Chiral Open-[60]Fullerene Ligands with Giant Dissymmetry Factors

Hashikawa, Yoshifumi; Okamoto, Shu; Sadai, Shumpei; Murata, Yasujiro

doi:10.1021/jacs.2c09556

Cited by 16 publications

(15 citation statements)

References 55 publications

(32 reference statements)

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“…At around the same time, Fuchter and co‐workers found that bis(methano)[60]fullerenes show a fast and high photocurrent response in CPL‐detecting devices [17] . Very recently, we reported a high dissymmetry factor of g abs =±0.20 at 710 nm for an open [60]fullerene [18] . Under these circumstances, we thus focused on the synthesis of donor–acceptor type chiral open [60]fullerenes targeted toward a broadband CD activity up to NIR region, in which the effective orbital hybridization with the donor units potentially renders low‐energy transitions electric dipole‐allowed [19, 20] .…”

Section: Introductionmentioning

confidence: 73%

“…Recently, we found that the reaction with nucleophiles such as phosphines results in the formation of zwitterionic open [60]fullerenes showing charge‐transfer transitions with considerably high oscillator strengths at the NIR region [21] . Herein, we used an acyclic diaminocarbene (:C(NMe 2 ) 2 ) as a nucleophile to obtain carbene adduct [22] 2 a while [60]fullerene substrate 1 a is a recently‐disclosed excellent chiral chromophore [18] (Figure 2a). In the presence of tetrakis(dimethylamino)ethylene (TDAE) as a carbene precursor, [23a] 1 a was therefore heated in o ‐dichlorobenzene (ODCB) at 180 °C for 15 min.…”

Section: Resultsmentioning

confidence: 99%

“…Reflecting the specific chirality along with the arrangement of functional groups on the orifice, 3 a should be optically active as in the case of 1 a. [18] Thus, its circular dichroism (CD), which is a measure of a difference in absorbance of right-and left-handed circularly polarized lights, is of particular interest. The optical resolution of racemic 3 a was done by the use of chiral HPLC, providing two enantiomers which are identifiable by the different retention times of 5.40 and 6.91 min for Fr.…”

Section: The Retro[2+2+2] Cycloaddition Causes the Ring-expansionmentioning

confidence: 99%

“…[17] Very recently, we reported a high dissymmetry factor of g abs = � 0.20 at 710 nm for an open [60]fullerene. [18] Under these circumstances, we thus focused on the synthesis of donor-acceptor type chiral open [60]fullerenes targeted toward a broadband CD activity up to NIR region, in which the effective orbital hybridization with the donor units potentially renders low-energy transitions electric dipole-allowed. [19,20] In this report, we showcase the synthesis and optical resolution of the first NIRabsorbing chiral open [60]fullerene as well as its remarkably high CD activity (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Near‐Infrared‐Absorbing Chiral Open [60]Fullerenes

et al. 2022

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Though [60]fullerene is an achiral molecular nanocarbon with I h symmetry, it could attain an inherent chirality depending upon a functionalization pattern. The conventional chiral induction of C 60 relies mainly upon a multiple addition affording a mixture of achiral and chiral isomers while their chiral function would be largely offset by the existence of pseudo-mirror plane(s). These are major obstacles to proceed further study on fullerene chirality and yet leave its understanding elusive. Herein, we showcase a carbene-mediated synthesis of C 1 -symmetric chiral open [60]fullerenes showing an intense far-red to near-infrared absorption. The large dissymmetry factor of j g abs j = 0.12 was achieved at λ = 820 nm for circular dichroism in benzonitrile. This is, in general, unachievable by other small chiral organic molecules, demonstrating the potential usage of open [60]fullerenes as novel types of chiral chromophores.

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Section: Introductionmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 99%

Section: The Retro[2+2+2] Cycloaddition Causes the Ring-expansionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Near‐Infrared‐Absorbing Chiral Open [60]Fullerenes

et al. 2022

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“…Second, as far as chiroptical properties of helical NGs are concerned, there is still large room for improvement. For instance, the g abs value of most chiral NGs stays in the range of 10 –3 , with limited examples approaching 10 –2 . − Considering that carbon materials such as chiral open-[60]fullerene with giant dissymmetry factors, up to 10 –1 , has been achieved, there is no reason to be satisfied with the state-of-the-art chiroptical properties that synthetic helical NGs have displayed.…”

Section: Summary and Outlookmentioning

confidence: 99%

Helical Synthetic Nanographenes with Atomic Precision

Zhu

Wang

2023

Acc. Chem. Res.

