Synergistic modulation of spin and fluorescence signals in a nano-Saturn assembled by a metallofullerene and cycloparaphenylene nanohoop

Spin-based interdisciplinary research has attracted considerable attention, and various applications in magnetic memory, quantum science, and precision measuring technology have been reported. In this study, we induced a fluorescence property in a spin-active molecule by supramolecular assembly and realized a synergistic modulation of its spin and fluorescence properties. A Saturn-shaped supramolecular complex was synthesized using a spin-active metallofullerene Sc₃C₂@C₈₀ with a fluorescent nanohoop of tetra-benzothiadiazole-based [12]cycloparaphenylene (TB[12]CPP), and its spin and fluorescence properties were comprehensively investigated. Temperature-dependent electron paramagnetic resonance (EPR) spectroscopy and fluorescence analyses were conducted. Synchronous changes in the EPR signals and fluorescence peaks were discovered in the temperature range of 170–290 K. Based on nuclear magnetic resonance observations and theoretical calculations, a temperature-dependent host–guest interaction between Sc₃C₂@C₈₀ and a nanohoop was demonstrated, which explained the synchronous changes in the EPR signals and fluorescence peaks for Sc₃C₂@C₈₀⊂TB[12]CPP. The application of Sc₃C₂@C₈₀ as a molecular spin system to probe the host–guest interaction was also evaluated. These results show that the supramolecular assembly can be used to design advanced spin systems coupled with optical and magnetic behaviors based on paramagnetic and luminescent molecules.