Insights into Extended Coupled Polymethines through the Investigation of Dual UV-to-NIR Acidochromic Switches Based on Heptamethine-Oxonol Dyes
Résumé
A series of heptamethine-oxonol dyes featuring different heterocyclic end groups were designed with the aim to explore structure-properties relationships in π-extend coupled polymethines. These dyes can be stabilised under three different protonation states, affording dicationic derivatives with an aromatic core, cationic heptamethines, and zwitterionic bis-cyanine forms. The variation of the end groups directly impacts the absorption and emission properties and mostly controls reaching either a colourless neutral dispirocyclic species or near-infrared zwitterions. The acidochromic switching between the three states involves profound electronic rearrangements leading to notable shifts of their optical properties that were investigated using a parallel experiment-theory approach, providing a comprehensive description of these unique systems.
