Stimuli‐Responsive Color/Fluorescence Dual‐Switching Behaviors of 1,10‐Phenanthroline‐Based Viologen Derivatives with Halogen Anions

Abstract Recently, stimuli‐responsive color/fluorescence dual‐switchable materials have attracted great attention, whereas most of them respond to monostimulus. Therefore, it is essential to design two or multi‐stimuli‐responsive color/fluorescence dual‐switchable materials and develop their applications. Viologens, which respond to the electric potential, light irradiation, pH, and heat, are suitable for the construction of two‐ or multi‐stimuli‐responsive materials. Moreover, their easily modified chemical structure, tunable electronic properties, and excellent electrochemical characteristics can endow viologens with the desired color/fluorescence dual‐switching behaviors. Herein, novel electro‐ and photo‐stimuli responsive color/emission dual‐switchable viologen derivatives phen‐Vio[Cl⁻ I⁻], phen‐Vio[2Cl⁻] and phen‐Vio[2I⁻] employing fluorophore 1,10‐phenanthroline as an N‐aryl substituent and halogen ions as anions are designed and synthesized. The introduction of 1,10‐phenanthroline groups onto the viologen skeleton can endow viologen derivatives with the color/fluorescence dual‐switching properties under electrical or light stimulus. While the introduction of halogen ions allows viologen derivatives to respond to both electrical and light stimuli simultaneously. Multifunctional devices fabricated with phen‐Vio[Cl⁻ I⁻], phen‐Vio[2Cl⁻] or phen‐Vio[2I⁻] as active materials exhibit excellent electrochromic/electrofluorochromic and photochromic/photofluorochromic performance. Additionally, anti‐counterfeiting applications are successfully demonstrated by employing a commercial printer with self‐made ink and papers. It is believed that this work has important guiding significance for the design and development of multifunctional materials and devices.