Anomalous Interfacial Electronic Structure of Solid Films of Non‐Planar π‐Conjugated Molecule 6‐Cycloparaphenylene

Abstract

n‐Cycloparaphenylene ([n]CPP) is a non‐planar π‐conjugated molecule with a macrocyclic, hoop‐like molecular structure that allows for control of the electronic structure unlike planar molecules. Thus, [n]CPP has the potential as a novel functional material in organic electronics. In this study, the unique electronic structure of [6]CPP is revealed, which originates from its macrocyclic molecular structure by comparison with p‐sexiphenyl, a linear molecule also consisting of six phenylenes. The morphology of the vapor‐deposited [6]CPP polycrystalline film is found to be highly dependent on the evaporation rate and the type of substrate. It is also found that a [6]CPP molecular layer is formed at the interface between the film and gold substrate, which has a much smaller energy gap than that of the bulk [6]CPP. This anomalous molecular layer is composed of [6]CPP molecules with a smaller dihedral angle than that in the bulk because of the interaction with a gold substrate. When [6]CPP is used as a semiconducting layer in electronic devices, this layer can play a role in improving the charge injection efficiency from the electrode to the [6]CPP film.

Conjugated Nanohoop Polymers based on Antiaromatic Dibenzopentalenes for Charge Storage in Organic Batteries

“…Conjugated nanohoops are considered promising candidates for electronics applications due to their extended π‐system, stiff structure and cyclic conjugation, but are little explored to date [2] . On a few occasions the charge transport properties of [ n ]CPPs were studied [14–16] . Nanohoops might be interesting materials for charge storage due to their rigid structure, intrinsic porosity and tunable properties.…”

“…[2] On a few occasions the charge transport properties of [n]CPPs were studied. [14][15][16] Nanohoops might be interesting materials for charge storage due to their rigid structure, intrinsic porosity and tunable properties. However, in only one case was the application of a CPP derivative investigated for charge storage.…”

“…Since several synthetic strategies have been established in the past 15 years that allow constructing these strained π‐systems, [7,8] it has now become feasible to explore applications of conjugated nanohoops. Examples have been reported where they are used as fluorescent biomarkers [9–12] as well as in optical devices as small molecules [13–16] . For many applications, properties inherent to polymers are desirable, such as processability, non‐crystallinity and solubility.…”

“…Examples have been reported where they are used as fluorescent biomarkers [9][10][11][12] as well as in optical devices as small molecules. [13][14][15][16] For many applications, properties inherent to polymers are desirable, such as processability, non-crystallinity and solubility. In order to fully explore the potential of conjugated nanohoops as organic materials, their incorporation into polymeric structures is of high relevance.…”

Methylene-Bridged [6]-, [8]-, and [10]Cycloparaphenylenes: Size-Dependent Properties and Paratropic Belt Currents

“…The production of cyclic molecular nanocarbons such as carbon nanorings (CNRs) and carbon nanobelts (CNBs) is an emerging topic in chemistry (Figure a) . Their unparalleled properties derived from their high symmetry and highly strained cyclic structure are innovative in the chemistry of aromatic molecules, leading to their unique applications . [ n ]­Cycloparaphenylene ([ n ]­CPP), where n benzene rings are connected in their para -positions, is the first and iconic CNR that dominated the chemistry of cyclic molecular nanocarbons in the past decade .…”