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Conspectus Understanding and harnessing the properties of nanoscale molecular entities are considered as new frontiers in basic chemistry. In this regard, synthetic nanographene with atomic precision has attracted much attention recently. For instance, taking advantage of the marvelous bonding capability of carbon, flat, curved, ribbon-type, or cone-shaped nanographenes have been prepared in highly controllable and elegant manner, allowing one to explore fascinating molecular architectures with intriguing optical, electrochemical, and magnetic characteristics. This stands in stark contrast to other carbon-rich nanomaterials, such as graphite oxides or carbon quantum dots, which preclude thorough investigations because of complicate structural defects. Undoubtedly, synthetic nanographene contributes strongly to modern aromatic chemistry and represents a vibrant field that may deliver transforming functional materials crucial for optoelectronics, nanotechnologies, and biomedicine. Nonetheless, in many cases, synthesis and characterization of nanographene compounds are highly demanding. Low solubility, high molecular strain, undesired selectivity, as well as incomplete or excessive C–C bond formation are common impediments, that require formidable efforts to control the molecular geometry, to modulate the edge structure, to achieve accurate doping, or to push the upper size boundary. These endeavors are indispensable for establishing structure–property relationships, and lay down foundation for exploring synthetic nanographenes at a high level of sophistications. In this Account, we summarize our contributions to this field by presenting a series of helical synthetic nanographenes, such as hexapole [7]helicene (H7H), nitrogen-doped H7H, hexapole [9]helicene (H9H), superhelicene, and supertwistacene. This kind of giant synthetic nanographene reaches the size domain of carbon quantum dots, albeit has precise atomic structure. It provides a unique platform to study aromatic chemistry and chirality at the nanoscale. We discuss synthetic methods and point out, in particular, the strengths and pitfalls of Scholl oxidation, which are expected to be valuable for making synthetic nanographenes in general. In addition, we illustrate their exciting electrochemical and photophysical performance, which include, but are not limited to, reversible multielectron redox chemistry, record high panchromatic absorption, impressive photothermal behavior, and extremely strong Cotton effect. These unusual characteristics are convincingly traced back to their three-dimensional conjugated architectures, highlighting the critical roles of π-electron delocalization, heteroatom-doping, substitution, and molecular symmetry in determining nanographenes’ properties and functions. Lastly, we put forward our understanding on the challenges and opportunities that lies ahead and hope this Account will inspire ever more ambitious achievements from this attractive area of research.

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A Double Twisted Nanographene with a Contorted Pyrene Core

Dong,

Zhang,

Hashikawa

et al. 2024

Angewandte Chemie

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The mature synthetic methodologies enable us to rationally design and produce chiral nanographenes (NGs), most of which consist of multiple helical motifs. However, inherent chirality originating from twisted geometry has just emerged to be employed in chiral NGs. Herein, we report a red‐emissive chiral NG constituted of orthogonally arranged two‐fold twisted π‐skeletons at a contorted pyrene core which contributes to optical transitions of S0 → S1 and vice versa. The thus‐obtained NG exhibited a robustness on its redox properties through 2e– uptake/release. The chemical oxidation generated stable radical cation whose absorption covers near‐infrared I and II regions. Overall, the contorted pyrene core governs electronic nature of the chiral NG. The twist operation on NGs would be, therefore, a design strategy to alter conventional chirality induction on NGs.

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Chiral Open-[60]Fullerene Ligands with Giant Dissymmetry Factors

Cited by 16 publications

References 55 publications

Near‐Infrared‐Absorbing Chiral Open [60]Fullerenes

Near‐Infrared‐Absorbing Chiral Open [60]Fullerenes

Helical Synthetic Nanographenes with Atomic Precision

A Double Twisted Nanographene with a Contorted Pyrene Core

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