Design and applications of multi-fluorophore metallacycles and metallacages

Integration of small organic fluorophores into supramolecular systems through coordination-driven self-assembly is gaining increasing interest in the areas of fluorescent materials, chemical sensors, and biomedical applications. Compared to systems modified with a single type of fluorophore, the introduction of two or more kinds of fluorophores can achieve multi-channel spectral changes in absorption and emission, enabling ratiometric detection and tunable light emission. Metal coordination not only allows precise control over the number and location of small organic fluorophores in supramolecular systems, but also enables integrating of small molecular fluorophores with specified light-absorbing and light-emitting properties, including single- or multi-step FRET, multi-channel ratio imaging, broader light-absorbing bands, and higher catalytic efficiency. This review focuses on constructing supramolecular assemblies through coordination-driven self-assembly with ligands modified by small organic fluorophores as core skeleton, and summaries recent progress in developing and applying these assemblies for artificial light-harvesting systems, biological applications, assembly kinetics study and cancer theranostics.