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In Silico Screening and Experimental Verification of Near-Infrared-Emissive Two-Boron-Doped Polycyclic Aromatic Hydrocarbons. Angew Chem Int Ed Engl 2024; 63:e202403829. [PMID: 38556467 DOI: 10.1002/anie.202403829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 03/26/2024] [Accepted: 03/27/2024] [Indexed: 04/02/2024]
Abstract
Embedding two boron atoms into a polycyclic aromatic hydrocarbon (PAH) leads to the formation of a neutral analogue that is isoelectronic to the corresponding dicationic PAH skeleton, which can significantly alter its electronic structure. Based on this concept, we explore herein the identification of near-infrared (NIR)-emissive PAHs with the aid of an in silico screening method. Using perylene as the PAH scaffold, we embedded two boron atoms and fused two thiophene rings to it. Based on this design concept, all possible structures (ca. 2500 entities) were generated using a comprehensive structure generator. Time-dependent DFT calculations were conducted on all these structures, and promising candidates were extracted based on the vertical excitation energy, transition dipole moment, and atomization energy per bond. One of the extracted dithieno-diboraperylene candidates was synthesized and indeed exhibited emission at 724 nm with a quantum yield of 0.40 in toluene, demonstrating the validity of this screening method. This modification was further applied to other PAHs, and a series of thienobora-modified PAHs was synthesized.
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2
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U-shaped stereoscopic design strategy toward N-doped nanographene segment. RSC Adv 2024; 14:11771-11774. [PMID: 38617572 PMCID: PMC11009840 DOI: 10.1039/d4ra00788c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 04/09/2024] [Indexed: 04/16/2024] Open
Abstract
There have been scarce reports about stereoscopic design of N-heteroacenes (NHAs), especially for the electron-deficient π-building blocks. Herein, we report the design and synthesis of a U-shaped bis(pyrene-quinoxaline) (BPQ). Single crystal X-ray diffraction reveals the herringbone stacking pattern and the presence of regular and incompletely closed pores.
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3
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BN-Isosteres of Nonacene with Antiaromatic B 2 C 4 and N 2 C 4 Heterocycles: Synthesis and Strong Luminescence. Angew Chem Int Ed Engl 2024; 63:e202316596. [PMID: 38216533 DOI: 10.1002/anie.202316596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 01/11/2024] [Accepted: 01/11/2024] [Indexed: 01/14/2024]
Abstract
Embedding both boron and nitrogen into the backbone of acenes to generate their isoelectronic structures has significantly enriched the acene chemistry to offer appealing properties. However, only small BN-heteroacenes have been extensively investigated, with BN-heptacenes as the hitherto longest homologue. Herein, we report the synthesis of three new nonacene BN-isosteres via incorporating a pair of antiaromatic B2 C4 and N2 C4 heterocycles, representing a new length record for BN-heteroacenes. The distance between the B2 C4 and N2 C4 rings affects the contribution of the charge-separated resonance forms, leading to tunable antiaromaticity of the two heterocycles. The adjusted local antiaromaticity manifests substantial influence on the molecular orbital arrangement, and consequently, the radiative transition rate of BN-3 is greatly enhanced compared with BN-1 and BN-2, realizing a high fluorescence quantum yield of 92 %. This work provides a novel design concept of large acene BN-isosteres and reveals the importance of BN/CC isosterism on their luminescent properties.
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4
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On surface synthesis of an eleven-ring sulfur-doped nonacene. Chem Commun (Camb) 2024; 60:858-861. [PMID: 38131529 DOI: 10.1039/d3cc05486a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Dithienoacenes with a heptacene core, heptaceno[2,3-b:11,12-b']bis[1]benzothiophene, have been synthesized through the combination of solution and surface assisted chemistry. The atomic composition, structural arrangement and electronic properties of the molecules on the Au(111) surface have been deeply explored by non-contact atomic force microscopy (nc-AFM), bond-resolved scanning tunnelling microscopy (BR-STM) and scanning tunneling spectroscopy (STS) corroborated by density functional theory (DFT) calculations. Our combined experiments reveal modifications induced by sulfur substitution.
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5
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Domino-Redox Reaction Induced by An Electrochemically Triggered Conformational Change. Angew Chem Int Ed Engl 2024; 63:e202316753. [PMID: 37971082 DOI: 10.1002/anie.202316753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 11/16/2023] [Accepted: 11/16/2023] [Indexed: 11/19/2023]
Abstract
The concept of a domino-type reaction has been applied in a wide range of fields such as synthetic organic chemistry, material engineering, and life science. To extend the domino concept to redox chemistry, we designed and synthesized a dimeric quinodimethane (QD) with a nonplanar dithiin spacer. The domino-redox properties can be activated by raising the temperature, based on a thermally equilibrated twisted conformation of QD, which has a higher HOMO level that is more readily oxidized. After one QD unit is oxidized (trigger), steric repulsion and electronic interaction between electrophores make the neighboring QD unit adopt a twisted conformation (domino process), which facilitates the following oxidation. Thus, a domino-redox reaction was achieved for the first time by a change in the HOMO level due to a drastic change in the molecular conformation.
