Supramolecular light-harvesting systems based on cucurbit[n]urils: SS-FRET and TS-FRET mechanisms and functional applications

Supramolecular light-harvesting systems constructed based on SS-FRET and TS-FRET are promising for chemical sensing leadership, information encryption, biomedical imaging, etc. These systems typically exhibit extremely large Stokes shifts, high quantum yields, and long-wavelength-emitting fluorescence (especially in the near-infrared) with tunable colors. This review summarizes cucurbit[n]urils-based supramolecular light-harvesting systems that restrict the rotation and vibration of organic fluorescent/phosphorescent molecules, and briefly discusses ALHSs based on other macrocyclic compounds and their functional applications. A wide range of cucurbit[n]urils are encompassed for practical reading value, including single-cavity Q[n]s, (n = 5–8, 10) and double-cavity tQ[13–15]) and ns-Q[10]). The rigid cavity structure and high affinity of Q[n]s could induce spatial confinement effects, which effectively limit or reduce the decay of radiative/non-radiative transitions, promote inter-system crossing, reduce the distance between donor-acceptor pairs, and effectively improve energy transfer efficiency. We contribute to the promotion of the further development of Q[n]s-based FRET systems by discussing and summarizing the advantages, importance, and functional applications of Q[n]s in the construction of FRET systems, e.g., tunable multicolor luminescent materials, information encryption/anti-counterfeiting, photocatalysis, and biologically targeted therapeutics/imaging.