Multiple pyrazolyazoindole/indazoles scaffolds-based visible-light photoswitches with versatile controlled photophysical properties.

Abstract

Azoheteroarenes-based photoswitches with high bidirectional isomerization and long thermal half-life (t_1/2) have attracted widespread attention from researchers. The diversity of molecular scaffolds has a profound impact on photoswitching performance, herein, we incorporated dynamic connection sites and scaffold optimization to construct a series of pyrazolyazoindole/indazoles (PAIs)-based photoswitches with adjustable photoswitching properties and versatile photophysical properties upon the irradiation of special wavelength, among them 4Z-H can be switched between states "lock" and "unlock" by Cu²⁺ ion and EDTA. Thermal stability of series 3Z and 4Z was more stable than other PAIs photoswitches for their intramolecular forces, while the steric effect weakened the thermal stability of series 5D, these results clarified the relationship between the PAIs scaffolds and their photoswitching properties. More importantly, ionic photoswitches (4D-N⁺) synthesized by modification of quaternary ammonium salt fragment exhibited excellent reversible photoswitching properties in aqueous solution with alkaline condition and concentrated glutathione (GSH). The assembly of fluorescence group (triphenylamine) endowed the PAIs scaffolds with optically controlled fluorescence properties. This research elucidated the relationship of scaffold-modification-function of PAIs and would inevitably provide a reliable foundation for the development of intelligent organic materials with photoswitching systems.