Substituent effects on paratropicity and diatropicity in π-extended hexapyrrolohexaazacoronene

Takase, Masayoshi; Takata, Toshikazu; Oki, Kosuke; Mori, Shigeki; Uno, Hidemitsu

doi:10.1039/d2sc07037e

Cited by 2 publications

(1 citation statement)

References 46 publications

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“…This might be due to the rigidity of the polycondensed systems, wherein the antiaromaticity induces only slight distortion. [85] Since cycloheptatrienyl anions cannot be distorted to the extent to which COT is, their HOMO-LUMO gaps correspond to the absorption in the visible region. We used TD-DFT calculations to predict the absorption spectra of compounds 1-16 and compared them with the registered spectra of stable 11-12 and 14-15.…”

Section: Relationships Between the Criteriamentioning

confidence: 99%

Antiaromaticity of Cycloheptatrienyl Anions: Structure, Acidity, and Magnetic Properties

Salikov,

Belyy,

Ilyushchenko

et al. 2024

Chemistry A European J

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Investigations of the nature and degree of antiaromaticity of cycloheptatrienyl anion derivatives using both experimental and computational tools are presented. The ground state of cycloheptatrienyl anion in the gas phase is triplet, planar and Baird‐aromatic. In DMSO, it assumes a singlet distorted allylic form with a paratropic ring current. The other derivatives in both phases assume either allylic or diallylic conformations depending on the substituent pattern. A combination of experimental and computational methods was used to determine the pKa values of 16 derivatives in DMSO, which ranged from 36 to –10.7. We revealed that the stronger stabilization of the anionic system, which correlates with acidity, does not necessarily imply a lower degree of anti‐aromaticity in terms of magnetic properties. Conversely, the substitution pattern first affects the geometry of the ring through the bulkiness of the substituents and their better conjugation with a more distorted system. Consequently, the distortion reduces the cyclic conjugation in the π‐system and thereby decreases the paratropic current in a magnetic field, which manifests itself as a decrease in the NICS. The triplet‐state geometries and magnetic properties are nearly independent on the substitution pattern, which is typical for simple aromatic systems.

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Section: Relationships Between the Criteriamentioning

confidence: 99%

Antiaromaticity of Cycloheptatrienyl Anions: Structure, Acidity, and Magnetic Properties

Salikov,

Belyy,

Ilyushchenko

et al. 2024

Chemistry A European J

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Orbicular‐Donor–Acceptor System in N‐doped Nanographene for Highly Efficient NIR‐II Photothermal Therapy

Zhao,

Qu,

et al. 2024

Adv Healthcare Materials

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Developing stable and efficient photothermal agents (PTAs) for the second near‐infrared window (NIR‐II, 1 000–1700 nm) photothermal therapy (PTT) is highly desirable but remains challenging. Herein, a facile strategy to prepare NIR‐II nano‐PTA based on the ionic N‐doped nanographene hexapyrrolohexaazacoronene (HPHAC) is reported featuring a specific orbicular‐donor–acceptor (O‐D–A) structure. Oxidizing HPHAC 1 to dication 12+ causes a substantial decrease in its band gap, leading to a shift in absorption from the confined UV region to a broad absorption range that reaches up to 1400 nm. The dication 12+ exhibits global aromaticity and excellent stability. Theoretical investigation demonstrates that the strong NIR‐II absorption of 12+ is attributed to a distinct inner‐to‐outer intramolecular charge transfer. Encapsulating 12+ with amphiphilic polymers results in water‐soluble 12+ NPs with retained optical characteristics. The 12+ NPs exhibit exceptional biocompatibility, intense photoacoustic responses, and a high photothermal conversion efficiency of 72% under the 1064 nm laser irradiation, enabling efficient PTT of cancer cells. The “O‐D–A” system on HPHAC, which is created by a simple redox approach, provides a novel strategy to construct efficient NIR‐II photothermal materials through molecular engineering of nanographenes.

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Substituent effects on paratropicity and diatropicity in π-extended hexapyrrolohexaazacoronene

Abstract: Research into the application of antiaromatic compounds as molecular materials is an attractive strategy in the development of electronic materials. Antiaromatic compounds have traditionally been considered to be unstable, and...

Cited by 2 publications

References 46 publications

Antiaromaticity of Cycloheptatrienyl Anions: Structure, Acidity, and Magnetic Properties

Antiaromaticity of Cycloheptatrienyl Anions: Structure, Acidity, and Magnetic Properties

Orbicular‐Donor–Acceptor System in N‐doped Nanographene for Highly Efficient NIR‐II Photothermal Therapy

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