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6
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Dark State of the Thiele Hydrocarbon: Efficient Solvatochromic Emission from a Nonpolar Centrosymmetric Singlet Diradicaloid. J Am Chem Soc 2023; 145:20229-20241. [PMID: 37671971 DOI: 10.1021/jacs.3c05251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
In this work, a comprehensive investigation of the photoinduced processes and mechanisms linked to the luminescence of a novel nonperchlorinated Thiele hydrocarbon (TTH) is presented. Despite the comparable diradical character of TTH (y0 = 0.32-0.44) and the unsubstituted Thiele hydrocarbon (TH) (y0 = 0.30), the polyhalogenated species is inert and photostable, showing an intense deep-red/near-infrared (NIR) fluorescence (photoluminescence quantum yield (PLQY) = 0.84 in toluene) even at room temperature and in the solid state (PLQY = 0.19). TTH displays a large Stokes shift (307 nm in benzonitrile) and solvatochromic behavior, which is unusual for a centrosymmetric, nonpolar, and low-conjugated species. These outstanding emission features are interpreted through quantum-chemical calculations, indicating that its fluorescence arises from the low-lying dark doubly excited zwitterionic state, typically found at low excitation energies in diradicaloids, acquiring dipole moment and intensity by state mixing via twisting around the strongly elongated exocyclic CC bonds of the excited p-quinodimethane (pQDM) core, with a mechanism similar to sudden polarization occurring in olefins. Such a mechanism is derived from ns and fs transient absorption measurements.
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7
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Design Strategies for Diradical Boron/Nitrogen Doped Carbon-Based Materials. Angew Chem Int Ed Engl 2023; 62:e202305501. [PMID: 37449378 DOI: 10.1002/anie.202305501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 07/04/2023] [Accepted: 07/13/2023] [Indexed: 07/18/2023]
Abstract
New heterocyclic diradicaloids based on boron and nitrogen-doped polycyclic systems with open-shell ground-states are obtained via concomitant structural and quinoidal extensions, thus allowing to merge the best of both design strategies. A combination of experimental characterization and theoretical calculations have helped disclose their electronic structure, as well as rationalize their associated magnetic and photophysical properties, spanning the chemical space of available molecular templates for cutting-edge applications in organic electronics and spintronics.
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8
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Circumpentacene with Open-Shell Singlet Diradical Character. Angew Chem Int Ed Engl 2023; 62:e202306938. [PMID: 37338045 DOI: 10.1002/anie.202306938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 06/18/2023] [Accepted: 06/19/2023] [Indexed: 06/21/2023]
Abstract
Circumacenes (CAs) are a distinctive type of benzenoid polycyclic aromatic hydrocarbons where an acene unit is completely enclosed by a layer of outer fused benzene rings. Despite their unique structures, the synthesis of CAs is challenging, and until recently, the largest CA molecule synthesized was circumanthracene. In this study, we report the successful synthesis of an extended circumpentacene derivative 1, which represents the largest CA molecule synthesized to date. Its structure was confirmed by X-ray crystallographic analysis and its electronic properties were systematically investigated by both experiments and theoretical calculations. It shows a unique open-shell diradical character due to the existence of extended zigzag edges, with a moderate diradical character index (y0 =39.7 %) and a small singlet-triplet energy gap (ΔES-T =-4.47 kcal/mol). It exhibits a dominant local aromatic character with π-electrons delocalized in the individual aromatic sextet rings. It has a small HOMO-LUMO energy gap and displays amphoteric redox behavior. The electronic structures of its dication and dianion can be considered as doubly charged structures in which two coronene units are fused with a central aromatic benzene ring. This study provides a new route toward stable multizigzag-edged graphene-like molecules with open-shell di/polyradical character.
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9
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Bisazapentalene Dication: Global Aromaticity and Open-Shell Singlet Ground State. Org Lett 2023; 25:3380-3385. [PMID: 37162270 DOI: 10.1021/acs.orglett.3c00870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Antiaromatic moieties fused in polycyclic π-conjugated molecules usually exhibit strong localized antiaromaticiy. Herein, we reported the synthesis and properties of a bisazapentalene dication (BAP2+) obtained from in situ two-electron oxidation of neutral species 8. Noteworthily, it possesses global aromaticity and an open-shell singlet ground state. This study underlines the importance of heteroatoms in determining the delocalization of π-electrons and the aromaticity of molecules in their oxidized states.
