Spiers Memorial Lecture.Carbon nanostructures by macromolecular design - from branched polyphenylenes to nanographenes and graphene nanoribbons.

Zijie Qiu,Klaus Müllen,Akimitsu Narita

doi:10.1039/d0fd00023j

Abstract

Nanographenes (NGs) and graphene nanoribbons (GNRs) are unique connectors between the domains of 1D-conjugated polymers and 2D-graphenes. They can be synthesized with high precision by oxidative flattening processes from dendritic or branched 3D-polyphenylene precursors. Their size, shape and edge type enable not only accurate control of classical (opto)electronic properties, but also access to unprecedented high-spin structures and exotic quantum states. NGs and GNRs serve as active components of devices such as field-effect transistors and as ideal objects for nanoscience. This field of research includes their synthesis after the deposition of suitable monomers on surfaces. An additional advantage of this novel concept is in situ monitoring of the reactions by scanning tunnelling microscopy and electronic characterization of the products by scanning tunnelling spectroscopy.

Highlights

The elucidation of the benzene structure and the discussion of the aromaticity concept are classic topics in organic chemistry.[1,2,3] Benzene is a fascinating species, as a model for spectroscopic and theoretical studies, and as a starting compound for chemical functionalization and the subsequent synthesis of natural products and as a versatile building block for conjugated psystems
The pioneering experiments of Jurgen Rabe and Paolo Samorı demonstrated the formation of an ordered monolayer by physisorption of alkyl-substituted HBC 14, visualizing single molecules with the scanning tunnelling microscopy (STM) tip immersed in the supernatant solution on the substrate (Fig. 2A and B).[76,77]
22 | Faraday Discuss., 2021, 227, 8–45. Does this synthetic protocol leading to graphene nanoribbons (GNRs) meet the strict requirements of conjugated polymer (CP) synthesis in terms of structural perfection, processability and scalability? The question regarding failure of the attening process cannot be set aside

Summary

Introduction

The elucidation of the benzene structure and the discussion of the aromaticity concept are classic topics in organic chemistry.[1,2,3] Benzene is a fascinating species, as a model for spectroscopic and theoretical studies, and as a starting compound for chemical functionalization and the subsequent synthesis of natural products and as a versatile building block for conjugated psystems. The resulting morphologies can be in uenced by the molecular structures and by the applied processing techniques, and the fabrication of thin- lm devices by unavoidable trial and error may lead to undesirable packing modes.[29,30] This uncertainty has strengthened the desire for electronic materials with either high intrinsic charge-carrier mobility or robust, controllable packing motifs. Such materials can potentially be realized with graphene and NG molecules. This text is a tribute to both the synthetic chemists from our group and the physicists from our partner groups

Solution synthesis

On-surface synthesis

Synthesis and opportunities in physics

Findings

Conclusion