# Light-Induced Rotation of a Molecular Motor in the Confined Space of a Metal–Organic Nanocage

## TL;DR

Scientists created a molecular motor that can rotate fully inside a metal-organic nanocage when exposed to light and heat.

## Contribution

The first molecular motor-nanocage system enabling a full 360° rotation within a confined space.

## Key findings

- A stable host-guest complex was formed using noncovalent interactions between the motor and the nanocage.
- The motor's rotation occurs without being released from the nanocage despite significant geometric changes.
- This system does not rely on size-induced fit, a common mechanism in other inclusion complexes.

## Abstract

Molecular motors have been operated in a myriad of environments
since their inception more than two decades ago. Of particular interest
are systems in which a structural frame of reference for the motor’s
rotary motion is established. Examples include motors adsorbed on
surfaces, embedded in framework materials, used as dopants in liquid
crystals, or incorporated into polymer matrices. Embedding the molecular
motor as a guest in a supramolecular cage assembly, however, remains
an unexplored strategy. Such systems are particularly attractive,
as they would allow the motor’s rotation to drive mechanical
motion from within the assembly, provided the motion does not lead
to the guest motor’s release. Here, the first motor–nanocage
host–guest system in which a thermal and light-driven full
360° unidirectional rotational cycle occurs within the confined
space of the nanocage is reported. We identified key structural elements
that enable the formation of a host–molecular motor complex
with unprecedented stability, governed by a noncovalent interaction
between the motor’s alkyl–COOH moiety and a carbonyl
residue on the cage. This strategy allows the formation of stable
host–guest complexes without relying on a size-induced fit,
as is commonly observed in other inclusion complexes. This enables
rotation to occur within the cage cavity despite dramatic geometric
changes. We envision this strategy as a valuable tool for developing
a new generation of molecular motors operating in confined spaces.