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10
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Closed-shell and open-shell dual nature of singlet diradical compounds. PURE APPL CHEM 2023. [DOI: 10.1515/pac-2023-0114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
Abstract
Unlike triplet diradicals, singlet diradicals can vary in diradical character from 0 % to 100 % depending on linker units that allow two formally unpaired electrons to couple covalently. In principle, the electronic structure of singlet diradicals can be described as a quantum superposition of closed-shell and open-shell structures. This means that, depending on the external environment, singlet diradicals can behave as either closed-shell or open-shell species. This paper summarizes our progress in understanding the electronic structure of π-conjugated singlet diradical molecules in terms of closed-shell and open-shell dual nature. We first discuss the coexistence of intra- and intermolecular covalent bonding interactions in the π-dimer of a singlet diradical molecule. The intra- and intermolecular coupling of two formally unpaired electrons are related to closed-shell and open-shell nature of singlet diradical, respectively. Then we demonstrate the coexistence of the covalent bonding interactions in the one-dimensional stack of singlet diradical molecules having different diradical character. The relative strength of the interactions is varied with the magnitude of singlet diradical index y
0. Finally, we show the dual reactivity of a singlet diradical molecule, which undergoes rapid [4 + 2] and [4 + 4] cycloaddition reactions in the dark at room temperature. Closed-shell and open-shell nature endow the singlet diradical molecule with the reaction manner as diene and diradical species, respectively.
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11
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Diradical B/N-Doped Polycyclic Hydrocarbons. Angew Chem Int Ed Engl 2023; 62:e202217470. [PMID: 36599802 DOI: 10.1002/anie.202217470] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 01/04/2023] [Accepted: 01/04/2023] [Indexed: 01/06/2023]
Abstract
Heterocyclic diradicaloids with atom-precise control over open-shell nature are promising materials for organic electronics and spintronics. Herein, we disclose quinoidal π-extension of a B/N-heterocycle for generating B/N-type organic diradicaloids. Two quinoidal π-extended B/N-doped polycyclic hydrocarbons that feature fusion of the B/N-heterocycle motif with the antiaromatic s-indacene or dicyclopenta[b,g]naphthalene core were synthesized. This quinoidal π-extension and B/N-heterocycle leads to their open-shell electronic nature, which stands in contrast to the multiple-resonance effect of conventional B/N-type emitters. These B/N-type diradicaloids have modulated (anti)aromaticity and enhanced diradical characters comparing with the all-carbon analogues, as well as intriguing properties, such as magnetic activities, narrow energy gaps and highly red-shifted absorptions. This study thus opens the new space for both of B/N-doped polycyclic π-systems and heterocyclic diradicaloids.
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12
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Furan-Extended Helical Rylenes with Fjord Edge Topology and Tunable Optoelectronic Properties. Angew Chem Int Ed Engl 2023; 62:e202214653. [PMID: 36470852 DOI: 10.1002/anie.202214653] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 12/02/2022] [Accepted: 12/05/2022] [Indexed: 12/12/2022]
Abstract
Lateral furan-expansion of polycyclic aromatics, which enables multiple O-doping and peripheral edge evolution of rylenes, is developed for the first time. Tetrafuranylperylene TPF-4CN and octafuranylquaterrylene OFQ-8CN were prepared as model compounds bearing unique fjord edge topology and helical conformations. Compared to TPF-4CN, the higher congener OFQ-8CN displays a largely red-shifted (≈333 nm) and intensified absorption band (λmax =829 nm) as well as a narrowed electrochemical band gap (≈1.08 eV) due to its pronounced π-delocalization and emerging of open-shell diradicaloid upon the increase of fjord edge length. Moreover, strong circular dichroism signals in a broad range until 900 nm are observed for open-shell chiral OFQ-8CN, owing to the excellent conformational stability of its central bis(tetraoxa[5]helicene) fragments. Our studies provide insights into the relationships between edge topologies and (chir)optoelectronic properties for this novel type of O-doped PAHs.
