# Post-functionalization of triamino-phenazinium dyes to reach near-infrared emission

## TL;DR

This paper describes a method to modify a type of dye to emit light in the near-infrared range, which could be useful for biological imaging or treatment.

## Contribution

A one-step post-synthesis strategy to redshift the optical properties of triamino-phenazinium dyes by introducing electron-withdrawing groups.

## Key findings

- Phenazinium dyes were synthesized with absorption and emission in the red to near-infrared range.
- Electron-withdrawing groups were successfully introduced via acylation or aromatic nucleophilic substitution.
- One dye allowed further tuning of its properties through substitution with primary amines.

## Abstract

This study presents the synthesis and characterization of phenazinium dyes with absorption ranging from red to far-red, as well as emission extending into the far-red to near-infrared (NIR) region. The procedure involves the post-functionalization of a triamino-phenazinium that was recently reported as a theranostic agent. The introduction of electron-withdrawing moieties is accomplished through acylation or aromatic nucleophilic substitution. For one of the obtained products, a further substitution step could be achieved with primary amines to tune the electron density of the phenazinium core. The isolated dyes exhibit promising features that hold potential for future applications as biological markers or therapeutic agents.

We showed the possibility of redshifting the absorption and emission properties of triamino-phenazinium fluorophores by a one step post-synthesis strategy, involving the introduction of an electron-withdrawing group.