Visible and near-infrared photoluminescence of a supramolecular complex constructed from a cycloparaphenylene nanoring and an erbium metallofullerene

Erbium metallofullerenes exhibit near-infrared photoluminescence from the Er³⁺ ions, which has potential applications in telecommunications, optical devices and bioscience. In this manuscript, we report the construction of a supramolecular complex of metallofullerene Er₃N@C₈₀ and cycloparaphenylene [12]CPP to adjust the near-infrared photoluminescence of Er₃N@C₈₀ through host-guest interactions. Moreover, this supramolecular complex shows a multiwavelength luminescence property. Mass spectrometry, electrochemical measurements and proton NMR spectroscopy were used to characterize the structure of Er₃N@C₈₀⊂[12]CPP. The electrochemical results of Er₃N@C₈₀⊂[12]CPP show the negatively shifted redox potentials compared to pristine Er₃N@C₈₀ and the ¹H NMR signals of Er₃N@C₈₀⊂[12]CPP shift upfield compared to pristine [12]CPP. More importantly, the photoluminescence spectra show that the [12]CPP nanoring can affect the near-infrared emission of encapsulated Er³⁺ ions in Er₃N@C₈₀, with the characteristic emission peak of Er³⁺ at 1.5 μm being broadened and enhanced in the Er₃N@C₈₀⊂[12]CPP complex, while the fluorescence lifetime of Er³⁺ also becomes longer after assembly formation. Furthermore, the Er₃N@C₈₀ guest also can influence the photoluminescence property of [12]CPP, whose emission peaks exhibit a slight blue-shift in the Er₃N@C₈₀⊂[12]CPP complex.