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13
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Design of an open-shell nitrogen-centered diradicaloid with tunable stimuli-responsive electronic properties. Commun Chem 2022; 5:127. [PMID: 36697916 PMCID: PMC9814612 DOI: 10.1038/s42004-022-00747-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 10/03/2022] [Indexed: 01/28/2023] Open
Abstract
Organic diradicaloids usually display an open-shell singlet ground state with significant singlet diradical character (y0) which endow them with intriguing physiochemical properties and wide applications. In this study, we present the design of an open-shell nitrogen-centered diradicaloid which can reversibly respond to multiple stimuli and display the tunable diradical character and chemo-physical properties. 1a was successfully synthesized through a simple and high-yielding two-step synthetic strategy. Both experimental and calculated results indicated that 1a displayed an open-shell singlet ground state with small singlet-triplet energy gap (ΔES-T = -2.311 kcal mol-1) and a modest diradical character (y0 = 0.60). Interestingly, 1a was demonstrated to undergo reversible Lewis acid-base reaction to form acid-base adducts, which was proven to effectively tune the ground-state electronic structures of 1a as well as its diradical character and spin density distributions. Based on this, we succeeded in devising a photoresponsive system based on 1a and a commercially available photoacid merocyanine (MEH). We believe that our studies including the molecular design methodology and the stimuli-responsive organic diradicaloid system will open up a new way to develop organic diradicaloids with tunable properties and even intelligent-responsive diradicaloid-based materials.
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14
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π-Extended S-Heterocyclic Naphthoquinodimethane with Dual Diradical and Dipolar Character. Org Lett 2022; 24:5935-5940. [PMID: 35938992 DOI: 10.1021/acs.orglett.2c02188] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The 2,6-naphthoquinodimethane (2,6-NQDM) containing S-heterocyclic molecule 6-S was synthesized, and its dual open-shell diradical and dipolar characters were revealed via both experimental and theoretical studies. Unlike the shorter p-quinodimethane (p-QDM)-containing analogue 5-S, which possesses a closed-shell ground state (y0 = 0%) with small dipolar character, 6-S possesses enhanced dipolar character with a singlet diradical ground state (y0 = 23.3%) and a thermally accessible triplet excited state (ΔEST = -4.13 kcal/mol). Despite this, it displays good stability (t1/2 = 41days) under ambient air and light conditions due to its distinctive dipolar character and kinetic blocking of reactive sites.
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15
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Pushing the Length Limit of Dihydrodiboraacenes: Synthesis and Characterizations of Boron-Embedded Heptacene and Nonacene. Angew Chem Int Ed Engl 2022; 61:e202200779. [PMID: 35253330 DOI: 10.1002/anie.202200779] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Indexed: 12/24/2022]
Abstract
Boron-embedded heteroacenes (boraacenes) have attracted enormous interest in organic chemistry and materials science. However, extending the skeleton of boraacenes to higher acenes (N≥6) is synthetically challenging because of their limited stability under ambient conditions. Herein, we report the synthesis of boron-embedded heptacene (DBH) and nonacene (DBN) as the hitherto longest boraacenes. The former is highly stable (even after 240 h in tetrahydrofuran), while the latter is air-sensitive with the half-life (t1/2 ) of 11.8 min. The structures of both compounds are verified by single-crystal X-ray diffraction, revealing a linear backbone with an antiaromatic C4 B2 core. Photophysical characterizations associated with theoretical calculations indicate that both compounds exhibit highly efficient anti-Kasha emissions. Remarkably, the air-stable DBH manifests an ultrahigh photoluminescence quantum yield (PLQY) of 98±2 % and can be chemically reduced to its radical anion and dianion states, implying the value of boron-doped higher acenes as novel functional materials.
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16
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Tuning Diradical Properties of Boron-Containing π-Systems by Structural Isomerism. Chemistry 2022; 28:e202200045. [PMID: 35146820 DOI: 10.1002/chem.202200045] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Indexed: 01/01/2023]
Abstract
Tuning diradical character is an important topic for organic diradicaloids. Herein, we report the precise borylation enabling structural isomerism as an effective strategy to modulate diradical character and thereby properties of organic diradicaloids. We synthesized a new B-containing polycyclic hydrocarbon that has the indeno[1,2-b]fluorene π-skeleton with the β-carbons bonding to two boron atoms. Detailed theoretical and experimental results show that this bonding pattern leads to its distinctive electronic structures and properties in comparison to that of its isomeric molecule. This molecule has the efficient conjugation between boron atoms and π-skeleton, resulting in downshifted LUMO and HOMO levels. Moreover, it exhibits smaller diradical character and thereby inhibited diradical properties, such as significantly blue-shifted light absorption, larger energy bandgap and weak para-magnetic resonance. Notably, this B-containing polycyclic hydrocarbon possesses much stronger Lewis acidity and its Lewis acid-base adducts display enhanced diradical character, demonstrating the positive effects of Lewis coordination on modulating diradical performance.
