ABSTRACT
Herein, we describe water-soluble heteroaryl azopyridinium ionic photoswitches (HAPIPs). We aim to combine variations in five-membered heterocycles, their substitutions, N-alkyl groups at pyridinium nitrogen, the position of pyridinium center relative to azo group, counterions, and solvents, in achieving better photoswitching. Through these studies, we successfully tuned the half-life of Z isomers of the resultant HAPIPs between seconds to days in water. Extensive spectroscopic studies and density functional theory (DFT) computations unravelled the factors responsible for thermal relaxation behavior. Considering the versatility of these photoswitches, the tunability of half-lives and photoswitching in aqueous medium allows the scope of applications in several fields.
ABSTRACT
We report a new class of arylazopyrazolium-based ionic photoswitches (AAPIPs). These AAPIPs with different counter ions have been accessed through a modular synthetic approach in high yields. More importantly, the AAPIPs exhibit excellent reversible photoswitching and exceptional thermal stability in water. The effects of solvents, counter ions, substitutions, concentration, pH, and glutathione (GSH) have been evaluated using spectroscopic investigations. The results revealed that the bistability of studied AAPIPs is robust and near quantitative. The thermal half-life of Z isomers is extremely high in water (up to years), and it can be lowered electronically by the electron-withdrawing groups or highly basic pH.
ABSTRACT
A modular approach has been adopted to synthesize a wide range of visible light-driven photoswitchable azoheteroarenes. In this regard, we considered ortho substitution of cyclic amines in the aryl ring and varied substitution patterns. Using detailed spectroscopic studies, we established a relationship between structure and photoswitching ability and also half-lives of the Z-isomers. Through this, we envision tunable and bidirectional longer wavelength photoswitches.