# Redox-Switchable Chalcogen Bonding for Anion Recognition and Sensing

## TL;DR

This paper introduces a new way to control chalcogen bonding using redox reactions, enabling sensitive anion sensing and molecular switches.

## Contribution

The first demonstration of redox-switchable chalcogen bonding for reversible anion recognition and sensing.

## Key findings

- Redox control modulates chalcogen bonding strength by up to three orders of magnitude.
- Chalcogen-bond-based sensors outperform similar halogen and hydrogen bond sensors in electrochemical responses.
- Redox-switchable anion recognition is demonstrated in aqueous-organic solvent systems.

## Abstract

Inspired by the success
of its related sigma-hole congener halogen
bonding (XB), chalcogen bonding (ChB) is emerging as a powerful noncovalent
interaction with a plethora of applications in supramolecular chemistry
and beyond. Despite its increasing importance, the judicious modulation
of ChB donor strength remains a formidable challenge. Herein, we present,
for the first time, the reversible and large-scale modulation of ChB
potency by electrochemical redox control. This is exemplified by both
the switching-ON of anion recognition via ChB oxidative activation
of a novel bis(ferrocenyltellurotriazole) anion host and switching-OFF
reductive ChB deactivation of anion binding potency with a telluroviologen
receptor. The direct linking of the redox-active center and ChB receptor
donor sites enables strong coupling, which is reflected by up to a
remarkable 3 orders of magnitude modulation of anion binding strength.
This is demonstrated through large voltammetric perturbations of the
respective receptor ferrocene and viologen redox couples, enabling,
for the first time, ChB-mediated electrochemical anion sensing. The
sensors not only display significant anion-binding-induced electrochemical
responses in competitive aqueous-organic solvent systems but can compete
with, or even outperform similar, highly potent XB and HB sensors.
These observations serve to highlight a unique (redox) tunability
of ChB and pave the way for further exploration of the reversible
(redox) modulation of ChB in a wide range of applications, including
anion sensors as well as molecular switches and machines.