisciplinary fields.

Language: Английский

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Stable π-Extended Thio[7]helicene-Based Diradical with Predominant Through-Space Spin–Spin Coupling

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(11), P. 7480 - 7486

Published: March 6, 2024

In this work, a novel π-extended thio[7]helicene scaffold was synthesized, where the α-position of thiophene unit could be functionalized with bulky phenoxy radicals after considerable synthetic attempts. This open-shell helical diradical, ET7H-R, possesses high stability in air, nontrivial π conjugation, persistent chirality, and diradical character (y0 0.998). The key feature is predominant through-space spin–spin coupling (TSC) between two at terminals. Variable-temperature continuous-wave electron spin resonance (cw-ESR) superconducting quantum interference device (SQUID) magnetometry solid state reveal singlet ground nearly degenerate triplet ET7H-R. These results highlight significance stable diradicaloid as promising platform for investigating intramolecular TSCs.

Language: Английский

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Axially Chiral Nonbenzenoid Nanographene with Second Harmonic Generation Property

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(17), P. 12206 - 12214

Published: April 18, 2024

Chiral nanographenes (NGs) have garnered significant interest as optoelectronic materials in recent years. While helically chiral NGs been extensively studied, axially only witnessed limited examples, with no prior reports of nonbenzenoid NGs. Herein we report an nanographene featuring six pentagons and four heptagons. This compound, denoted 2, was efficiently synthesized via efficient Pd-catalyzed aryl silane homocoupling reaction. The presence two bulky 3,5-di-tert-butylphenyl groups around the axis connecting PAH (AHR) segments endows 2 atropisomeric chirality high racemization energy barrier, effectively preventing both R- S-enantiomers at room temperature. Optically pure R-2 S-2 were obtained by HPLC separation, they exhibit circular dichroism (CD) activity wavelengths up to 660 nm, one longest CD responses reported for Interestingly, racemic forms a homoconfiguration π-dimer crystal lattice, belonging I222 space group. Consequently, this unique structure renders crystals second harmonic generation (SHG) response, distinguishing it from all benzenoid Moreover, also SHG-CD properties.

Language: Английский

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