A Supramolecular Strategy to Modulate the Photoluminescence of Metallofullerenes via Motion-Induced Phosphorescence Attenuation

Yttrium-based metallofullerenes have attracted much attention due to their typical photoluminescence properties with thermally activated delayed fluorescence (TADF) and phosphorescence, which have the potential for photofunctional materials. In this work, a supramolecular strategy to modulate the TADF and phosphorescence of metallofullerene Y₃N@C₈₀ with a molecular nanoring is reported. A supramolecular complex Y₃N@C₈₀⊂[9]CPPH was first constructed by Y₃N@C₈₀ and a molecular nanoring of [9]CPPH. Temperature-dependent photoluminescence measurements revealed that Y₃N@C₈₀⊂[9]CPPH retains the characteristic TADF band at 700 nm and phosphorescence-dominated band at 738 nm, respectively. However, Y₃N@C₈₀⊂[9]CPPH shows significantly amplified TADF emission as well as decreased phosphorescence compared to that of pristine Y₃N@C₈₀. This phenomenon can be ascribed to the existing dynamic motion of Y₃N@C₈₀ inside the nanocavity of molecular nanoring, which could result in nonradiative decay of triplet states and suppress the phosphorescence emission finally. Density functional theory calculations of Y₃N@C₈₀⊂[9]CPPH were employed to illustrate the structure and excited states. Thus, this host-guest interaction provides a new strategy for tuning the photoluminescence of metallofullerene optical materials via motion-induced phosphorescence modulation.