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 Er ions, which has potential applications in telecommunications, optical devices and bioscience. In this manuscript, we report the construction of a supramolecular complex of metallofullerene ErN@C and cycloparaphenylene [12]CPP to adjust the near-infrared photoluminescence of ErN@C 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 ErN@C⊂[12]CPP. The electrochemical results of ErN@C⊂[12]CPP show the negatively shifted redox potentials compared to pristine ErN@C and the H NMR signals of ErN@C⊂[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 Er ions in ErN@C, with the characteristic emission peak of Er at 1.5 μm being broadened and enhanced in the ErN@C⊂[12]CPP complex, while the fluorescence lifetime of Er also becomes longer after assembly formation. Furthermore, the ErN@C guest also can influence the photoluminescence property of [12]CPP, whose emission peaks exhibit a slight blue-shift in the ErN@C⊂[12]CPP complex. This study illustrates that the outer nanoring can be employed to adjust the photoluminescence of the encapsulated Er ion in ErN@C.