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Pushing the Length Limit of Dihydrodiboraacenes: Synthesis and Characterizations of Boron‐Embedded Heptacene and Nonacene. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202200779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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18
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The catenation of a singlet diradical dication and modulation of diradical character by metal coordination. Chem Commun (Camb) 2022; 58:6457-6460. [DOI: 10.1039/d2cc01539k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A singlet bis(triarylamine) diradical dication and its zigzag 1D magnetic chain catenated by silver cations were isolated and characterized by single-crystal X-ray crystallography, EPR spectroscopy, SQUID measurements, cyclic voltammetry and...
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19
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Doubly-Reduced Pentacene in Different Coordination Environments: X-ray Crystallographic and Theoretical Insights into Structural and Electronic Changes. Chemistry 2021; 28:e202104194. [PMID: 34890088 DOI: 10.1002/chem.202104194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Indexed: 11/11/2022]
Abstract
Chemical reduction of pentacene (C22H14, 1) with Group 1 metals ranging from Li to Cs revealed that 1 readily undergoes a two-fold reduction to afford a doubly-reduced 12- anion in THF. With the help of 18-crown-6 ether used as a secondary coordinating agent, five π-complexes of 12- with different alkali metal counterions have been isolated and fully characterized. This series of complexes enables the first evaluation of alkali-metal ion binding patterns and structural changes of the 12- dianion based on the crystallographically confirmed examples. The difference in coordination of the smallest Li+ ion vs. heavier Group 1 congeners has been demonstrated. In addition, the use of benzo-15-crown-5 in the reaction of 1 with Na metal allowed the isolation of the unique solvent-separated ion product with a "naked" dianion, 12-. The detailed structural analyses of the series revealed the C-C bond alteration and core deformation of pentacene upon two-fold reduction and complexation. The negative charge localization at the central six-membered ring of 12- identified by theoretical calculations corroborates with the X-ray crystallographic results. Subsequent in-depth theoretical analysis provided a detailed description of changes in the electronic structure and aromaticity of pentacene upon reduction.
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20
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Boron-Containing Organic Diradicaloids: Dynamically Modulating Singlet Diradical Character by Lewis Acid-Base Coordination. J Am Chem Soc 2021; 143:18272-18279. [PMID: 34664955 DOI: 10.1021/jacs.1c08486] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Organic diradicaloids have unique open-shell structures and properties and promising applications in organic electronics and spintronics. Incorporation of heteroatoms is an effective strategy to alter the electronic structures of organic diradicaloids. However, B-containing organic diradicaloids are very challenging due to their high reactivities, which are caused by not only diradical nature but also the B atom. In this article, we report a new kind of organic diradicaloids containing boron atoms. Our strategy is to incorporate planarized triarylboranes to antiaromatic polycyclic hydrocarbons (PHs). We synthesized two isomeric B-containing PHs composed of indenofluorene π-skeletons and two dioxa-bridged triphenylborane moieties. As proved by theoretical and experimental results, both of them have excellent ambient stability and open-shell singlet diradical structures, as well as intriguing magnetic and optoelectronic properties, such as thermally accessible triplet species, reversible multiredox ability, and narrow energy gaps. Notably, they possess sufficient Lewis acidity, which has never been observed for organic diradicaloids. In addition, they can coordinate with Lewis bases to form Lewis adducts, achieving unprecedented dynamic modulations of (anti)aromaticity and thus diradical character of organic diradicaloids.
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21
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Electron-Deficient Heteroacenes that Contain Two Boron Atoms: Near-Infrared Fluorescence Based on a Push-Pull Effect*. Angew Chem Int Ed Engl 2021; 60:21853-21859. [PMID: 34115434 DOI: 10.1002/anie.202106642] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Indexed: 12/20/2022]
Abstract
Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push-pull effect along the long axis of the molecule derived from the electron-donating ether moieties and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm-1 in cyclohexane. A Franck-Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.
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22
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Electron‐Deficient Heteroacenes that Contain Two Boron Atoms: Near‐Infrared Fluorescence Based on a Push–Pull Effect**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202106642] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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23
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The Contribution of Density Functional Theory to the Atomistic Knowledge of Electrochromic Processes. Molecules 2021; 26:molecules26195793. [PMID: 34641338 PMCID: PMC8510163 DOI: 10.3390/molecules26195793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 09/08/2021] [Accepted: 09/19/2021] [Indexed: 11/29/2022] Open
Abstract
In this review, we provide a brief overview of the contribution that computational studies can offer to the elucidation of the electronic mechanisms responsible for the electrochromism phenomenon, through the use of the density functional theory (DFT) and its time-dependent formulation (TDDFT). Although computational studies on electrochromic systems are not as numerous as those for other physico-chemical processes, we will show their reliability and ability to predict structures, excitation energies, and redox potentials. The results confirm that these methods not only help in the interpretation of experimental data but can also be used for the rational design of molecules with interesting electrochromic properties to be initiated for synthesis and experimental characterization.
