Dynamically assembled photochromic cages operational in water with visible light.

Producing chemical nanostructures that can mimic the efficient adaptability of complicated biological systems to environment changes is among the main goals of nanotechnology. Progress in this area requires understanding of the adaptation mechanisms towards external stimuli at the molecular level. Due to rapid and precise spatiotemporal addressability, light-driven dynamic systems are particularly attractive for such mechanistic studies. Here, we show efficient formation of dynamic covalent cages that undergo a series of reversible constitutional changes driven by visible light. Their complex, yet predictable and often quantitative response to irradiation and other external stimuli (metal ions, pH) reveals design principles that can be applied to assemble adaptable molecular machines showing life-like behavior. Upon reduction of the dynamic imine bonds, stable covalent cages are isolated. Their response to red light, also in aqueous media, indicates the potential for in vivo applicability, as red light can deeply penetrate human tissues.