BINOL-like atropisomeric chiral nanographene

Li, Shengtao; Li, Ranran; Zhang, Yi-Kang; Wang, Shutao; Ma, Bin; Zhang, Bin; An, Peng

doi:10.1039/d2sc06244e

Cited by 18 publications

(15 citation statements)

References 73 publications

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“…The CD response at 660 nm makes it potentially applicable in long-wavelength region photosensing. It is noted the axially chiral NGs with CD absorptions extending to 650 nm are unknown until now (see Figures S18 to S19). − The limited existing examples of the chiral NGs with CD responses above 650 nm are helical NGs with multiple helixes and expanded conjugation, which was difficult to synthesize via multiple (>5) steps (Figure S20). ,− This indicates that the arrangement of nonbenzenoid NGs in axial configuration via dimerization method is an efficient way to construct chiral materials, which may extend the CD response to the NIR region, in short synthetic steps.…”

Section: Resultsmentioning

confidence: 99%

“…Accompanying with the unique phenomenon of the sole existence of homoconfiguration dimers in the packing mode of 2 , which is also referred as to “self-sorting” character, 2 crystallizes in the I222 chiral space group, without inversion points and symmetry planes, containing one molecule in the asymmetric unit (Table S6). This character is totally different from other reported axial chiral benzenoid NGs − , and thus provides the potential applications in second-order nonlinear optics which will be discussed below.…”

Section: Resultsmentioning

confidence: 99%

“…For instance, An et al synthesized an oxa-doped hexa-peri-hexabenzocoronene (HBC) based chiral NG, exhibiting circularly polarized luminescence. 24 The axially chiral 5,5′-bibenzo[rst]pentaphene was also reported, demonstrating symmetry-breaking charge transfer. 25 Martı ́n and co-workers have recently reported a helically arranged molecular nanographene composed of two orthogonal dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene moieties covalently connected through a tetra-fluorobenzene ring, creating a chiral axis thorough the molecule (Scheme 1c).…”

Section: ■ Introductionmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Axially Chiral Nonbenzenoid Nanographene with Second Harmonic Generation Property

Qin,

Xie,

et al. 2024

J. Am. Chem. Soc.

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“…The incorporation of helical structures into planar nanographene can induce asymmetry, resulting in stereoisomerism and chiroptical properties [17][18][19][20][21] . The pyridinic nitrogen atoms located at the skeleton of nanographene can be protonated or can coordinate with protons or metal ions, owing to their lone electron pairs [22][23][24] .…”

Section: Introductionmentioning

confidence: 99%

“…The incorporation of helical structures into planar nanographene can induce asymmetry, resulting in stereoisomerism and chiroptical properties. [17][18][19][20][21] The pyridinic nitrogen atoms located at the skeleton of nanographene can be protonated or can coordinate with protons or metal ions, owing to their lone electron pairs. [22][23][24] Consequently, the coexistence of pyridinic nitrogen-doped atoms and helical structures within a molecule enables the modulation of their intrinsic electronic and optical properties and facilitates the manipulation of their chiroptical characteristics through mechanisms such as metal coordination or protonation.…”

Section: Introductionmentioning

confidence: 99%

Diazananographene with Quadruple [5]Helicene Units: Synthesis, Optical Properties, and Supramolecular Assembly

Ma,

Xing,

Chai

et al. 2024

Organic Materials

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A helical diazananographene (1) was synthesized using sterically hindered t-butyl groups to inhibit further dehydrocyclization of [5]helicene units. These t-butyl groups stabilized the conformation of [5]helicene units, thus resulting in three stable conformers of 1, comprising a pair of enantiomers (1-(P, P, P, P) and 1-(M, M, M, M)) and a mesomer (1-(P, P, M, M)). In comparison to its planar analogs, helical 1 exhibited broadened peaks in its absorption and emission spectra, with an increase in the emission quantum yield from 0.3 to 0.6. The significantly enhanced radiative decay rate (kr) accounted for the increase in the quantum yield of 1. It was found that 1 could be fully protonated upon the addition of an equivalent acid. Furthermore, 1 assembled into a chiral trimeric metallosupramolecular complex upon coordination with the PdII units. Both protonated 1 and the metallosupramolecular complex of 1 exhibited an enhanced circular dichroic response. These findings revealed that the incorporation of a helical structure and pyridinic nitrogen-doping into the nanographene can allow the synthesis of responsive chiroptical graphenic materials, which can serve as building blocks for chiral hierarchical metallosupramolecular structures.

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A Deep‐Red Emissive Sulfur‐Doped Double [7]Helicene Photosensitizer: Synthesis, Structure and Chiral Optical Properties

Yang,

Ren,

Feng

et al. 2024

Angewandte Chemie

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Doping of polycyclic conjugated hydrocarbons (PCHs) with sulfur atoms is becoming more and more important as a means of creating unique functional materials. Recently, thiophene‐containing multiple helicenes have garnered enormous attention due to their intriguing electronic and (chir)optical properties compared with carbohelicenes. However, the efficient synthesis of thiopyran‐containing multiple helicenes and the underlying sulfur doping mechanisms are rather unexplored. Herein, the synthesis and structural analysis of a thiopyran‐containing double [7]helicene 3 are reported. X‐ray crystallographic analysis reveals 3 and its dication with C2‐symmetric propeller‐shape structure and compact p‐p interaction in the solid state. 3 exhibits deep‐red to near‐infrared (NIR) fluorescence emission. Tunable aromaticity of the central benzene ring and thiopyran rings is found by chemical oxidation, which is further confirmed by nucleus‐independent chemical shift (NICS), anisotropy of the induced current density (AICD) and harmonic oscillator model of aromaticity (HOMA) analysis. Furthermore, the chiral and photosensitizing characters of 3 are investigated. The excellent deep‐red to NIR fluorescence, circularly polarized luminescence (CPL) and photosensitizing activities suggest that 3 can be used as an outstanding photosensitizer in photodynamic therapy (PDT) and bioimaging, especially paving the way for future CPL‐PDT and CPL‐bio‐probe applications.

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BINOL-like atropisomeric chiral nanographene

Abstract: Interest in making chiral polycyclic aromatic hydrocarbons (PAHs) or nanographenes (NGs) has greatly increased recently. To date, a majority of chiral nanocarbons have been designed based on helical chirality. Here,...

Cited by 18 publications

References 73 publications

Axially Chiral Nonbenzenoid Nanographene with Second Harmonic Generation Property

Axially Chiral Nonbenzenoid Nanographene with Second Harmonic Generation Property

Diazananographene with Quadruple [5]Helicene Units: Synthesis, Optical Properties, and Supramolecular Assembly

A Deep‐Red Emissive Sulfur‐Doped Double [7]Helicene Photosensitizer: Synthesis, Structure and Chiral Optical Properties

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