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Spin–Spin Interactions in One‐Dimensional Assemblies of a Cumulene‐Based Singlet Biradical. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202105740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Spin-Spin Interactions in One-Dimensional Assemblies of a Cumulene-Based Singlet Biradical. Angew Chem Int Ed Engl 2021; 60:21319-21326. [PMID: 34101316 DOI: 10.1002/anie.202105740] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Indexed: 11/09/2022]
Abstract
The synthesis of phenalenyl-endcapped [5]cumulene as a cumulene-based singlet biradical and the spin correlation changes of one-dimensional aggregates are described. The high propensity for self-aggregation of phenalenyl rings and the introduction of bulky substituents into the appropriate positions led to the formation of a one-dimensional chain assembly. Single-crystal X-ray structural analysis indicated that the bond length alternation of the cumulene chain increased with decreasing temperature, along with improved overlapping of the phenalenyl rings. Variable-temperature Raman spectroscopy and magnetic susceptibility measurements revealed that a localized spin pair within the molecule decouples at low temperatures, and a continuum spin system involving intra- and intermolecular spin-spin interactions emerges in the one-dimensional chain.
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Cascade Oxidative C−H Annulation of Thiophenes: Heck‐Type Pathway Enables Concise Access to Thienoacenes. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202103160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Cascade Oxidative C-H Annulation of Thiophenes: Heck-Type Pathway Enables Concise Access to Thienoacenes. Angew Chem Int Ed Engl 2021; 60:12371-12375. [PMID: 33759335 DOI: 10.1002/anie.202103160] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Indexed: 02/02/2023]
Abstract
The pursuit of efficient synthetic route to thienoacenes represents an appealing yet challenging task in the fields of both organic synthetic chemistry and organic functional materials. In this work, we disclose a rhodium-catalyzed cascade C-H annulation of phenacyl phosphoniums with (benzo)thiophenes via a Heck-type pathway to provide a new class of planar thienoacenes, which involves the formation of three Caryl -Caryl bonds and one Caryl -O bond in a single operation. The neutral S,O-heteroacenes exhibit superior stability and adopt a herringbone-like packing mode with efficient π-π stacking in the crystals, suggesting their potential in organic semiconducting materials. This work first exemplifies the superiority of cascade oxidative C-H annulation involving a Heck-type pathway in the development of concise access to heteroacenes.
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A Tetraindeno-Fused Bis(anthraoxa)quinodimethane with Nine Consecutively Fused Six-Membered Rings. Org Lett 2021; 23:3027-3031. [PMID: 33819423 DOI: 10.1021/acs.orglett.1c00705] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A tetraindeno-fused bis(anthraoxa)quinodimethane RBR with nine consecutively fused six-membered rings in a row was synthesized. Its structure was confirmed by X-ray crystallographic analysis and NMR measurement. Compared with an unfused analogue ABA, the indeno fusion onto the zigzag edges not only enhanced the photostability but also dramatically tuned the electronic properties. Due to the existence of two rubicene units, RBR can also be readily reduced to form a radical anion and dianion.
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Synthesis of a Highly Fluorescent Bis(1,4-oxaborine)pentacene. Chempluschem 2021; 86:836-839. [PMID: 33861901 DOI: 10.1002/cplu.202100098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/31/2021] [Indexed: 12/30/2022]
Abstract
1,4-Oxaborines represent an expansion of the current array of heteroborines. Herein, we report a new ladder-type bis(1,4-oxaborine)pentacene (BO-Pen), the backbone of which can be regarded as an isoelectronic structure of pentacene. The synthesis begins with a two-fold nucleophilic aromatic substitution followed by a ring-closing reaction. The structure was confirmed by X-ray crystallographic analysis. Compound BO-Pen is stable (even after 160 h) under ambient condition and exhibits very different electronic properties as compared to its all-carbon pentacene analogue (Pen-M). Particularly, it shows bright photoluminescence (73 % relative quantum yield) in both solution and in solid state.
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Rational design and syntheses of aniline-based diradical dications: isolable congeners of quinodimethane diradicals. Org Chem Front 2021. [DOI: 10.1039/d0qo01265c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two-electron oxidation of five aniline-based compounds 4,4′′-p/m-terphenyldiamines afforded the first isolable aniline-based diradical dications 12+–52+.
