Advances in viologen-based stimulus-responsive crystalline hybrid materials

Abstract

Stimuli-responsive materials are a new class of smart materials that have received continuous scientific attention because they can exhibit rapid responses (with corresponding physical or chemical changes) under environmental stimuli. Among them, crystalline chromic hybrid materials that exhibit reversible color changes have become good candidates due to their variable structures as well as their highly designable and interesting properties under external stimuli such as light, heat, pressure, or electricity. A recent investigation found that viologens (4,4′-bipyridine derivatives) have been widely used for the construction of organic and inorganic hybrid chromic materials because of their good electron-deficient and redox properties. However, the development of multifunctional stimuli-responsive chromic materials remains a significant challenge. The purpose of this article is to propose design strategies for constructing viologen-based functionalized chromic materials that respond to physical, chemical, and multiple stimuli, reveal the structure–function relationship of crystalline chromic hybrids, and summarize the application potential of these chromic materials. This review will provide valuable assistance for researchers designing synthetic viologen-based chromic hybrid materials and facilitate new discoveries.