π‐Extended Helical Nanographenes: Synthesis and Photophysical Properties of Naphtho[1,2‐<i>a</i>]pyrenes**

Chalifoux, Wesley A.; Sitaula, Paban; Malone, Ryan; Longhi, Giovanna; Abbate, Sergio; Gualtieri, Eva; Lucotti, Andrea; Tommasini, Matteo; Franzini, Roberta; Villani, Claudio; Catalano, Vincent J.

doi:10.1002/ejoc.202101466

Cited by 4 publications

(4 citation statements)

References 60 publications

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“…Unfortunately, the fluorescence quantum yield of 7c was too low to obtain CPL data. These values compare favorably to those reported for other highly contorted, chiral organic compounds. ,,,,− …”

supporting

confidence: 82%

“…In recent years, our groups have reported the synthesis of chiral perylene bisimides and structurally related chiral peropyrenes. − The latter were synthesized via 4-fold alkyne benzannulation (Figure a) wherein the bay regions of the peropyrene are functionalized by bulky aryl groups, creating a barrier to racemization that is sufficient for the separation of enantiomers by chiral HPLC. More recently, the Nevada team reported the use of alkyne benzannulation to laterally expand the π-electron systems of [4]helicenes while functionalizing the resulting cove regions (Figure b,c). , This functionalization increases the barrier of enantiomerization well beyond that of normal [4]helicene, allowing for the separation and analysis of enantiomers.…”

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confidence: 99%

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Synthesis and Properties of Achiral and Chiral Dipyrenoheteroles and Related Compounds

et al. 2023

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Achiral and chiral isomers of dipyrenoheteroles were synthesized via alkyne benzannulation. The electronic properties of these compounds were examined using cyclic voltammetry and differential pulse voltammetry. The enantiomers of the chiral isomers were separated, and their optical properties were examined in circular dichroism and circularly polarized luminescence studies. The chiral isomers exhibited a large bathochromic shift, relative to the achiral isomer, in both absorbance and fluorescence, resulting from decreased symmetry, rather than a change in the size of the backbone.

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confidence: 82%

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confidence: 99%

Synthesis and Properties of Achiral and Chiral Dipyrenoheteroles and Related Compounds

et al. 2023

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“…Helicenes are helically shaped chiral polycyclic aromatic compounds. − Their inherent twist originates from their intramolecular steric demands and leads to special optical and electronic properties, − in comparison to their nontwisted counterparts. Deviations from planarity are generally associated with geometric distortions and with increased strain in these polycyclic structures.…”

Section: Resultsmentioning

confidence: 99%

Localized Antiaromaticity Hotspot Drives Reductive Dehydrogenative Cyclizations in Bis- and Mono-Helicenes

Zhou

Egger

et al. 2022

J. Am. Chem. Soc.

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We describe reductive dehydrogenative cyclizations that form hepta-, nona-, and decacyclic anionic graphene subunits from mono-and bis-helicenes with an embedded five-membered ring. The reaction of bis-helicenes can either proceed to the full double annulation or be interrupted by addition of molecular oxygen at an intermediate stage. The regioselectivity of the interrupted cyclization cascade for bishelicenes confirms that relief of antiaromaticity is a dominant force for these facile ring closures. Computational analysis reveals the unique role of the preexisting negatively charged cyclopentadienyl moiety in directing the second negative charge at a specific remote location and, thus, creating a localized antiaromatic region. This region is the hotspot that promotes the initial cyclization. Computational studies, including MO analysis, molecular electrostatic potential maps, and NICS(1.7) ZZ calculations, evaluate the interplay of the various effects including charge delocalization, helicene strain release, and antiaromaticity. The role of antiaromaticity relief is further supported by efficient reductive closure of the less strained monohelicenes where the relief of antiaromaticity promotes the cyclization even when the strain is substantially reduced. The latter finding significantly expands the scope of this reductive alternative to the Scholl ring closure.

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“…Helicenes are helically shaped chiral polycyclic aromatic compounds. [48][49][50][51][52][53][54][55] Their inherent twist originates from their intramolecular steric demands and leads to special optical and electronic properties, [56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73] in comparison to their non-twisted counterparts. Deviations from planarity are generally associated with geometric distortions and with increased strain in these polycyclic structures.…”

Section: Resultsmentioning

confidence: 99%

Localized Antiaromaticity Hot-spot Drives Reductive Dehydrogenative Cyclizations in Bis- and Mono-Helicenes

Zhou

Egger

et al. 2022

Preprint

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We describe reductive dehydrogenative cyclizations that form hepta-, nona- and decacyclic anionic graphene subunits from mono- and bis-helicenes with an embedded five-membered ring. The reaction of bis-helicenes can either proceed to the full double annulation or be interrupted by addition of molecular oxygen at an intermediate stage. The regioselectivity of the interrupted cyclization cascade for bis-helicenes confirms that relief of antiaromaticity is a dominant force for these facile ring closures. Computational analysis reveals the unique role of the preexisting negatively charged cyclopentadienyl moiety in directing the 2nd negative charge at a specific remote location and, thus, creating a localized antiaromatic region. This region is the hot-spot that promotes the initial cyclization. Computational studies, including MO analysis, molecular electrostatic potential maps, and NICS(1.7)ZZ calculations evaluate the interplay of the various effects including charge delocalization, helicene strain release, and antiaromaticity. The role of antiaromaticity relief is further supported by efficient reductive closure of the less strained mono-helicenes where the relief of antiaromaticity promotes the cyclization even when the strain is substantially reduced. The latter finding significantly expands the scope of this reductive alternative to the Scholl ring closure.

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π‐Extended Helical Nanographenes: Synthesis and Photophysical Properties of Naphtho[1,2‐a]pyrenes**

Cited by 4 publications

References 60 publications

Synthesis and Properties of Achiral and Chiral Dipyrenoheteroles and Related Compounds

Synthesis and Properties of Achiral and Chiral Dipyrenoheteroles and Related Compounds

Localized Antiaromaticity Hotspot Drives Reductive Dehydrogenative Cyclizations in Bis- and Mono-Helicenes

Localized Antiaromaticity Hot-spot Drives Reductive Dehydrogenative Cyclizations in Bis- and Mono-Helicenes

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