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. 2024 May 30;15(26):10214-10220.
doi: 10.1039/d4sc02814g. eCollection 2024 Jul 3.

Selective recognition and enrichment of C70 over C60 using an anthracene-based nanotube

Hao Nian  1   2 , Song-Meng Wang  1 , Yan-Fang Wang  1 , Yu-Tao Zheng  1 , Li-Shuo Zheng  1 , Xiaoping Wang  1 , Liu-Pan Yang  3 , Wei Jiang  1 , Liping Cao  2
Affiliations

Selective recognition and enrichment of C70 over C60 using an anthracene-based nanotube

Hao Nian et al. Chem Sci. .

Abstract

Selective recognition and enrichment of fullerenes (e.g., C60 and C70) remains challenging due to the same diameter and geometrical similarity. Herein, we report a hexagonal anthracene-based nanotube (1) through a one-pot Suzuki-Miyaura cross-coupling reaction. With anthracene-based side walls and pyridine linkers, 1 features a nano-scale tubular cavity measuring 1.2 nm in diameter and 0.9 nm in depth, along with pH-responsive properties. Interestingly, the electron-rich 1 shows high binding affinity (K a ≈ 106 M-1) and selectivity (K s ≈ 140) to C70 over C60 in toluene, resulting from their different contribution of π-π interactions with the host. The protonation of 1 simultaneously alters the electronic properties within the nanotube, resulting in the release of the fullerene guests. Lastly, the selective recognition and pH stimuli-responsive properties of the nanotube have been utilized to enrich C70 from its low-content mixtures of fullerenes in chloroform.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Scheme 1
Scheme 1. (a) Representative samples of the host⊃C70 complexes. (b) Comparison of the sizes of C60 and C70. (c) The bent structure of the anthracene-dimer building block.
Fig. 1
Fig. 1. (a) Synthesis of 1 and its protonation. (b) Partial 1H NMR spectra of 1 (bottom) and (1 + 3H)3+ (top) in toluene-d8 at 298 K. The satellite peaks of solvents are indicated by the asterisk symbol.
Fig. 2
Fig. 2. X-ray structures of (1 + 3H)3+(TFA−)3: (a) top view and (b) side view of a single molecule; (c) side view of neighboring nanotubes inserted into each other; (d) top view of the structure of the packing nanotubes. For clarity, all counterions and solvent molecules are omitted. CCDC No.: 2323307.
Fig. 3
Fig. 3. (a) Partial 1H NMR spectra (500 MHz, toluene-d8, 298 K) recorded for (bottom) 1, (medium) 1 ⊃ C60, and (top) 1 ⊃ C70 ([1] = 2.0 mM; [C60 and C70] = 2.0 mM); (b) competitive 1H NMR experiment and association constant of 1 ⊃ C70; (c) experimental and simulated ESI mass spectra of 1 ⊃ C70.
Fig. 4
Fig. 4. (a) Electrostatic potential surface of 1, C60, and C70; non-covalent interaction analysis (using an independent gradient model based on Hirshfeld partition, IGMH) for (b) 1 ⊃ C70 and (c) 1 ⊃ C60, using the ωB97XD functional together with the Pople basis set; side view of the anthracene fragment and (d) C60 and (e) C70.
Fig. 5
Fig. 5. Schematic presentation and UV-vis spectra of the C70 enrichment process.
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