A General Strategy Toward pH‐Resistant Phenolic Fluorophores for High‐Fidelity Sensing and Bioimaging Applications

Abstract

Aryl alcohol‐type or phenolic fluorophores offer diverse opportunities for developing bioimaging agents and fluorescence probes. Due to the inherently acidic hydroxyl functionality, phenolic fluorophores provide pH‐dependent emission signals. Therefore, except for developing pH probes, the pH‐dependent nature of phenolic fluorophores should be considered in bioimaging applications but has been neglected. Here we show that a simple structural remedy converts conventional phenolic fluorophores into pH‐resistant derivatives, which also offer “medium‐resistant” emission properties. The structural modification involves a single‐step introduction of a hydrogen‐bonding acceptor such as morpholine nearby the phenolic hydroxyl group, which also leads to emission bathochromic shift, increased Stokes shift, enhanced photo‐stability and stronger emission for several dyes. The strategy greatly expands the current fluorophores’ repertoire for reliable bioimaging applications, as demonstrated here with ratiometric imaging of cells and tissues.