The Aromatic Character of Diindeno[2,1-<i>b</i>:2′,1′-<i>h</i>]biphenylene

Stanger, Amnon

doi:10.1021/acs.orglett.2c00104

Cited by 6 publications

(8 citation statements)

References 21 publications

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“…The best-fit parameters for compound P2 •− with an 14 N hyperfine coupling of 6.4 MHz (0.23 mT) indicate a highly delocalized spin density (Figure 8). 29,41 The theoretical spin density maps further support the delocalization of the unpaired electron (Figure S18). As expected, dianions of A1 and P2 were EPR silent.…”

Section: ■ Results and Discussionmentioning

confidence: 68%

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The Radical Anion and Dianion of Benzo[3,4]cyclobuta[1,2-b]phenazine

Hippchen

Han

et al. 2023

J. Org. Chem.

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We present the reduction of two azaacenes (a benzo-[3,4]cyclobuta[1,2-b]phenazine and a benzo[3,4]cyclobuta[1,2-b]naphtho[2,3-i]phenazine derivative), featuring a single cyclobutadiene unit, to their radical anions and dianions. The reduced species were produced using potassium naphthalenide in the presence of 18-crown-6 in THF. Crystal structures of the reduced representatives were obtained and their optoelectronic properties evaluated. Charging these 4n Hückel systems gives dianionic 4n + 2 π-electron systems with increased antiaromaticity, according to NICS(1.7) zz calculations, featuring unusually red-shifted absorption spectra.

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Section: ■ Results and Discussionmentioning

confidence: 68%

“…In neutral P2 (Figure ), calculated NICS(1.7) zz values are most negative in ring 2 (−24.7 ppm) and increase toward the four-membered ring 6. Compared to benzene (NICS(1.7) zz = −21.6 ppm), ring 5 of the neutral compound is less aromatic (−7.1 ppm).…”

Section: Resultsmentioning

confidence: 99%

The Radical Anion and Dianion of Benzo[3,4]cyclobuta[1,2-b]phenazine

Hippchen

Han

et al. 2023

J. Org. Chem.

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“…Based upon the triplet intensity ratio and equidistant splitting over a total g‐factor of 0.0202 (40 G), we are confident in assigning this signal as a phenyl radical [18] . The presence of a localized phenyl radical means there is a loss of aromaticity, therefore each material undergoes a buckling of the previously planar aromatic rings [23–25] . Importantly, the loss in aromaticity will lead to a disruption in crystalline packing.…”

Section: Resultsmentioning

confidence: 91%

“…Instead, the carbon‐centered radical features appear to be localized, which was evidenced by the sharpness of the peaks. The presence of the localized phenyl radical means there is a loss of aromaticity, therefore each material undergoes a buckling of the previously planar aromatic rings [23–25] . Importantly, the loss in aromaticity disrupts the crystalline packing, leading to decreased crystallinity.…”

Section: Resultsmentioning

confidence: 99%

“…Wu et al and Stanger state that partially resolved hyperfine coupling and asymmetric features paired with highly delocalized carbon-centered radicals lead to this observed spectral feature. [22,23] Therefore, we presume the broad feature present in (4,4'-bpe) • (1,2-C 6 H 6 O 2 ) is due to moderate-to-weak π-π stacking interactions and the intensity of this peak is dependent on the consistency/alignment of the interaction. Additional features are present in the EPR spectra of the cocrystal compared to the single component system, but the decrease in crystallinity is equivalent (74.2 %) upon exposure to radiation in comparison to its single component (74.5 %).In the 1,3-C 6 H 6 O 2 single-component system, 1,3-C 6 H 6 O 2 is connected by hydrogen bonding to form a 2-D network with no additional secondary non-covalent interactions such as π-π stacking (Figure 3b -top).…”

Section: Assessment Of Polyphenol Single-and Multicomponent Systemsmentioning

confidence: 93%

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Atomistic‐Level Effects of Noncovalent Interactions and Crystalline Packing for Organic Material Structural Integrity upon Exposure to Gamma Radiation

Kruse,

Rajapaksha,

MacGillivray

et al. 2023

Chemistry A European J

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Developing an atomistic understanding of ionizing radiation induced changes to organic materials is necessary for intentional design of greener and more sustainable materials for radiation shielding and detection. Cocrystals are promising for these purposes, but a detailed understanding of how the specific intermolecular interactions within the lattice upon exposure to radiation affect the structural stability of the organic crystalline material is unknown. Herein, we report the first study evaluating atomistic‐level effects of γ radiation on both single‐ and multicomponent organic crystalline materials and how specific noncovalent interactions and packing within the crystalline lattice enhance structural stability. Dose studies were performed on all crystalline systems and evaluated via experimental and computational methods. Changes in crystallinity were evaluated by p‐XRD and free radical formation was analyzed via EPR spectroscopy. Type of intermolecular interactions and packing within the crystal lattice was delineated and related to the specific free radical species formed and the structural integrity of each material. Periodic DFT and HOMO‐LUMO surface mapping calculations provided atomistic‐level identifications of the most probable sites for the radicals formed upon exposure to γ radiation and relate intermolecular interactions and molecular packing within the crystalline lattice to experimental results.

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Dithienoazepine‐Based Near‐Infrared Dyes: Janus‐Faced Effects of a Thiophene‐Fused Structure on Antiaromatic Azepines

Murai,

Enoki,

Yamaguchi

2023

Angewandte Chemie

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We here disclose that the incorporation of thiophene rings into a seven‐membered 8π azepine in a fused fashion produces a useful antiaromatic core for near‐infrared (NIR) dyes. In contrast to dibenzazepine derivatives with bent structures, dithieno‐fused derivatives with electron‐accepting groups adopt flat conformations in the ground state. The dithieno‐fused derivatives exhibited broad absorption spectra that cover the visible region as well as sharp emission bands in the NIR region, which are considerably red‐shifted relative to those of the dibenzo‐fused congeners. Theoretical study revealed two contradictory effects of the less‐aromatic thiophene‐fused structure, i.e., the enhancement of the antiaromaticity of the adjacent azepine ring and the relief of the antiaromaticity through the contribution of a quinoidal resonance form. The combination of the dithienoazepine core with cationic electron‐accepting groups produced a NIR fluorescent dye with an emission at 878 nm in solution.

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The Aromatic Character of Diindeno[2,1-b:2′,1′-h]biphenylene

Cited by 6 publications

References 21 publications

The Radical Anion and Dianion of Benzo[3,4]cyclobuta[1,2-b]phenazine

The Radical Anion and Dianion of Benzo[3,4]cyclobuta[1,2-b]phenazine

Atomistic‐Level Effects of Noncovalent Interactions and Crystalline Packing for Organic Material Structural Integrity upon Exposure to Gamma Radiation

Dithienoazepine‐Based Near‐Infrared Dyes: Janus‐Faced Effects of a Thiophene‐Fused Structure on Antiaromatic Azepines

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