π-Extended Helical Multilayer Nanographenes with Layer-Dependent Chiroptical Properties

Niu, Wenhui; Fu, Yubin; Qiu, Zhen-Lin; Schürmann, Christian J.; Obermann, Sebastian; Liu, Fupin; Popov, Alexey A.; Komber, Hartmut; Ma, Ji; Feng, Xinliang

doi:10.1021/jacs.3c09350

“…This shielding is also evident for the PP isomer of pED7H and is observed for the PP/PM isomer pair of oED7H. [10] The geometry of these screw-type PP isomers results in an enhanced shielding effect of the extended HBC π-ring systems on these protons compared to the PM isomers (Table S3, S4). This feature could be helpful for a quick identification of different helicities of helical NGs.…”

Section: Methodsmentioning

confidence: 71%

“…Herein, we demonstrate the successful synthesis of a series of π-extended helical NGs bearing double [7]helicenes (ED7Hs) where the two [7]helicene units are fused at meta-(mED7H) or para-position (pED7H) of the middle benzene ring, respectively, differing from the previously reported oED7H where helicenes are fused at the ortho-position (Figure 1d). [10] Their distinct geometry has been thoroughly characterized by single-crystal analysis, revealing the increased interlayer distances of mED7H and pED7H, compared to that of oED7H. Interestingly, mED7H and pED7H display bright luminescence with high Φ f above 40 %, larger than most of the reported π-extended helical NGs.…”

Section: Introductionmentioning

confidence: 94%

Enhancing Chiroptical Responses in Helical Nanographenes via Geometric Engineering of Double [7]Helicenes

Niu,

Fu,

Deng

et al. 2024

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Helical nanographenes with high quantum yields and strong chiroptical responses are pivotal for developing circularly polarized luminescence (CPL) materials. Here, we present the successful synthesis of novel π‐extended double [7]helicenes (ED7Hs) where two helicene units are fused at the meta‐ or para‐position of the middle benzene ring, respectively, as the structural isomers of the reported ortho‐fused ED7H. The structural geometry of these ED7Hs is clearly characterized by single‐crystal X‐ray analysis. Notably, this class of ED7Hs exhibits bright luminescence with high quantum yields exceeding 40%. Through geometric regulation of two embedded [7]helicene units from ortho‐, meta‐ to para‐position, these ED7Hs display exceptional amplification in chiroptical responses. This enhancement is evident in a remarkable approximate fivefold increase in the absorbance and luminescence dissymmetry factors (gabs and glum), respectively, along with a boosted CPL brightness up to 176 M‐1 cm‐1, surpassing the performance of most helicene‐based chiral NGs. Furthermore, DFT calculations elucidate that the geometric adjustment of two [7]helicene units allows the precise alignment of electric and magnetic transition dipole moments, leading to the observed enhancement of their chiroptical responses. This study offers an effective strategy for magnifying the CPL performance in chiral NGs, promoting their expanded application as CPL emitters.

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“…Dieser Abschirmeffekt ist auch bei pED7H-PP und den PP/PM Isomerenpaar von oED7H beobachtbar. [10] Die Geometrie dieser schraubenförmigen PP-Isomere führt zu einem verstärkten Abschirmeffekt der erweiterten HBC-π-Ringsysteme auf diese Protonen im Vergleich zu den PM-Isomeren (Tabelle S3, S4). Dieser Effekt könnte hilfreich für eine schnelle Identifizierung verschiedener Helizitäten von helikalen NGs sein.…”

Section: Ergebnisse Und Diskussionunclassified

“…176 M À 1 cm À 1 für mED7H und pED7H. Diese Werte sind im Vergleich zu oED7H deutlich erhöht und übertreffen die Mehrheit der bekannten helicenbasierten NGs (Abbildung 5h, Tabelle S11), [9][10][11] was ein vielversprechendes Potenzial für CPL-Anwendungen demonstriert.…”

