# Single-Molecule Conductance through Hybrid Radially and Linearly π‑Conjugated Macromolecules Reveals an Unusual Intramolecular π‑Interaction

## TL;DR

This paper studies how combining radial and linear π-conjugated structures in molecules affects their electrical conductance at the single-molecule level.

## Contribution

The study is the first to examine molecules with both radial and linear π-conjugation in a single-molecule junction.

## Key findings

- Radial CPP components reduce conductance compared to linear phenyl substituents.
- Intramolecular van der Waals interactions between CPP rings and the backbone alter dihedral angles and π-orbital overlap.

## Abstract

We describe the design, synthesis, and single-molecule
junction
conductance of π-electron molecules bearing both radial and
linear π-conjugation pathways, whereby cycloparaphenylene (CPP)
radial cores are π-extended linearly with aryl alkyne substituents
as models for previously reported CPP-arylene ethynylene conjugated
polymers. Although radially and linearly conjugated molecules have
been studied previously in isolation as junction-bridging molecular
electronic units, this is the first study to examine molecules where
both topologies are operative. Our results reveal that the presence
of radial CPP components within the junction-spanning pathway leads
to a reduction in the conductance of the backbone compared to model
linear phenyl substituents. Through tight-binding and DFT-based calculations,
we attribute this conductance change to intramolecular van der Waals
(vdW) interactions between the CPP ring and the junction-spanning
arylene-ethynylene molecular backbone. These interactions induce changes
in the dihedral angles of the backbone, leading to a reduced overlap
of π orbitals within the molecular junction.