# A Molecular Machine Directs the Synthesis of a Rotaxane

## TL;DR

A light-driven molecular machine winds a strand around an axle to create a rotaxane, enabling new ways to build complex interlocked molecules.

## Contribution

A new machine-directed strategy for synthesizing rotaxanes through mechanical winding of molecular components.

## Key findings

- A molecular motor actively winds a strand around an axle to form a rotaxane.
- The approach creates thermodynamically disfavored crossings that are covalently captured.
- The method enables access to interlocked structures beyond traditional assembly techniques.

## Abstract

Preorganization by assembly or templating strategies is frequently used in the synthesis of rotaxanes. While these approaches have led to complex interlocked molecules, they are often limited by strict compositional requirements of templates and starting materials. Here, we use a molecular machine to direct the synthesis of a rotaxane by active shaping of starting materials through mechanical winding. Light induced rotation of a molecular motor actively winds a molecular strand around an axle, forming discrete, thermodynamically disfavored crossings between these two parts. Covalent capture preserves the kinetically stable entanglements, transforming the strand into a macrocycle that is subsequently released and mechanically trapped on the axle, yielding a rotaxane. Our machine‐directed strategy pioneers a new way of synthesizing rotaxanes by active mechanical shaping of molecular building blocks, enabling access to interlocked architectures beyond the reach of traditional assembly and templating approaches.

A light‐driven molecular machine winds a flexible strand around a rigid axle to synthesize a rotaxane. This machine‐directed approach enables access to molecular shapes previously unattainable by assembly or templating, demonstrating a generalizable strategy for expanding the chemical space of mechanically bonded molecules.