Turning On the Near-Infrared Photoluminescence of Erbium Metallofullerenes by Covalent Modification

Abstract

The photoluminescence of lanthanide ions inside fullerenes is usually very weak due to the quenching effect of the fullerene cage. In the case of Er@C 82 , the near-infrared emission from the Er 3+ ion is completely quenched by the C 82 fullerene cage. It remains challenging to turn on the photoluminescence of Er@C 82 and other monometallofullerenes. In this work, we adopt a covalent modification strategy to alter the electronic structure of the fullerene cage for sensitizing the near-infrared emission of Er 3+ ions in metallofullerenes Er@C 2n (2n = 72, 76, and 82). After covalent modification with trifluoromethyl, phenyl, or dichlorophenyl groups, the erbium metallofullerenes exhibit photoluminescence at 1.5 μm, which is the characteristic emission of the Er 3+ ion. Particularly, the otherwise nonfluorescent metallofullerene Er@C 82 is transformed into fluorescent derivatives by using this strategy. The photoluminescence from the Er 3+ ion is ascribed to energy transfer from the fullerene cage to the Er 3+ ion. According to theoretical calculations, the sensitization of the Er 3+ ion by the fullerene cage is associated with the large HOMO−LUMO gap and the closed-shell electronic structure of the metallofullerene derivatives. This work provides useful guidance for the design and synthesis of new fluorescent metallofullerenes.

Theoretical Insight into Thermodynamically Optimal U@C84: Three-Electron Transfer Rather Than Four-Electron Transfer

“…The fluorescence from Th- and U-based EMFs has been previously reported. , It is also reported that, after covalent modification, the nonfluorescent and triplet mono-EMFs Er 3+ @C 2 n 3– (2 n = 72, 76, and 82), possessing open-shell electronic structures and one unpaired electron on the cage, with small band gaps can generate the signals of near-IR photoluminescence . Considering the several similarities, we reasonably deduced that thermodynamically stable U@C 84 isomers might also produce possible photoluminescence properties via the chemical modification method.…”

Metallofullerene photoswitches driven by photoinduced fullerene-to-metal electron transfer

“…The situation can be changed if endohedral metal atoms have low-energy emitting states, and near-infrared lanthanide-based luminescence had been observed in Er-and Tm-based EMFs. 19,[43][44][45][46][47][48] Surprisingly, Y 3 N@C 80 was found to show unusually strong luminescence and long uorescence lifetimes, but the reasons for this unexpected behaviour rst remained unclear. 49,50 Recently we found that the strong photoemission of Y 3 N@C 80 is caused by the small singlet-triplet S 1 -T 1 gap of less than 0.1 eV, which enables thermally activated delayed uorescence (TADF) via thermal population of the emitting S 1 state from the T 1 "reservoir".…”

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

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Erbium metallofullerenes exhibit near-infrared photoluminescence from the Er 3+ ions, which has potential applications in telecommunications, optical devices and bioscience. In this manuscript, we report the construction of a supramolecular complex of metallofullerene Er 3 N@C 80 and cycloparaphenylene [12] CPP to adjust the near-infrared photoluminescence of Er 3 N@C 80 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 Er 3 N@C 80 ⊂[12]CPP.

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“…The electrochemical results of Er 3 N@C 80 ⊂[12]CPP show the negatively shifted redox potentials compared to pristine Er 3 N@C 80 and the 1 H NMR signals of Er 3 N@C 80 ⊂[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 3+ ions in Er 3 N@C 80 , with the characteristic emission peak of Er 3+ at 1.5 μm being broadened and enhanced in the Er 3 N@C 80 ⊂[12]CPP complex, while the fluorescence lifetime of Er 3+ also becomes longer after assembly formation. Furthermore, the Er 3 N@C 80 guest also can influence the photoluminescence property of [12]CPP, whose emission peaks exhibit a slight blue-shift in the Er 3 N@C 80 ⊂[12]CPP complex.…”

“…Erbium metallofullerenes exhibit near-infrared photoluminescence from the Er 3+ ions, which has potential applications in telecommunications, optical devices and bioscience. In this manuscript, we report the construction of a supramolecular complex of metallofullerene Er 3 N@C 80 and cycloparaphenylene [12] CPP to adjust the near-infrared photoluminescence of Er 3 N@C 80 through host-guest interactions.…”