# Influence of Protonation and Iron(II) Complexation on Magnetic Interactions in Spin‐Labeled Mechanically Interlocked Molecules

## TL;DR

This study explores how protonation and iron(II) complexation affect the magnetic properties of a mechanically interlocked molecule, showing that mechanical bonding can significantly alter electronic structure.

## Contribution

The study demonstrates how mechanical bonding and chemical modifications can tune magnetic interactions in interlocked radical systems.

## Key findings

- Protonation and Fe(II) complexation significantly alter the magnetic interactions in the [2]‐rotaxane and its biradicals.
- Mechanical bonding induces profound changes in the electronic structure and spin states of the interlocked molecules.
- The results suggest potential applications in molecular electronics and spintronics through tunable spin states.

## Abstract

This study reports the effects of protonation and Fe(II) complexation on the exchange coupling and magnetic properties of a [2]‐rotaxane and its corresponding free‐axle biradicals. The rotaxane features nitronyl‐nitroxide units as bulky stopper groups, a triazole‐pyridine‐triazole ligand as the axle component, and a bipyridine moiety within the macrocyclic ring. Our findings, obtained by Electron Paramagnetic Resonance spectroscopy in solution and magnetometry in solid state, demonstrate that rotaxanation and protonation induce profound changes in the magnetic interactions of the biradical both in its free form and as complexed with Fe(II). These results highlight the transformative impact of the mechanical bond on the electronic structure of interlocked radical systems.

The study investigates the influence of protonation and Fe(II) complexation on exchange coupling and magnetic properties in a [2]‐rotaxane and its free‐axle biradicals. Mechanical bonding markedly modifies magnetic interactions, highlighting its potential for enabling the design of interlocked molecules with tunable spin states for advanced applications in molecular electronics and spintronics.