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S‐shaped
para
‐Quinodimethane‐Embedded Double [6]Helicene and Its Charged Species Showing Open‐Shell Diradical Character. Chemistry 2020; 26:15613-15622. [DOI: 10.1002/chem.202002952] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Indexed: 01/05/2023]
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Abstract
Thiele, Chichibabin and Müller hydrocarbons are considered as classical Kekulé diradicaloids. Herein we report the synthesis and characterization of acyclic diaminocarbene (ADC)-based Thiele, Chichibabin, and Müller hydrocarbons. The calculated singlet–triplet energy gaps are ΔES–T = −27.96, −3.70, −0.37 kcal mol−1, respectively, and gradually decrease with the increasing length of the π-conjugated spacer (p-phenylene vs. p,p′-biphenylene vs. p,p′′-terphenylene) between the two ADC-scaffolds. In agreement with the calculations, we also experimentally observed the enhancement of paramagnetic diradical character as a function of the length of the π-conjugated spacer. ADC-based Thiele's hydrocarbon is EPR silent and exhibits very well resolved NMR spectra, whereas ADC-based Müller's hydrocarbon displays EPR signals and featureless NMR spectra at room temperature. The spacer also has a strong influence on the UV-Vis-NIR spectra of these compounds. Considering that our methodology is modular, these results provide a convenient platform for the synthesis of an electronically modified new class of carbon-centered Kekulé diradicaloids. We report the synthesis of acyclic diaminocarbene (ADC)-scaffold based Thiele, Chichibabin, and Müller hydrocarbons. Studies support that the singlet-triplet energy gap depends on the π-conjugated spacer between the ADC scaffolds.![]()
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Abstract
Quinoidal azaacenes with almost pure diradical character (y=0.95 to y=0.99) were synthesized. All compounds exhibit paramagnetic behavior investigated by EPR and NMR spectroscopy, and SQUID measurements, revealing thermally populated triplet states with an extremely low-energy gap ΔEST' of 0.58 to 1.0 kcal mol-1 . The species are persistent in solution (half-life≈14-21 h) and in the solid state they are stable for weeks.
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Crystalline Diradical Dianions of Pyrene-Fused Azaacenes. Angew Chem Int Ed Engl 2020; 59:11794-11799. [PMID: 32304152 DOI: 10.1002/anie.202001842] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Indexed: 01/09/2023]
Abstract
Although diradicals and azaacenes have been greatly attractive in fundamental chemistry and functional materials, the isolable diradical dianions of azaacenes are still unknown. Herein, we describe the first isolation of pyrene-fused azaacene diradical dianion salts [(18-c-6)K(THF)2 ]+ [(18-c-6)K]+ ⋅12-.. and [(18-c-6)K(THF)]2+ ⋅22-.. by reduction of the neutral pyrene-fused azaacene derivatives 1 and 2 with excess potassium graphite in THF in the presence of 18-crown-6. Their electronic structures were investigated by various experiments, in conjunction with theoretical calculations. It was found that both dianions are open-shell singlets in the ground state and their triplet states are thermally readily accessible owing to the small singlet-triplet energy gap. This work provides the first examples of crystalline diradical dianions of azaacenes with considerable diradical character.
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Diindenoanthracene Diradicaloids Enable Rational, Incremental Tuning of Their Singlet-Triplet Energy Gaps. Chem 2020. [DOI: 10.1016/j.chempr.2020.02.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Recent Progress in High Linearly Fused Polycyclic Conjugated Hydrocarbons (PCHs, n > 6) with Well-Defined Structures. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:1903766. [PMID: 32596114 PMCID: PMC7312318 DOI: 10.1002/advs.201903766] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 03/17/2020] [Indexed: 05/05/2023]
Abstract
Although polycyclic conjugated hydrocarbons (PCHs) and their analogues have gained great progress in the fields of organic photoelectronic materials, the in-depth study on present PCHs is still limited to hexacene or below because longer PCHs are insoluble, unstable, and tediously synthesized. Very recently, various strategies including on-surface synthesis are developed to address these issues and many higher novel PCHs are constructed. Therefore, it is necessary to review these advances. Here, the recent synthetic approach, basic physicochemical properties, single-crystal packing behaviors, and potential applications of the linearly fused PCHs (higher than hexacene), including acenes or π-extended acenes with fused six-membered benzenoid rings and other four-membered, five-membered or even seven-membered and eight-membered fused compounds, are summarized.
