This Feature Article will discuss the fabrication of light-harvesting systems based on water-soluble macrocycles, such as cyclodextrins (CD), pillararenes (PA), calixarenes (CA), cucurbiturils (CB), and other macrocycles.

A dimeric fluorescent macrocycle m‐TPE Di‐EtP5 (meso‐tetraphenylethylene dimeric ethoxypillar[5]arene) is synthesized based on the meso‐functionalized ethoxy pillar[5]arene. Through the connectivity of two pillar[5]arenes by CC double bond, the central tetraphenylethylene (TPE) moiety is simultaneously formed. The resultant bicyclic molecule not only retains the host–guest properties of pillararenes but also introduces the interesting aggregation‐induced emission properties inherent in the embedded TPE structure. Three dinitrile derivatives with various linkers are designed as guests (G1, G2, and G3) to form host–guest assemblies with m‐TPE Di‐EtP5. The morphological control and fluorescence properties of the assemblies are successfully realized. G1 with a shorter alkyl chain as the linker completely threads into the cavities of the host. G2, due to its longer chain length, forms a linear supramolecular polymer upon binding to m‐TPE Di‐EtP5. G3 differs from G2 by possessing a bulky phenyl group in the middle of the chain, which can be further assembled with m‐TPE Di‐EtP5 to form supramolecular layered polymer and precipitated out in solution, and can be efficiently applied to photocatalytic reactions.

Photosensitizers (PSs), featuring switchable properties to achieve tunable reactive oxygen species (ROS) generation, are highly desirable in photodynamic treatment and antibacterial applications. A supramolecular strategy combined with aggregation-induced emission (AIE) characteristics for synergistic design of an effective PS has emerged as a promising approach to reduce its side effects. Herein, we have constructed a ternary supramolecular PS based on a two-step Förster resonance energy transfer (FRET) process using an AIE-active pillar[5]arene host, a spiropyran derivative (SP-G) guest, and Nile blue (NiB) dye in aqueous media. The reversible isomerization process of SP-G endows this PS with the “on–off” switchability. Under UV light irradiation, the guest SP-G (non-emissive closed-form) can be converted to merocyanine MC-G (emissive open-form). And the in situ formed MC-G can function as the first energy acceptor and an efficient PS for ROS generation. Meanwhile, the introduction of NiB promotes a synergistic ROS-generation activity, leading to a two-step dynamic FRET process in response to UV and visible light irradiation. Moreover, this photoswitchable system with excellent controllable fluorescence performance and ROS-generation ability can be applied to inactivation of cancer cells and bacteria. The present work on the basis of a supramolecular strategy provides a proof-of-concept and new insight for the fabrication of smart PS materials.