π‐Extended Diaza[7]helicenes by Hybridization of Naphthalene Diimides and Hexa‐<i>peri</i>‐hexabenzocoronenes

Dusold, Carolin; Sharapa, Dmitry I.; Hampel, Frank; Hirsch, Andreas

doi:10.1002/chem.202003402

Cited by 16 publications

(8 citation statements)

References 99 publications

(29 reference statements)

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“…Another research direction in helicene chemistry is the lateral extension of π-conjugated systems. − With more extensive conjugation, π-extended helicenes can be regarded as nanosolenoids and are predicted to possess intriguing electronic, magnetic, and spin properties. − In addition, their fascinating chiroptical features, such as circular dichroism (CD) and circularly polarized luminescence (CPL), have been intensively studied and are valuable for circularly polarized organic light-emitting diodes and bioimaging applications. − …”

Section: Introductionmentioning

confidence: 99%

Amplification of Dissymmetry Factors in π-Extended [7]- and [9]Helicenes

et al. 2021

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π-Extended helicenes constitute an important class of polycyclic aromatic hydrocarbons with intrinsic chirality. Herein, we report the syntheses of π-extended [7]helicene 4 and π-extended [9]helicene 6 through regioselective cyclodehydrogenation in high yields, where a “prefusion” strategy plays a key role in preventing undesirable aryl rearrangements. The unique helical structures are unambiguously confirmed by X-ray crystal structure analysis. Compared to the parent pristine [7]helicene and [9]helicene, these novel π-extended helicenes display significantly improved photophysical properties, with a quantum yield of 0.41 for 6 . After optical resolution by chiral high-performance liquid chromatography, the chiroptical properties of enantiomers 4 - P / M and 6 - P / M are investigated, revealing that the small variation in helical length from [7] to [9] can cause an approximately 10-fold increase in the dissymmetry factors. The circularly polarized luminescence brightness of 6 reaches 12.6 M –1 cm –1 as one of the highest among carbohelicenes.

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Section: Introductionmentioning

confidence: 99%

Amplification of Dissymmetry Factors in π-Extended [7]- and [9]Helicenes

et al. 2021

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“…For both the naphthalene‐ as well as the perylene‐derivatives, the two isomers can easily be separated by column chromatography and were fully characterized, revealing remarkable differences regarding their NMR and optical properties (see Supporting Information S1 for details). Clear assignment of the spectra to each isomer was possible by X‐ray analysis as previously reported [9] . The separation of the two isomers turned out to become the key step in this synthetic sequence.…”

Section: Resultsmentioning

confidence: 56%

“…In our previous study, we investigated such D–A systems in terms of their photophysical activity, with the HBC connected to the rylenediimide via the imide‐ N ‐position without any additional linker [8] . We recently expanded the concept and merged two naphthalenediimides (NDIs) to one HBC core through a benzimidazole‐bridge, generating a chiral superstructure with a di‐aza‐[7]helicene [9] . Our current approach is to fuse only one rylenediimide to the HBC core, but enlarge the library by utilizing not only NDIs but also PDIs as the second building block.…”

Section: Introductionmentioning

confidence: 99%

Helically and Linearly Fused Rylenediimide‐Hexabenzocoronenes

Dusold

Haines

Platzer

et al. 2021

Chemistry A European J

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Perylene‐ as well as naphthalenediimides were fused to hexabenzocoronenes (HBCs) at their imide position to realize highly π‐extended donor–acceptor (D–A)‐hybrids. Successful isomer separation in the first step was decisive to guarantee a straightforward synthetic sequence. Hexaphenylbenzenes as precursors were accessed via Diels–Alder reactions and reacted in a Scholl oxidation to yield the respective HBC derivatives. The fully conjugated benzimidazole linker, which separates the electron donating HBC from the electron accepting rylenediimide, enabled the formation of either a linear or a helical configuration. Largely different chemical, physical, and optoelectrical characteristics were noted for the two configurations. What stood out was their aggregation and their excited state deactivation depending on the solvent polarity. Results from global analysis of the femtosecond transient absorption data corroborated the formation of a charge‐transfer (CT) state that is stabilized in the helically fused configuration relative to the linear analogue. However, a comparison with spectroelectrochemical experiments failed to disclose evidence for a charge‐separated (CS) state.

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“…Similar to 30e , π-expanded N -hetero[7]helicene 31 (Figure ) has five-membered N -heterocycles fused to HBC. Hirsch and co-workers synthesized 31 in a yield of 43% by treating the corresponding precursor with FeCl 3 . Besides 31 , the other two possible constitutional isomers were formed only in minor quantities and could not be isolated into pure forms.…”

Section: Synthesis Of Curved Polycyclic Aromatics Through Scholl Reac...mentioning

confidence: 99%

The Scholl Reaction as a Powerful Tool for Synthesis of Curved Polycyclic Aromatics

2022

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The past decade has witnessed remarkable success in the synthesis of curved polycyclic aromatics through Scholl reactions which enable oxidative aryl–aryl coupling even in company with the introduction of significant steric strain. These curved polycyclic aromatics are not only unique objects of structural organic chemistry in relation to the nature of aromaticity but also play an important role in bottom-up approaches to precise synthesis of nanocarbons of unique topology. Moreover, they have received considerable attention in the fields of supramolecular chemistry and organic functional materials because of their interesting properties and promising applications. Despite the great success of Scholl reactions in synthesis of curved polycyclic aromatics, the outcome of a newly designed substrate in the Scholl reaction still cannot be predicted in a generic and precise manner largely due to limited understanding on the reaction mechanism and possible rearrangement processes. This review provides an overview of Scholl reactions with a focus on their applications in synthesis of curved polycyclic aromatics with interesting structures and properties and aims to shed light on the key factors that affect Scholl reactions in synthesizing sterically strained polycyclic aromatics.

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π‐Extended Diaza[7]helicenes by Hybridization of Naphthalene Diimides and Hexa‐peri‐hexabenzocoronenes

Cited by 16 publications

References 99 publications

Amplification of Dissymmetry Factors in π-Extended [7]- and [9]Helicenes

Amplification of Dissymmetry Factors in π-Extended [7]- and [9]Helicenes

Helically and Linearly Fused Rylenediimide‐Hexabenzocoronenes

The Scholl Reaction as a Powerful Tool for Synthesis of Curved Polycyclic Aromatics

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