Dehydrative π-extension to nanographenes with zig-zag edges

Abstract

Zig-zag nanographenes are promising candidates for the applications in organic electronics due to the electronic properties induced by their periphery. However, the synthetic access to these compounds remains virtually unexplored. There is a lack in efficient and mild strategies origins in the reduced stability, increased reactivity, and low solubility of these compounds. Herein we report a facile access to pristine zig-zag nanographenes, utilizing an acid-promoted intramolecular reductive cyclization of arylaldehydes, and demonstrate a three-step route to nanographenes constituted of angularly fused tetracenes or pentacenes. The mild conditions are scalable to gram quantities and give insoluble nanostructures in close to quantitative yields. The strategy allows the synthesis of elusive low bandgap nanographenes, with values as low as 1.62 eV. Compared to their linear homologues, the structures have an increased stability in the solid-state, even though computational analyses show distinct diradical character. The structures were confirmed by X–ray diffraction or scanning tunneling microscopy.

Towards Nonalternant Nanographenes through Self‐Promoted Intramolecular Indenoannulation Cascade by C−F Bond Activation

“…Among various PAHs non‐alternant systems containing pentagons attract special interest, which stems from their unusual physical properties including high electron affinities and anomalous fluorescence . Until recently the synthetic chemists were mainly concentrated on the synthesis of alternant NGs, resembling the honeycomb fragment that is, composed exclusively of six‐membered rings . Meanwhile, the methods allowing the incorporation of pentagons into the large PAH structure still remain rather scarce…”

“…[3] Until recently the synthetic chemists were mainly concentrated on the synthesis of alternant NGs, resembling the honeycombf ragment that is, composed exclusively of six-membered rings. [4][5][6][7][8] Meanwhile, the methods allowing the incorporation of pentagons into the large PAH structures till remain rather scarce. [9À11] The synthetic difficulties related to pentagons-bearing structures are mainly associated with the enhanced strain caused by distortion of a p -system and deviationo fv alence angles from the optimal sp 2 -hybridized carbon atoms geometry.N aturally,t hese obstacles tend to exacerbate the synthetic accessibility of PAHs' cores containing severalp entagons even further.N evertheless,p hysical and chemicalp roperties acquired along with pentagons within the aromatic core justify the efforts to develop decent synthetic approaches towards such attractive structures.…”

Excellent Semiconductors Based on Tetracenotetracene and Pentacenopentacene: From Stable Closed-Shell to Singlet Open-Shell

“…The TT-dione 4 and the PPdione 5 were obtained in excellent yield via a double intramolecular acylations using TfOH as activator. 18 Addition of the lithium (triisopropylsilyl)acetylide to either 4 and 5 followed by SnCl 2 mediated reduction of the diol intermediates afforded the desired TT as dark blue solid and PP as dark green solid with yield around 50%. The structure of TT was confirmed by X-ray diffraction and the purity of samples was checked by 1 H NMR, MALDI-TOF measurement in which only one peak assigned to molecular ion of the materials was observed and by elemental analysis for PP (see Supporting information).…”

The True Amphipathic Nature of Graphene Flakes: A Versatile 2D Stabilizer

“…We firstly used DFT to rigorously determine the interaction energy ( E int ) between graphene flakes, water and decane. Since the properties of nanocarbons vary significantly with the their size, shape and edge topology [ 19 ] and graphene flakes possess two electrochemically distinctive regions: the basal plane surface, composed of conjugated sp 2 carbon atoms, and the edges, containing carbon atoms with dangling bonds, [ 20 ] we have considered both solvent molecules positioned above the surface and next to the edge of ten different graphene flakes. DFT calculations of eight graphene flakes (Γ 1 –Γ 8 ) with lateral dimensions in the range of 1–2 nm but different shapes and edges ( Figure A) show that the interactions between oil and flake surface are stronger ( E int is more negative) than between the oil and flake edges, regardless of the shape of flake or type of edge.…”