# Shifting Merocyanine-Imine Exchange with Visible Light

## TL;DR

This paper shows how visible light can control a chemical reaction between merocyanines and imines, enabling reversible material properties.

## Contribution

A new light-responsive dynamic covalent system using merocyanine and imine exchange is introduced.

## Key findings

- Visible light shifts the equilibrium between merocyanines and imines.
- The system can be repeatedly switched between dynamic and static states.
- This offers control over material properties in space and time.

## Abstract

We
show the dynamic covalent exchange between merocyanines
and
imines and demonstrate how the equilibrium composition can be shifted
with visible light. For this purpose, we exploited a negative photochromic
T-type merocyanine that engages in a covalent exchange with an aniline
nucleophile to provide an imine. Since the merocyanine can quantitatively
be converted into its spiropyran isomer that is nonreactive in the
exchange, the system can be shifted and trapped in the static spiropyran
state. In the dark, however, the system thermally reverts back to
the dynamic merocyanine that re-engages in the exchange. The process
of shifting/trapping and re-equilibration can be repeated multiple
times. The system provides opportunities for designing materials that
allow for spatial and temporal control over their dynamic properties.