# Oxidation-Triggered Formation of Diradical Cations from Paramagnetic Molecules and Their Spin Density Evolution

## TL;DR

This paper explores how to control spin-polarized electron transport in molecules using redox stimuli to manipulate their magnetic properties.

## Contribution

The study introduces new paramagnetic molecules and demonstrates controlled formation of diradical cations with tunable spin density distributions.

## Key findings

- Four paramagnetic molecules were synthesized and converted into diradical cations through redox stimuli.
- Spin density distributions in diradical cations were controlled and confirmed using EPR and DFT.
- Intramolecular magnetic coupling was observed in the diradical cations.

## Abstract

Controllable intramolecular spin-polarized flow refers to the manipulation of spin-polarized electron transport within molecules through externally applied stimuli, thereby modulating their intramolecular spin characteristics and magnetic properties. In this work, we designed and synthesized four paramagnetic molecules, PDTN-NN, PDTN-IN, PO-NN, and PO-IN, by introducing nitronyl nitroxide (NN) and iminonitroxide (IN) radicals into phenothiazine and phenoxazine frameworks. Remarkably, we successfully generated the corresponding radical-substituted radical cations (diradical cations) and controlled their spin density distributions (SDDs) through redox stimuli. UV-Vis absorption spectroscopy, cyclic voltammetry (CV), electron paramagnetic resonance (EPR), and density functional theory (DFT) were employed to confirm the formation of diradical cations during the redox processes. Furthermore, EPR spectroscopy and DFT calculations were also employed to provide clear evidence of intramolecular magnetic coupling in the diradical cations.