Bottom‐Up Synthesis of Necklace‐Like Graphene Nanoribbons

Abstract

Graphene nanoribbons (GNRs) with an unprecedented "necklace-like" structure were synthesized through a bottom-up chemical approach, based on the oxidative cyclodehydrogenation of tailor-made polyphenylene precursors. A polycyclic aromatic hydrocarbon consisting of 84 sp(2) carbons (C84) was also synthesized and characterized as a model compound. Characterizations by a combination of MALDI-TOF MS and FTIR, Raman, and UV/Vis absorption spectroscopy validated the formation of the necklace-like GNRs. The absorption spectrum and DFT calculations revealed a bandgap of approximately 1.4 eV for this novel GNR system, which has not been attained with other GNR structures, enabling further fine-tuning of GNR bandgaps by structural modulation.

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…[157] Thep oly-para-phenylene scaffold of the precursor for nanoribbon 164 was constructed by Suzuki polymerization. [158] After treatment with FeCl 3 ,t he necklace-like nanoribbon 164 was obtained in high yield.…”

“…Their syntheses have been extensively reviewed recently . Figure presents the structures of the two exemplary carbon nanoribbons 163 and 164 obtained in excellent yields by Feng, Müllen, and co‐workers from the corresponding polymeric precursors using FeCl 3 as an oxidant in a CH 2 Cl 2 /CH 3 NO 2 mixture. The precursor for nanoribbon 163 was obtained by Diels–Alder polymerization of an appropriate acetylene‐functionalized tetraarylcyclopentadienone monomer.…”

“…FeCl 3 ‐promoted planarization of the polymer furnished the nanoribbon with a cove‐type edge structure and width of 0.7–1.1 nm . The poly‐ para ‐phenylene scaffold of the precursor for nanoribbon 164 was constructed by Suzuki polymerization . After treatment with FeCl 3 , the necklace‐like nanoribbon 164 was obtained in high yield.…”

“…Their syntheses have been extensively reviewed recently. [5,155,156] Figure 11 presents the structures of the two exemplary carbon nanoribbons 163 [157] and 164 [158] obtained in excellent yields by Feng, Müllen, and co-workers from the corresponding polymeric precursors using FeCl 3 as an oxidant in aC H 2 Cl 2 /CH 3 NO 2 mixture.T he precursor for nanoribbon 163 was obtained by Diels-Alder polymerization [159] of an appropriate acetylene-functionalized tetraarylcyclopentadienone monomer.T he weight-average molecular weight (M w ) of the resulting polymer reached 640 kg mol À1 .F eCl 3 -promoted planarization of the polymer furnished the nanoribbon with ac ove-type edge structure and width of 0.7-1.1 nm. [157] Thep oly-para-phenylene scaffold of the precursor for nanoribbon 164 was constructed by Suzuki polymerization.…”

Emerging Bottom‐Up Strategies for the Synthesis of Graphene Nanoribbons and Related Structures

“…Thep ioneering work of Müllen and his group,b ased on the preparation of soluble polyphenylene precursors followed by aromatization using the cyclodehydrogenation (Scholl) reaction, set the tone in this area of research. [27][28][29][30][31][32][33][34][35][36] Using this strategy,s everal examples of GNRs with different sizes,shapes and edge topologies have been prepared and thoroughly characterized, especially in regard to their electronic properties.A lthough the Scholl reaction is still the method of choice to prepare well-defined GNRs,o ther research groups have been interested in developing alternative methods to further expand the diversity of GNR structures that could be prepared.…”