Section: Ergebnisse Und Diskussionunclassified

“…Bei diesen stehen zwei [7]Helicen-Einheiten jeweils meta (mED7H) oder para (pED7H) zueinander am mittleren Benzenring, im Gegensatz zu dem bereits bekannten oED7H, bei dem die Helicene ortho am zentralen Ring stehen (Abbildung 1d). [10] Ihre einzigartige Geometrie wurde eingehend durch Röntgen-Einkristalldiffraktometrie charakterisiert, welche erhöhte Zwischenschichtabstände in mED7H und pED7H im Vergleich zu oED7H offenbarte. mED7H und pED7H zeigen eine helle Lumineszenz mit hohen Φ f von über 40 %, größer als bei den meisten der bekannten π-erweiterten helikalen NGs.…”

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Verstärkung von chiroptischen Eigenschaften in helikalen Nanographenen durch geometrische Anpassung von Doppel‐[7]Helicenen

Niu,

Fu,

Deng

et al. 2024

Angewandte Chemie

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Helical nanographenes with high quantum yields and strong chiroptical responses are pivotal for developing circularly polarized luminescence (CPL) materials. Here, we present the successful synthesis of novel π‐extended double [7]helicenes (ED7Hs) where two helicene units are fused at the meta‐ or para‐position of the middle benzene ring, respectively, as the structural isomers of the reported ortho‐fused ED7H. The structural geometry of these ED7Hs is clearly characterized by single‐crystal X‐ray analysis. Notably, this class of ED7Hs exhibits bright luminescence with high quantum yields exceeding 40%. Through geometric regulation of two embedded [7]helicene units from ortho‐, meta‐ to para‐position, these ED7Hs display exceptional amplification in chiroptical responses. This enhancement is evident in a remarkable approximate fivefold increase in the absorbance and luminescence dissymmetry factors (gabs and glum), respectively, along with a boosted CPL brightness up to 176 M‐1 cm‐1, surpassing the performance of most helicene‐based chiral NGs. Furthermore, DFT calculations elucidate that the geometric adjustment of two [7]helicene units allows the precise alignment of electric and magnetic transition dipole moments, leading to the observed enhancement of their chiroptical responses. This study offers an effective strategy for magnifying the CPL performance in chiral NGs, promoting their expanded application as CPL emitters.

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Noncovalent Assembly Strategy for Efficient Synthesis of Dual‐Atom Catalysts

Zhang,

Dai,

Guo

et al. 2024

Adv Funct Materials

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0

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Diatomic catalysts (DACs), as a frontier of research on atomically dispersed catalysts, have drawn great attention, especially in electrocatalysis. However, most of the current synthetic strategies for DACs suffer from poor efficiency and high cost. In this work, a novel noncovalent assembly strategy is reported for the efficient synthesis of DACs. By the aid of two kinds of noncovalent intermolecular force, the π–π stacking and Coulomb forces, a pair of metal complex ions with opposite electrical charges is spontaneously loaded onto the carbon substrate and transformed into diatomic sites via thermal treatment. This noncovalent assembly approach shows universal feasibility for a broad spectrum of DACs (Ir–Fe, Pt–Fe, Pt–Co, and Pt–Ni). To prove the practical utility, the as‐prepared PtFe‐DAC is deployed as oxygen reduction reaction catalyst, performing excellent activity with a half‐wave potential of 0.935 V (vs RHE) and a 2.3 times higher turnover frequency than that of the single‐atomic Fe‐SAC. In situ characterization and theoretical calculation indicate that the adjacent Pt sites could endow moderate activation of oxygen molecule on Fe sites by lowering the electron pairing energy as well as the modulation of the d‐band center and spin states of Fe centers propelling the desorption of the intermediates.

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π-Extended Helical Multilayer Nanographenes with Layer-Dependent Chiroptical Properties

Cited by 23 publications

References 40 publications

Enhancing Chiroptical Responses in Helical Nanographenes via Geometric Engineering of Double [7]Helicenes

Enhancing Chiroptical Responses in Helical Nanographenes via Geometric Engineering of Double [7]Helicenes

Verstärkung von chiroptischen Eigenschaften in helikalen Nanographenen durch geometrische Anpassung von Doppel‐[7]Helicenen

Noncovalent Assembly Strategy for Efficient Synthesis of Dual‐Atom Catalysts

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