A Heptacene Analogue Entailing a Quinoidal Benzodi[7]annulene (7/6/7 Ring) Core with a Tunable Configuration and Multiple Redox Properties

Huang, Yan‐Ying; Wu, Botao; Shi, Dandan; Liú, Dan; Meng, Wei; Ma, Junlong; Qin, Liyuan; Li, Cheng; Zhang, Guanxin; Zhang, Xi‐Sha; Zhang, Deqing

doi:10.1002/anie.202300990

Cited by 16 publications

(4 citation statements)

References 70 publications

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“… 67 The HOMO–LUMO gaps of compounds (IV) and (V) are 1.82 and 1.90 eV, respectively. Coupler (VI) ( 72 ) has 16 π-electrons with a calculated HOMO–LUMO gap of 1.85 eV.…”

Section: Coupler Systemsmentioning

confidence: 99%

Antiaromatic Molecules as Magnetic Couplers: A Computational Quest

Shil,

Bhattacharya,

Misra

et al. 2024

J. Phys. Chem. A

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In this study, we investigate a set of organic diradical structures in which two oxo-verdazyl radicals are selected as radical spin centers that are connected (coupled) via six coupler molecules (CM), resulting in various magnetic (ferromagnetic (FM) or antiferromagnetic (AFM)) characteristics, as reflected by their exchange coupling constants (J). We have designed 12 diradicals with 6-antiaromatic couplers coupled with bis-oxo-verdazyl diradicals with meta−meta (m−m) and para−meta (p−m) positional connectivities. The nature of the magnetic coupling (ferromagnetic, nonmagnetic, or antiferromagnetic) and the magnitude of the exchange constant J depend on the type of coupler, the connecting point between each radical center and CM, the degree of aromaticity of the coupler, and the length of the through-bond distance between radical centers. The computed magnetic exchange coupling constants J for these diradicals at the B3LYP/6-311++G(d,p) and MN12SX/6-311++G(d,p) levels of theory are large for many of these structures, indicating strong ferromagnetic coupling (with positive J values). In some cases, magnetic couplings are observed with J > 1000 cm −1 (B3LYP/6-311++G(d,p)) and strong antiferromagnetic coupling (with negative J values) with J < −1000 cm −1 (B3LYP/6-311++G(d,p)). Similarly, in some cases, magnetic couplings are observed with J > 289 cm −1 (MN12SX/6-311++G(d,p)) and strong antiferromagnetic coupling (with negative J values) with J < −568 cm −1 (MN12SX/6-311++G(d,p)). Furthermore, while numerous studies have reported that the degree of aromaticity of molecular couplers often favors strong ferromagnetic coupling, displaying the high-spin character of diradicals in their ground states, the couplers chosen in this study are characterized as antiaromatic or nonaromatic. The current investigation provides evidence that, remarkably, antiaromatic couplers are able to enhance stability by favoring electronic diradical structures with very strong ferromagnetic coupling when the length of the through-bond distance and connectivity pattern between radical centers are selected in such a way that the FM coupling is optimized. The findings in this study offer new strategies in the design of novel organic materials with interesting magnetic properties for practical applications.

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“… 67 The HOMO–LUMO gaps of compounds (IV) and (V) are 1.82 and 1.90 eV, respectively. Coupler (VI) ( 72 ) has 16 π-electrons with a calculated HOMO–LUMO gap of 1.85 eV.…”

Section: Coupler Systemsmentioning

confidence: 99%

Antiaromatic Molecules as Magnetic Couplers: A Computational Quest

Shil,

Bhattacharya,

Misra

et al. 2024

J. Phys. Chem. A

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“…It is known that the configurations, electronic properties, and bandgaps of nonbenzenoid NGs can be tuned by replacing the 6-membered rings with 5/7-membered rings. The configurations of nonbenzenoid NGs can be planar − or contorted − or curved − or helical, − or nanobelt, or bilayer, depending on the number of nonbenzenoid rings and how these nonbenzenoid rings are incorporated into the NGs. As a result, axially chiral NGs entailing nonbenzenoid rings are expected to show unusual and unique chiral characteristics compared with their benzenoid counterparts.…”

Section: Introductionmentioning

confidence: 99%

Axially Chiral Nonbenzenoid Nanographene with Second Harmonic Generation Property

Qin,

Xie,

et al. 2024

J. Am. Chem. Soc.

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

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“…Among them, the heptagon-based nanographenes usually display negative curvature and form saddle topology. − Meanwhile, the heptagons can stabilize cations through the formation of the 6π-aromatic tropylium cation, leading to the fascinating optoelectronic properties . The first seven-membered-ring-containing nanographene was reported by Yamamoto in 1983. , After that, novel heptagonal-ring embedded arenes have been synthesized via cyclotrimerization and intramolecular cyclization from Scholl reaction and/or under the catalysis of transition metals. − Pyrene and its derivatives are of great concern due to their fascinating optoelectronic properties and ease of modification with various substituents. − When a pyrene unit is fused with nonhexagonal rings, the as-formed curved PAHs might possess a significant enhancement in the functional behavior. The findings stimulated us to design and synthesize such semiconductor materials and realize their promising properties.…”

Section: Introductionmentioning

confidence: 99%

Heptagon-Embedded Helicene Derivatives: Synthesis, Crystal Structural Analyses, and Circularly Polarized Luminescence

Qi,

Shang,

et al. 2023

J. Org. Chem.

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Two pairs of isomers of heptagon-embedded helical arenes (3/6 and 10/13) have been strategically prepared, where the molecular structures of 3 and 13 have been identified through single crystal X-ray diffraction analysis. The effect of the heptagon unit on the physical properties of 3, 6, 10, and 13 is investigated in a comparative manner, and the results indicate that the optical enantiomers of 13 obtained from HPLC exhibit promising chiroptical properties.

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A Heptacene Analogue Entailing a Quinoidal Benzodi[7]annulene (7/6/7 Ring) Core with a Tunable Configuration and Multiple Redox Properties

Cited by 16 publications

References 70 publications

Antiaromatic Molecules as Magnetic Couplers: A Computational Quest

Antiaromatic Molecules as Magnetic Couplers: A Computational Quest

Axially Chiral Nonbenzenoid Nanographene with Second Harmonic Generation Property

Heptagon-Embedded Helicene Derivatives: Synthesis, Crystal Structural Analyses, and Circularly Polarized Luminescence

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