Document Type : Original Article
Department of Organic Colorants, Institute for Color Science and Technology, Tehran, Iran
Department of Chemistry, University of Kansas, Lawrence, KS 66045, United States
Department of Advanced Materials Chemistry, Graduate School of Engineering, Yokohama National University, Yokohama, Japan
Department of Resin and Additives, Institute for Color Science and Technology, Tehran, Iran
Center of Excellence for Color Science and Technology, Institute for Color Science and Technology, Tehran, Iran
This paper examines the role of protonation on the photochromic reactions of multi-responsive phenyl amine diarylethene derivatives (PA-DAEs). Reversible protonation and deprotonation provide a secondary stimulus for controlling the properties of light-responsive PA-DAEs, including solubility and thermal stability. For this reason, the phenylamine substituted DAEs were synthesized using a novel and efficient microwave-assisted synthetic route. Steady-state spectroscopy results indicated that the photocyclization and photocycloreversion reactions were reversible at different pH values. Even though, the acidic condition caused red-shift of the visible light absorption bands and generated a new absorption band at near-IR to IR region in the closed-ring structure but made blue-shift in the absorption spectra of the open-ring isomers. Also, it was showed that the excess amount of proton locked back the photochromic reaction. Results also indicated that the protonated closed-ring isomers of PA-DAEs are hydrophilic, whereas the deprotonated forms and protonated open-ring forms are hydrophobic. In addition to photoswitching and solubility of PA-DAEs under irradiation at different light wavelengths, the thermal stability of P-type PA-DAEs was also monitored in the presence of trifluoroacetic acid at different temperatures as external stimuli.