Pyrrole-Embedded Linear and Helical Graphene Nanoribbons

Abstract

Linear and helical graphene nanoribbons (L-PyGNR and H-PyGNR) bearing electron-rich pyrrole units have been synthesized by using the photochemical cyclodehydrochlorination (CDHC) reaction. The pyrrole units in the polymer backbone make the polymer electron-rich with moderate bandgap values and relatively high HOMO energy levels. The planarization of the pyrrole unit through cyclization yields a bandgap value almost 0.5 eV lower than that measured for polypyrrole. Conductivity values in the thin film up to 0.12 S/cm were measured for the chemically oxidized L-PyGNR (four-point method). Both GNRs showed excellent fluorescence sensing properties for TNT in solution with K SV values up to 6.4 × 10 6 M −1 .

A Series of Soluble Thieno-Fused Coronene Nanoribbons of Precise Lengths

“…Graphene nanoribbons (GNRs), which are commonly defined as quasi-one-dimensional (quasi-1D) cutouts of graphene with 1–100 nm widths and length/width ratios >10, − are a fascinating class of materials, bearing a great potential for organic electronics applications. − Their optical and electronic properties strongly depend on their structures, such as widths, lengths, shapes, and edges. − Besides control over the above-mentioned structural parameters, properties can be fine-tuned by incorporation of heteroatoms into the conjugated nanoribbon backbones. − In this context, the importance of organic synthesis is emphasized as a powerful tool to obtain structurally precise molecular ribbons/oligomers as fragments of GNRs and hence adjust the optoelectronic properties, in order to establish reliable structure–property relationships for 1D-extended π-systems. ,, …”

Nanographenes and Graphene Nanoribbons as Multitalents of Present and Future Materials Science

“…The helicene-like GNRs 61 and 62 synthesized by the photochemical cyclodehydrochlorination of the chlorinated polyphenylene precursors provide promising examples of chiral GNRs with single-handedness (Figure ). , Unfortunately, the helicity is created during the cyclodehydrochlorination without chiral selectivity, meaning that the obtained GNRs are still racemic mixtures. There is, thus, plenty of room to adopt state-of-the-art asymmetric syntheses to fully unleash the potential of chiral GNRs…”

“…Quite different ways of approaching GNRs are possible since they can be regarded either as (1) polyphenylenes extended laterally, (2) large PAHs grown into 1D, or (3) cut-outs from a graphene lattice . Indeed, various subunits have been carved out of graphene flakes by electron-beam lithography, while GNRs have been produced by slicing or squashing CNTs. − The structural versatility of GNRs is outstanding considering not only variations of their length, width, and edge structure, − but also heteroatom incorporation, − nonplanarity, and helicity, − as well as “drilling” of holes. − …”

The Changing Face of Research: The Use of Chemical Information Skills to Identify Novel Research Areas

“…An assignment like this could also help students explore the relationship between structure and properties. A recent article 27 introduces pyrrole-embedded graphene nanoribbons. This assignment could be used to encourage students to examine and speculate on differences in properties between the materials that would arise if the pyrrole was replaced with a slightly different heterocycle, such as a pyridine, triazine, or oxazole.…”