A Deep‐Red Emissive Cage‐in‐Rings Complex for Lysosome Imaging

ABSTRACT Bioimaging technology is a fundamental platform for visualizing biological processes and guiding clinical interventions. Consequently, developing effective strategies for constructing biocompatible, long‐wavelength emissive, and intrinsically selective bioprobes has long been a central goal in chemistry. Herein, we develop a stepwise assembly protocol to construct an exotic cage‐in‐rings bioimaging probe, TPBCage 6+ ⊂3CB[8] , through noncovalent association of a hexacationic cage (TPBCage 6+ ) with cucurbit[8]uril (CB[8]). The complex adopts a thermodynamically favored C 2 ‐symmetrical conformation rather than the expected C 3 ‐symmetrical analogue. It preserves two exposed pyridinium units, providing a structural basis for efficient cellular uptake, while the other four pyridinium units are partially shielded by CB[8], reducing nonspecific interactions in bioimaging to some extent compared with the free cage. Encapsulation by CB[8] effectively suppresses π–π stacking of the cage, improving its aqueous solubility. Concomitantly, CB[8] encapsulation narrows the energy gap of the cage, resulting in a red shift in emission from 552 to 652 nm and an enhanced fluorescence quantum yield. Benefiting from enhanced water solubility, good biocompatibility, and deep‐red emission, the complex enables lysosome‐selective imaging in deep‐red region. This work establishes an alternative supramolecular strategy for subcellular‐selective imaging, in which cage‐in‐rings confinement enables control over excited‐state properties, enabling the development of intrinsically selective bioimaging probes.