B‐N Covalent Bond Embedded Double Hetero‐[n]helicenes for Pure Red Narrowband Circularly Polarized Electroluminescence with High Efficiency and Stability

Advanced Materials, Journal Year: 2023, Volume and Issue: 36(5)

Published: Sept. 12, 2023

Chiral B/N embedded multi-resonance (MR) emitters open a new paradigm of circularly polarized (CP) organic light-emitting diodes (OLEDs) owing to their unique narrowband spectra. However, pure-red CP-MR and devices remain exclusive in literature. Herein, by introducing B-N covalent bond lower the electron-withdrawing ability para-positioned B-π-B motif, first pair double hetero-[n]helicenes (n = 6 7) emitter peaking 617 nm with small full-width at half-maximum 38 high photoluminescence quantum yield ≈100% toluene is developed. The intense mirror-image CP light produced enantiomers characterized dissymmetry factors (g

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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Polycationic Open‐Shell Cyclophanes: Synthesis of Electron‐Rich Chiral Macrocycles, and Redox‐Dependent Electronic States

Angewandte Chemie International Edition, Journal Year: 2024, Volume and Issue: 63(27)

Published: Feb. 27, 2024

π-Conjugated chiral nanorings with intriguing electronic structures and chiroptical properties have attracted considerable interests in synthetic chemistry materials science. We present the design principles to access new macrocycles (1 2) that are essentially built on key components of main-group electron-donating carbazolyl moieties or π-expanded aza[7]helicenes. Both show unique molecular conformations a (quasi) figure-of-eight topology as result conjugation patterns 2,2',7,7'-spirobifluorenyl 1 triarylamine-coupled aza[7]helicene-based building blocks 2. This nature redox-active, carbazole-rich backbones enabled these be readily oxidized chemically electrochemically, leading sequential production series positively charged polycationic open-shell cyclophanes. Their redox-dependent states resulting multispin polyradicals been characterized by VT-ESR, UV/Vis-NIR absorption spectroelectrochemical measurements. The singlet (ΔE

Language: Английский

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Organic Chameleon: Fluorescence, Phosphorescence and Radical Afterglow Triple Emission from Naphthylimide Functionalized Triphenylphosphine Derivatives

Advanced Functional Materials, Journal Year: 2024, Volume and Issue: 34(21)

Published: Jan. 29, 2024

Abstract Organic radical luminescent materials have attracted worldwide attention because of their absolute spin‐allowed radiative transition and sensitivity to the environment, which give it multiple stimulus response properties. Nowadays, how regulate utilize radicals has become a hot difficult issue. Here, arylphosphonium bromide salts are introduced into molecular backbone naphthimide ( NMI ) using an intramolecular counterion strategy, prepared novel multifunctional stabilized luminescent: TPP‐ o ‐3OMe‐NMI‐Br . Interestingly, this molecule exhibits different assembly modes in solvents, resulting generation two crystals with fluorescence (green: G‐C; orange–yellow: Y‐C), Y‐C crystalline powder excellent stabilization properties for doublet triplet excitons, induce emission orange–yellow afterglow, multi‐stimuli responsiveness external pressure (P), temperature (T) water (W). Moreover, interesting time‐dependent photoactivated colorful afterglow can be observed ‐3OMe‐NMI‐Br@PMMA films doping ratios exhibit multi‐color tunability, responses, data encryption, optical information erase/write behavior. This study not only broadens types applications organic long but also provides new ideas designing “chameleon” field smart luminescence materials.

Language: Английский

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Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(13), P. 9422 - 9433

Published: March 19, 2024

We report a neutral high-spin diradical of chiral C2-symmetric bis[5]diazahelicene with ΔEST ≈ 0.4 kcal mol–1, as determined by EPR spectroscopy/SQUID magnetometry. The is the most persistent among all aminyl radicals reported to date factor 20, half-life up 6 days in 2-MeTHF at room temperature. Its triplet ground state and excellent persistence may be associated unique spin density distribution within dihydrophenazine moiety, which characterizes two effective 3-electron C–N bonds analogous N–O bond nitroxide radical. enantiomerically enriched (ee ≥ 94%) (MM)- (PP)-enantiomers precursors diradicals are obtained either preparative supercritical fluid chromatography or resolution via functionalization auxiliary racemic tetraamine. barrier for racemization solid tetraamine ΔG‡ = 43 ± 0.01 mol–1 483–523 K range. experimentally estimated lower limit diradical, 26 293 K, comparable DFT-determined 31 gas phase 298 K. While pure displays strong chiroptical properties, anisotropy |g| |Δε|/ε 0.036 376 nm, 0.005 548 nm that recently ground-state dication. Notably, radical anion intermediate generation exhibits large SOMO-HOMO inversion, SHI 35 mol–1.

