# Synthesis and Properties of [3]Rotaxanes with Two Oligo(para‐phenylene) Axles

## TL;DR

Researchers synthesized [3]rotaxanes with oligo(para-phenylene) axles and studied their properties, including aggregation behavior and spectroscopic characteristics.

## Contribution

The novel synthesis of [3]rotaxanes with two oligo(para-phenylene) axles using a larger macrocyclic Ni complex and their controlled aggregation behavior.

## Key findings

- [3]rotaxanes with two oligo(para-phenylene) axles were synthesized in good yields using a larger macrocycle.
- The aggregation of octa(para-phenylene) derivatives was suppressed by the presence of the macrocycle in the rotaxanes.
- Photophysical studies showed that aggregation influences the properties of oligo(para-phenylene) structures.

## Abstract

Oligo(para‐phenylene) (PPn) is a π‐conjugated compound where phenylene units are directly connected at the 1,4‐positions. Utilizing the catalytic activity of the macrocyclic dihydrodibenzophenanthroline‐Ni complex, we succeeded in the synthesis of [3]‐ and [2]rotaxanes with PPn axles by biaryl coupling. The size of the macrocycle was critical to synthesize [3]rotaxanes, which consist of two oligo(para‐phenylene) axles, in good yields. The relationship between the length of the PPn structure on the 1H NMR spectra of the rotaxanes was studied. The aggregation of a PP8 derivative was suppressed by the presence of the macrocycle in the rotaxanes. A [3]rotaxane could be considered as a model compound of an aggregated PPn, and the photophysical studies disclosed the influence of the aggregation on the properties of PPn.

[3]‐ and [2]rotaxanes with oligo(para‐phenylene) axles were synthesized by Ni‐mediated biaryl coupling. [3]Rotaxanes were synthesized in good yields when a larger macrocyclic Ni complex was employed. The spectroscopic properties and the aggregation behavior of octa(para‐phenylene) derivatives were examined. The aggregated/non‐aggregated state could be controlled by utilizing the interlocked structure.