Length-dependent symmetry in narrow chevronlike graphene nanoribbons

We report the structural and electronic properties of narrow chevron-like graphene nanoribbons (GNRs), which depending on their length are either mirror or inversion symmetric. Additionally, GNRs of different length can form molecular heterojunctions based on an unusual binding motif

Molecular Networks and Surface Engineering for Single Molecule Studies: From Spatial Separation to Emergent Properties

Functional molecules, among them artificial rotors, motors or gears, have been extensively studied over the past two decades with the aim to incorporate them into nanoscale devices, machines or factories. A plethora of studies have been conducted on functional molecules within a 3D (solution) environment while their investigation on atomically flat 2D surfaces despite being often a laborious effort has proven to add important insight. A less studied, but nevertheless important aspect is the (engineered) environment in which they operate, such as within the pore of a molecular network. Here, we review studies on the confinement of functional molecules within (porous) host–guest networks on atomically flat surfaces and discuss the effects this has on the operation of the functional molecule in question. To this end we will also provide a brief introduction to host–guest chemistry on surfaces. We will also present other methods to spatially arrange functional molecules, for instance through the use of specially engineered pre-patterned surfaces. Lastly, we will pay attention to the use of self-assembled networks to study emergent behavior of functional molecules

On‐Surface Ullmann‐Type Coupling: Reaction Intermediates and Organometallic Polymer Growth

Abstract Ullmann‐type coupling is the most widely used on‐surface reaction to form rationally designed bottom‐up molecular nanoarchitectures. A commonly observed reaction product in this reaction is an organometallic phase, however little is known about the formation of this phase. The on‐surface polymerization of the prochiral precursor 6,12‐dibromochrysene (DBCh) on Ag(111) is studied. Upon annealing of DBCh on Ag(111), a linear organometallic polymer forms. However, the delicate energy balance involved in the polymerization of DBCh is such that, at room temperature, several reaction intermediates, which eventually lead to the formation of the organometallic polymer, can be observed experimentally. Organometallic monomers, dimers, and trimers are finds, that self‐assemble into distinct networks. The experimental availability of these reaction intermediates provides key insights into the formation of the organometallic polymer. Comparing the chirality of the intermediates and the polymer sheds additional light on the reaction mechanism leading to the formation of the polymer. The main finding is that the organometallic polymer is not formed by a simple coupling of the reaction intermediates, but rather requires the breaking and re‐establishing of the C─Ag bonds. Additionally, a Br‐enhanced growth mode is observed, where the split‐off halogens align the polymers, which results in an increased polymer length

Length-dependent symmetry in narrow chevron-like graphene nanoribbons

We report the structural and electronic properties of narrow chevron-like graphene nanoribbons (GNRs), which depending on their length are either mirror or inversion symmetric. Additionally, GNRs of different length can form molecular heterojunctions based on an unusual binding motif