Language: Английский

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Redox-Switchable Aromaticity in a Helically Extended Indeno[2,1-c]fluorene

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(28), P. 19168 - 19176

Published: July 2, 2024

Molecular switches have received major attention to enable the reversible modulation of various molecular properties and been extensively used as trigger elements in diverse fields, including machines, responsive materials, photopharmacology. Antiaromaticity is a fascinating property that has attracted not only significant fundamental interest but also increasingly relevant different applications, particular organic (opto)electronics. However, designing systems which (anti)aromaticity can be judiciously reversibly switched ON OFF remains challenging. Herein, we report helicene featuring an indenofluorene-bridged bisthioxanthylidene novel switch wherein simultaneous two-electron (electro)chemical redox process allows highly its (anti)aromatic character. Specifically, two thioxanthylidene rotors, attached initially aromatic indenofluorene scaffold via overcrowded alkenes, adopt anti-folded structure, upon oxidation convert singly bonded, twisted conformations. This associated with (chir)optical changes importantly results formation fully conjugated, formally antiaromatic as-indacene motif helical core switch. proceeds without buildup radical cation intermediates thus enables switching geometry, aromaticity, absorbance, chiral expression under ambient conditions, evidenced by NMR, UV–vis, CD, (spectro)electrochemical analyses, supported DFT calculations. We expect this concept extendable wide range robust antiaromatic–aromatic provide basis for structure these inherently polycyclic π-scaffolds.

Language: Английский

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Circularly Polarized Luminescence in Macrocycles and Cages: Design, Preparation, and Application

Coordination Chemistry Reviews, Journal Year: 2023, Volume and Issue: 502, P. 215598 - 215598

Published: Dec. 27, 2023

Language: Английский

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A Deep‐Red Emissive Sulfur‐Doped Double [7]Helicene Photosensitizer: Synthesis, Structure and Chiral Optical Properties

Angewandte Chemie International Edition, Journal Year: 2024, Volume and Issue: 63(45)

Published: Aug. 8, 2024

Doping of polycyclic conjugated hydrocarbons (PCHs) with sulfur atoms is becoming more and important as a means creating unique functional materials. Recently, thiophene-containing multiple helicenes have garnered enormous attention due to their intriguing electronic (chir)optical properties compared carbohelicenes. However, the efficient synthesis thiopyran-containing underlying doping mechanisms are rather unexplored. Herein, structural analysis double [7]helicene 3 reported. X-ray crystallographic reveals its dication C

Language: Английский

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Triple para-Functionalized Cations and Neutral Radicals of Enantiopure Diaza[4]helicenes

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(12), P. 8308 - 8319

Published: March 14, 2024

Modulation of absorbance and emission is key for the design chiral chromophores. Accessing a series compounds absorbing emitting (circularly polarized) light over wide spectral window often toward near-infrared practical value in (chir)optical applications. Herein, by late-stage functionalization on derivatives bridging triaryl methyl helicene domains, we have achieved regioselective triple introduction para electron-donating or electron-withdrawing substituents. Extended tuning electronic (e.g., E1/2red −1.50 V → −0.68 V) optical covering from 550 to 850 nm) properties cations neutral radicals; latter being easily prepared mono electron reductions under electrochemical chemical conditions. While luminescence quantum yields can be increased up 70% cationic series, strong Cotton effects are obtained certain radicals at low energies (λabs ∼ 700–900 with gabs values above 10–3. The open-shell nature was further characterized paramagnetic resonance revealing an important spin density delocalization that contributes their persistence.

Language: Английский

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Recent Advances of Boron‐Containing Chiral Luminescent Materials^†

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

Published: Oct. 25, 2024

Comprehensive Summary As a class of organic dyes, boron‐containing compounds play an important role in luminescent materials. They have attracted considerable attention due to their unique photophysical properties. Chiral systems wide range practical applications biological imaging, optoelectronic devices, information storage and 3D display. Boron‐containing chiral materials can not only effectively improve the properties CPL materials, but also bring system, which enables them be used as favorable emitting for expanded applications. Here, we review research progress by detailed discuss according different skeletons, such point chirality, 1,1’‐binaphthyl, [ n ]helicenes, [2,2]paracyclophane pillar[5]arenes. We believe that this is significance development Key Scientists The studies circularly polarized luminescence (CPL) based on small molecules advanced significantly. However, gained recent years. In 2019, Zhao's group prepared binaphthalene derivative modified with triarylborane, representing molecule material exhibit characteristics responsive both solvent fluoride ions. 2020, Chen's steric effects triarylborane triphenylamine prepare planar 2021, Wang's developed new B,N‐embedded double hetero[7]helicenes strong chiroptical responses UV‐visible region. same year, He's asymmetric reactions synthesize boron‐based point‐chirality high efficiency enantioselectivity. 2023, Ravat synthesized 1,4‐B,N‐embedded helicenes exhibiting narrow‐band fluorescence CPL. During period, Matthias Wagner et al obtained (BO) 2 ‐doped tetrathia[7]helicene via efficient four‐step synthesis, Zheng reported nearly pure green electroluminescent device (CP‐OLED). 2024, hetero‐[9]helicenes offering pathway towards significantly enhanced helicene‐based CPEL.

Language: Английский

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