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O-Annulation to Polycyclic Aromatic Hydrocarbons: A Tale of Optoelectronic Properties from Five- to Seven-Membered Rings. Org Lett 2020; 22:4283-4288. [PMID: 32429668 DOI: 10.1021/acs.orglett.0c01331] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We take advantage of the Pummerer oxidative annulation reaction to extend PAHs through the formation of an intramolecular C-O bond with a suitable phenol substituent. Depending on the peripheral topology of the PAH precursor (e.g., pyrene, boron-dipyrromethene, or perylene diimide) five-, six-, and seven-membered O-containing rings could be obtained. The effect of the O-annulations on the optoelectronic properties were studied by various methods with the pyrano-annulated pyrene and BODIPY derivatives depicting quantitative emission quantum yields.
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Duality of Reactivity of a Biradicaloid Compound with an o-Quinodimethane Scaffold. J Am Chem Soc 2020; 142:5408-5418. [DOI: 10.1021/jacs.0c01003] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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O‐Doped Nanographenes: A Pyrano/Pyrylium Route Towards Semiconducting Cationic Mixed‐Valence Complexes. Angew Chem Int Ed Engl 2020; 59:4106-4114. [DOI: 10.1002/anie.201914025] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Revised: 12/26/2019] [Indexed: 12/14/2022]
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O‐Doped Nanographenes: A Pyrano/Pyrylium Route Towards Semiconducting Cationic Mixed‐Valence Complexes. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201914025] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Abstract
A series of quinoidal N,N'-diaryldiaza-N,N'-dihydropentacenes (Quino) was prepared in a two-step reaction, starting from quinacridone. Oxidation of Quino furnishes stable radical cations, isoelectronic to the radical anions of the azaacenes, whereas the dicationic species are isoelectronic to neutral azapentacenes. The spectroscopic properties of the diaryldiazapentacenes and their oxidized mono- and dications are equivalent to that of the dianion of tetraazapentacene (TAP), its radical anion and the neutral TAP.
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New fused conjugated molecules with fused thiophene and pyran units for organic electronic materials. RSC Adv 2020; 10:12378-12383. [PMID: 35497610 PMCID: PMC9050829 DOI: 10.1039/d0ra01984d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 03/06/2020] [Indexed: 12/22/2022] Open
Abstract
Rigid and planar conjugated molecules have substantial significance due to their potential applications in organic electronics. Herein we report two highly fused ladder type conjugated molecules, TTCTTC and TTTCTTTC, with up to 10 fused rings in which the fused-thiophene rings are fused to the chromeno[6,5,4-def]chromene unit. Both molecules show high HOMO levels and accordingly they can be oxidized into their radical cations with absorptions extending to 1300 nm in the presence of trifluoroacetic acid. Thin films of TTCTTC and TTTCTTTC exhibit p-type semiconductor properties with hole mobilities up to 0.39 cm2 V−1 s−1. Moreover, TTCTTC shows a high fluorescence quantum yield of up to 16.5% in the solid state. Fused conjugated molecules TTCTTC and TTTCTTTC with up to ten heterocycles were constructed by fusing fused-thiophene to the chromeno[6,5,4-def]chromene unit.![]()
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Open-shell singlet diradicaloid difluoreno[4,3-b:3′,4′-d]furan and its radical cation and dianion. Chem Commun (Camb) 2020; 56:5881-5884. [DOI: 10.1039/d0cc01638a] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We report difluoreno[4,3-b:3′,4′-d]furan derivative as a stable open-shell singlet diradicaloid.
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Dynamic solvent effects in radical-radical coupling reactions: an almost bottleable localised singlet diradical. Phys Chem Chem Phys 2020; 22:27949-27954. [PMID: 33184617 DOI: 10.1039/d0cp05235c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Localised singlet diradicals are key intermediates in bond homolysis, which plays a crucial role in chemical reactions. However, thorough experimental analyses of the reaction dynamics and chemical properties are generally difficult because bond formation is rapid, even under low-temperature matrix conditions. In this study, the effects of solvent and pressure on the lifetimes of long-lived singlet diradicals with bulky substituents were investigated. The solvent dynamic effect was revealed to provide control over the rate constant of radical-radical coupling reactions, and an almost bottleable singlet diradical with a lifetime of ∼2 s at 293 K was obtained.
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Open-Shell Effects on Optoelectronic Properties: Antiambipolar Charge Transport and Anti-Kasha Doublet Emission from a N-Substituted Bisphenalenyl. J Am Chem Soc 2019; 142:38-43. [DOI: 10.1021/jacs.9b10677] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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50
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Tunable Reduction of 2,4,6‐Tri(4‐pyridyl)‐1,3,5‐Triazine: From Radical Anion to Diradical Dianion to Radical Metal–Organic Framework. Angew Chem Int Ed Engl 2019; 58:18224-18229. [DOI: 10.1002/anie.201910468] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 09/19/2019] [Indexed: 11/06/2022]
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