Influence of Protonation on the Photochromic Behavior, Phase Transfer and Thermal Stability of Phenylamine-Substituted Diarylethenes

Document Type : Original Article


1 Department of Organic Colorants, Institute for Color Science and Technology, Tehran, Iran

2 Department of Chemistry, University of Kansas, Lawrence, KS 66045, United States

3 Department of Advanced Materials Chemistry, Graduate School of Engineering, Yokohama National University, Yokohama, Japan

4 Department of Resin and Additives, Institute for Color Science and Technology, Tehran, Iran

5 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.


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