# Tokyo University of Science and NITTC make interlocked nitrogen-doped carbon nanohoops in eight steps

- Published: 2026-11-12 05:19 UTC
- Section: Science › Chemistry
- Tags: catenane synthesis, cycloparaphenylene, nitrogen-doped nanohoop, gold-copper template, dynamic covalent bonds, co-conformational chirality, carbon nanotube segments, Tokyo University of Science
- URL: https://realtech.media/news/rt-ea7e102563b576ce6cdee7cf_tokyo_university_of/

**Japanese chemists combined reversible gold and copper bonds to assemble a [2]catenane of two strained rings in eight steps instead of more than 10, and biased its handedness with a chiral guest.**

![Tokyo University of Science and NITTC make interlocked nitrogen-doped carbon nanohoops in eight steps](https://realtech.media/media/2026/11/10e7b3d5dcc6e1de.jpg)
*U5780710, Wikimedia Commons, CC BY-SA 4.0*

A joint team from Tokyo University of Science (TUS) and the National Institute of Technology, Tokyo College (NITTC) has synthesized a [2]catenane of two nitrogen-doped cycloparaphenylene nanohoops in eight steps from commercially available starting materials, according to tus.ac.jp [1]. The work was published online in Angewandte Chemie International Edition and selected as a Hot Paper. The overall yield was 2.9% [1].

Catenanes are molecules in which rings are mechanically interlocked like chain links, with no chemical bonds between them. Cycloparaphenylenes (CPPs) are curved rings of para-linked benzene units and correspond to the shortest segments of carbon nanotubes. Such catenanes are hard to make: CPPs are highly strained, so the strain must be introduced only after the rings are interlocked [1].

## Two dynamic bonds in one pot

Conventional routes carry out separate stages: temporarily linking partial frameworks of the two rings, closing the rings, and forming the strained CPP framework. They typically take more than 10 steps, with overall yields from 0.02% to 4.3% [1].

The new route combines two kinds of bonds that break and re-form reversibly in solution. One is the gold(I)-carbon σ-bond in macrocyclic gold complexes, the basis of the gold-template method for CPP synthesis developed earlier by members of the team. The other is the copper(I)-nitrogen coordination bond, taken from Sauvage's classical copper-template approach [1].

The researchers added a copper(I) salt to a nitrogen-containing macrocyclic gold(I) complex and heated the mixture. The two bond types worked together to assemble an interlocked gold-copper complex in a single pot. Removing the metals gave a metal-free [2]catenane of two fully π-conjugated nitrogen-doped [12]CPP-based nanohoops [1]. From mass spectrometry and quantum chemical calculations, the authors proposed that copper(I) coordination acts as a template and drives the dynamic reorganization toward the catenane [1].

## Handedness controlled by a chiral guest

The catenane shows co-conformational chirality: depending on the relative orientation of its two rings, it can be right-handed or left-handed. After the researchers added the chiral aluminum complex CASA-Na, circular dichroism spectroscopy showed the molecule biased toward one handedness, depending on which enantiomer of the reagent was used [1].

A non-interlocked nanohoop showed almost no such effect, which the team took as confirmation that the chirality comes from the interlocked structure [1].

The team was led by Tomohito Ide (NITTC) and Yoshitaka Tsuchido (TUS), with collaborators from Kyoto University and TUS. Tsuchido said the approach could allow precise synthesis of topologically complex π-electron nanomaterials, and that guest-induced control of handedness may open routes to chiral materials with tunable optical and electronic properties [1].

## Sources

1. [tus.ac.jp](https://www.tus.ac.jp/en/mediarelations/archive/20261109_0109.html)
2. [Nanowerk](https://www.nanowerk.com/nanotechnology-news3/newsid=70586.php)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-ea7e102563b576ce6cdee7cf_tokyo_university_of/